# PERCEPTIONS OF PEOPLE: CUES TO UNDERLYING PHYSIOLOGY AND PSYCHOLOGY

EDITED BY : Kok Wei Tan, Lisa L. M. Welling, Ian D. Stephen, Alex L. Jones and Danielle Sulikowski PUBLISHED IN : Frontiers in Psychology

#### Frontiers eBook Copyright Statement

The copyright in the text of individual articles in this eBook is the property of their respective authors or their respective institutions or funders. The copyright in graphics and images within each article may be subject to copyright of other parties. In both cases this is subject to a license granted to Frontiers. The compilation of articles constituting this eBook is the property of Frontiers.

Each article within this eBook, and the eBook itself, are published under the most recent version of the Creative Commons CC-BY licence. The version current at the date of publication of this eBook is CC-BY 4.0. If the CC-BY licence is updated, the licence granted by Frontiers is automatically updated to the new version.

When exercising any right under the CC-BY licence, Frontiers must be attributed as the original publisher of the article or eBook, as applicable.

Authors have the responsibility of ensuring that any graphics or other materials which are the property of others may be included in the CC-BY licence, but this should be checked before relying on the CC-BY licence to reproduce those materials. Any copyright notices relating to those materials must be complied with.

Copyright and source acknowledgement notices may not be removed and must be displayed in any copy, derivative work or partial copy which includes the elements in question.

All copyright, and all rights therein, are protected by national and international copyright laws. The above represents a summary only. For further information please read Frontiers' Conditions for Website Use and Copyright Statement, and the applicable CC-BY licence.

ISSN 1664-8714 ISBN 978-2-88963-748-5 DOI 10.3389/978-2-88963-748-5

#### About Frontiers

Frontiers is more than just an open-access publisher of scholarly articles: it is a pioneering approach to the world of academia, radically improving the way scholarly research is managed. The grand vision of Frontiers is a world where all people have an equal opportunity to seek, share and generate knowledge. Frontiers provides immediate and permanent online open access to all its publications, but this alone is not enough to realize our grand goals.

#### Frontiers Journal Series

The Frontiers Journal Series is a multi-tier and interdisciplinary set of open-access, online journals, promising a paradigm shift from the current review, selection and dissemination processes in academic publishing. All Frontiers journals are driven by researchers for researchers; therefore, they constitute a service to the scholarly community. At the same time, the Frontiers Journal Series operates on a revolutionary invention, the tiered publishing system, initially addressing specific communities of scholars, and gradually climbing up to broader public understanding, thus serving the interests of the lay society, too.

#### Dedication to Quality

Each Frontiers article is a landmark of the highest quality, thanks to genuinely collaborative interactions between authors and review editors, who include some of the world's best academicians. Research must be certified by peers before entering a stream of knowledge that may eventually reach the public - and shape society; therefore, Frontiers only applies the most rigorous and unbiased reviews.

Frontiers revolutionizes research publishing by freely delivering the most outstanding research, evaluated with no bias from both the academic and social point of view. By applying the most advanced information technologies, Frontiers is catapulting scholarly publishing into a new generation.

#### What are Frontiers Research Topics?

Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office<EMAIL_ADDRESS>
# PERCEPTIONS OF PEOPLE: CUES TO UNDERLYING PHYSIOLOGY AND PSYCHOLOGY

Topic Editors:

Kok Wei Tan, University of Reading Malaysia, Malaysia Lisa L. M. Welling, Oakland University, United States Ian D. Stephen, Macquarie University, Australia Alex L. Jones, Swansea University, United Kingdom Danielle Sulikowski, Charles Sturt University, Australia

Citation: Tan, K. W., Welling, L. L. M., Stephen, I. D., Jones, A. L., Sulikowski, D., eds. (2020). Perceptions of People: Cues to Underlying Physiology and Psychology. Lausanne: Frontiers Media SA. doi: 10.3389/978-2-88963-748-5

# Table of Contents

*05 Editorial: Perceptions of People: Cues to Underlying Physiology and Psychology*

Danielle Sulikowski, Kok Wei Tan, Alex L. Jones, Lisa L. M. Welling and Ian D. Stephen

*08 Evidence That the Hormonal Contraceptive Pill is Associated With Cosmetic Habits*

Carlota Batres, Aurélie Porcheron, Gwenaël Kaminski, Sandra Courrèges, Frédérique Morizot and Richard Russell

*13 The Relationship Between Observers' Self-Attractiveness and Preference for Physical Dimorphism: A Meta-Analysis*

Lijun Chen, Xiaoliu Jiang, Huiyong Fan, Ying Yang and Zhihong Ren

*65 Facial Adiposity, Attractiveness, and Health: A Review* Stefan de Jager, Nicoleen Coetzee and Vinet Coetzee

*81 The Influence of Body Composition Effects on Male Facial Masculinity and Attractiveness*

Xue Lei, Iris J. Holzleitner and David I. Perrett

Amany Gouda-Vossos, Robert C. Brooks and Barnaby J. W. Dixson

*157 Roar of a Champion: Loudness and Voice Pitch Predict Perceived Fighting Ability but Not Success in MMA Fighters* Pavel Šebesta, Vít Třebický, Jitka Fialová and Jan Havlíček

# Editorial: Perceptions of People: Cues to Underlying Physiology and Psychology

Danielle Sulikowski 1 \*, Kok Wei Tan2 , Alex L. Jones 3 , Lisa L. M. Welling4 and Ian D. Stephen5,6,7

 *Perception and Performance Research Group, School of Psychology, Charles Sturt University, Bathurst, NSW, Australia, School of Psychology and Clinical Language Sciences, University of Reading Malaysia, Gelang Patah, Malaysia, Department of Psychology, College of Human and Health Sciences, Swansea University, Swansea, United Kingdom, Psychology Department, Oakland University, Rochester, MI, United States, 5 Department of Psychology, Macquarie University, Sydney, NSW, Australia, 6 Perception in Action Research Centre, Macquarie University, Sydney, NSW, Australia, Body Image and Ingestive Behaviour Group, Macquarie University, Sydney, NSW, Australia*

Keywords: mate quality signals, health, fertility, formidability, person perception

#### **Editorial on the Research Topic**

#### **Perceptions of People: Cues to Underlying Physiology and Psychology**

Our perceptual sensitivity to cues of socially and sexually relevant physiological and psychological traits in others is remarkable. For such sensitivity to evolve, the directly perceptible qualities of others (which include intrinsic physical traits, such as height, weight, body odor, facial morphology, and body shape; as well as behaviorally modified appearance cues, such as those produced by clothing and makeup; and vocal parameters) must afford at least somewhat accurate judgements of others' health, fertility, formidability, personality, or other fitness-relevant capacities. The current issue examines whether a variety of perceptible qualities present potentially valid cues of underlying physiology and psychology, and/or the extent to which such cues support adaptive judgements of others.

 Sexual dimorphism (masculinity in male faces and femininity in female faces) is one on the most studied aspects of facial morphology (for review, see, e.g., Little et al., 2011) and its importance in mate relevant choices is again highlighted in the current issue. Facial morphological correlates of bodily muscle mass in male faces predict female perceptions of facial masculinity; and such correlates are perceived as more attractive for short-term relationships, and less attractive for long-term relationships by said women (Lei et al.).  Preferences for highly sexually dimorphic partners are thought to be condition-dependent, reflecting a trade-off made by higher quality individuals, which compromises kind, caring personalities (especially in less masculine men) in favor of more sexually dimorphic, genetically robust individuals. Consistent with this theory, Chen et al. also report a reliable (though small) positive association between own attractiveness and preferences for sexual dimorphism (especially in women rating men as longterm partners, and men rating women as short-term partners). Šterbová et al. ˇ reported that women's long-term partner preferences are generally highly stable from one relationship to the next, with one exception: facial masculinity. The facial masculinity of participants' long-term partners varied more than expected by random coupling—the only trait of 21 measured to do so. In addition, long-term partners with whom the participants had children also had more masculine faces than non-fathers.

Edited and reviewed by: *Peter Karl Jonason, University of Padova, Italy*

\*Correspondence: *Danielle Sulikowski<EMAIL_ADDRESS>
#### Specialty section:

*This article was submitted to Evolutionary Psychology, a section of the journal Frontiers in Psychology*

Received: *29 February 2020* Accepted: *17 March 2020* Published: *08 April 2020*

#### Citation:

*Sulikowski D, Tan KW, Jones AL, Welling LLM and Stephen ID (2020) Editorial: Perceptions of People: Cues to Underlying Physiology and Psychology. Front. Psychol. 11:643. doi: 10.3389/fpsyg.2020.00643*

Beyond sexual dimorphism, facial adiposity, and skin color are also important cues to physical and physiological health. Facial adiposity is a highly reliable indicator of body mass index and numerous health outcomes (most notably those associated with being overweight or obese; de Jager et al.). Across cultures and ethnicities, skin yellowness (which indicates the presence antioxidant carotenoids), and to a lesser extent skin redness (an indicator of blood flow associated with physical fitness and levels of sex hormones) are subjectively perceived by observers as indicators of physical health (Tan and Stephen). Cues to physiological health, especially anaerobic capacity, may also be present in human faces. Judgements of the fighting ability of mixed martial arts fighters, based on 360◦ headshots, were jointly predicted by the fighters' weight and anaerobic capacity (Trebick et al.). Although this study took advantage of the additional information available in a 360◦ headshot compared to a single front-on portrait, Trebick et al. also demonstrated that attractiveness and formidability judgements of front-on, profile, and 360◦ portraits differ very little in terms of their means, and are strongly inter-correlated. This observation bolsters many conclusions drawn from across the field of evolutionary psychology of face perception, many of which are based on judgements of single front-on portraits.

The judgments we make of human faces may also influence how we perceive non-human primate faces. Primate faces that are least like human faces are perceived as the most beautiful (Rádlová et al.), an effect attributed to the uncanny valley (i.e., the hypothesized relationship between resemblance to humans and emotional response; e.g., Mori et al., 2012). The more like human faces primate faces become, however, the more that human-face predictors of attractiveness judgements (in terms of the exact arrangements of the internal features), also predicted the beauty judgements of the primate faces.

New data-driven methods for analyzing facial morphology have also been presented in this Research Topic. Mogilski and Welling present a novel application of data-driven conjoint analysis showing that eyebrow thickness, jaw prominence, and facial height exhibit superior signaling capacity for judgements of sexual dimorphism and attractiveness compared to other regions of the face. Kleisner et al. proposed a new method for measuring cultural typicality and cross-cultural distinctiveness of faces. Based on calculating an individual face's exact position on the vector connecting the facial morphological averages of the two cultures being compared, Kleisner et al. were able to predict significant variance in faces' perceived distinctiveness. They also demonstrated that in-group/out-group judgements were easier (in a two-alternative forced-choice design) when the out-group face was furthest away from the in-group mean. Both of these novel methodologies open the door for more nuanced analyses of the signaling capacity of human facial morphology.

Non-morphological, behavioral cues, including vocalizations and body odor, also provide information about their bearer. Single men, compared to partnered men, exhibit stronger body odor, and based on their body odor alone are judged by women to be more masculine (Mahmut and Stevenson). Listeners also adjust their perceptions of another based on the pitch of vocalizations. Mixed martial arts fighters are judged to be more formidable if their roars (spontaneous vocalizations made when victorious) are higher pitched, and also if their speaking voice is lower pitched (Šebesta et al.). Similarly contrasting effects of pitch are observed when comparing singing and speaking voices. The perceived attractiveness of singing and speaking strongly correlate across individuals, and both predict physical size in men (Valentova et al.). Also in men, low-pitched speech, but higherpitched singing, predict higher sociosexuality. In women, shorter apparent vocal tract length (indicated by shorter spacing between the first four formant frequencies) in speech, but longer apparent vocal tract length during singing, predicted higher sociosexuality (Valentova et al.). It therefore appears that both pitch and range of vocalizations provide important cues as to the quality of potential mates and competitors.

Extended phenotypic traits, manifesting beyond the bearer's physical body, may also constitute socially meaningful cues. Two such adornments include clothing and make-up. Gouda-Vossos et al. investigated how wearing business vs. casual attire influenced perceptions of men's and women's socio-economic status. Business attire increases the perceived economic status of men more than it does for women, while the perceived economic status of women is increased if depicted in business attire alongside a group of men (whereas the economic status of men is not increased by being depicted among a group of women). The consequences of such judgements for interpersonal interactions are not known. Women use cosmetics to alter their physical appearance and this can affect their perceived attractiveness. Batres et al. observed that women using the contraceptive pill spend less time putting on make-up for an outing than do naturally cycling women, and that such women are indeed perceived as wearing more make-up. This finding adds to the breadth of behaviors in which circulating sex hormones are implicated (see Welling and Shackelford, 2019), although the complexities of female cosmetics use, what it signals, and how it is perceived remain to be thoroughly investigated.

The methods used by evolutionary psychologists to understand how the multitude of physical and behavioral cues we possess are signaled and received were also a focus of critique within this special issue (see Bovet; Kleisner et al.; Trebick et al.). Bovet reviewed the literature concerning women's waist-to-hip ratios and criticized the weak theoretical foundations of the area. Highlighting the large number of potential signaling functions of the waist-to-hip ratio and the small number of studies designed to specifically differentiate between the competing theories, Bovet cautions against rushing into empirical work without first establishing a clear theoretical basis to guide empirical robustness and consistency. Doing so can lead to imprecise, untestable predictions and seemingly contradictory results, leading to the premature rejection of potentially legitimate theories based on findings of objectively low evidentiary value.

Cues and signals of physiology, behavior, and personality exist in faces, bodies, voices and our extended phenotypes. For many such potential cues, we have demonstrated objective links between the putative cue and the underlying quality it may indicate; observed receiver sensitivity to such cues; or put forward coherent adaptive and mechanistic theories accounting for how such cues may come to signal these qualities in the first place (in either a proximate or ultimate sense). For this area of person perception to continue to move forward, concerted efforts are needed to address all three of the above outcomes for each individual cue-quality-receiver system. By triangulating objective relationships between cues and qualities, the impact of such cues on receiver psychology, and sophisticated mechanistic, functional, and adaptive theories to explain the evolution and

## REFERENCES

maintenance of these systems, we will amass a body of work with great potential impact for understanding modern human social, romantic, and sexual interactions.

## AUTHOR CONTRIBUTIONS

DS was the primary author of the first draft. All authors contributed to revisions and corrections of the final manuscript.

**Conflict of Interest:** The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2020 Sulikowski, Tan, Jones, Welling and Stephen. This is an openaccess article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

# Evidence That the Hormonal Contraceptive Pill Is Associated With Cosmetic Habits

Carlota Batres1,2 \*, Aurélie Porcheron3,4, Gwenaël Kaminski5,6, Sandra Courrèges3 , Frédérique Morizot3 and Richard Russell1

1 Department of Psychology, Gettysburg College, Gettysburg, PA, United States, 2 Department of Psychology, Franklin and Marshall College, Lancaster, PA, United States, 3 CHANEL Fragrance & Beauty Research & Innovation, Pantin, France, 4 Laboratoire de Psychologie et NeuroCognition, Université Pierre Mendès-France, Grenoble, France, 5 CNRS (UMR 5263), Cognition, Langues, Langage, Ergonomie, Université de Toulouse, Toulouse, France, 6 Institut Universitaire de France, Paris, France

Hormonal contraception is known to cause subtle but widespread behavioral changes. Here, we investigated whether changes in cosmetic habits are associated with use of the hormonal contraceptive pill. We photographed a sample of women (N = 36) who selfreported whether or not they use the contraceptive pill, as well as their cosmetic habits. A separate sample of participants (N = 143) rated how much makeup these target women appeared to be wearing. We found that women not using the contraceptive pill (i.e., naturally cycling women) reported spending more time applying cosmetics for an outing than did women who use the contraceptive pill. We also found that the faces of these naturally cycling women were rated as wearing more cosmetics than the faces of the women using the contraceptive pill. Thus, we found clear associations between contraceptive pill use and makeup use. This provides evidence consistent with the possibility that cosmetic habits, and grooming behaviors more generally, are affected by hormonal contraception.

Keywords: cosmetics, makeup, contraception, birth control, grooming behaviors

## INTRODUCTION

The hormonal contraceptive pill is used by approximately 100 million women worldwide (Christin-Maitre, 2013). Its main function is to change the hormonal state of the menstrual cycle in order to mimic, and thus prevent, pregnancy (Alvergne and Lummaa, 2010). While the majority of women take the contraceptive pill to prevent pregnancy, approximately 14% of women use it for other reasons, such as for lessening menstrual pain and migraines (Cooper and Adigun, 2017).

In addition to its medical side effects, the contraceptive pill has also been linked to several behavioral effects (Welling et al., 2012). For example, one study found that married women not using the contraceptive pill (i.e., naturally cycling women) showed an increase in female-initiated sexual behavior at the time of ovulation, whereas women using the contraceptive pill did not show such a rise (Adams et al., 1978). Other studies have also found that the hormonal state of the contraceptive pill changes women's partner preferences. For instance, unlike naturally cycling women, one study found that those using the contraceptive pill prefer less masculine male faces (Little et al., 2002, but see Jones et al., 2018).

Research has also found that the contraceptive pill affects women's ability to attract mates. For example, one study found that for naturally cycling women, their voices became more attractive as

#### Edited by:

Alex L. Jones, Swansea University, United Kingdom

#### Reviewed by:

Benedict C. Jones, University of Aberdeen, United Kingdom Danielle Leigh Wagstaff, Federation University, Australia

\*Correspondence:

Carlota Batres<EMAIL_ADDRESS>
#### Specialty section:

This article was submitted to Evolutionary Psychology, a section of the journal Frontiers in Psychology

Received: 22 May 2018 Accepted: 24 July 2018 Published: 23 August 2018

#### Citation:

Batres C, Porcheron A, Kaminski G, Courrèges S, Morizot F and Russell R (2018) Evidence That the Hormonal Contraceptive Pill Is Associated With Cosmetic Habits. Front. Psychol. 9:1459. doi: 10.3389/fpsyg.2018.01459

**8**

their risk of conception increased but no such effect was found for women using the contraceptive pill (Pipitone and Gallup, 2008). One field study examined the tip earnings of professional lap dancers and found that those who were naturally cycling made more money per shift than those who were using the contraceptive pill (Miller et al., 2007).

In this study, we aimed to examine whether the use of the contraceptive pill also influences grooming behaviors, particularly cosmetic habits. Previous research has found that among naturally cycling women, the time spent putting on cosmetics, and the rated level of cosmetics used by women, seems to be higher near ovulation (Guéguen, 2012). No study, however, has examined whether there is a difference in cosmetic habits between naturally cycling women and women using the contraceptive pill. Previous research has shown that, unlike women using the contraceptive pill, naturally cycling women change their appearance near ovulation to look more attractive (Haselton et al., 2007; Durante et al., 2011). Given that makeup is one way that women can alter their attractiveness (Graham and Jouhar, 1981; Jones et al., 2015; Jones and Kramer, 2016; Batres et al., 2018), we predicted that naturally cycling women would report spending more time applying cosmetics, and would be rated as wearing more cosmetics, than women using the contraceptive pill.

## STUDY 1

## Methods

#### Participants and Procedure

Thirty six women (M age = 19.58 years, SD = 2.14) completed the study. The participants were recruited at the University of Grenoble using advertisements and obtained financial compensation to participate in the study. The research was performed in accordance with the Declaration of Helsinki: it was conducted with the understanding and the written consent of each participant (who were instructed that their photographs would be taken) and was approved by local ethics boards (CNRS and the University of Grenoble).

After arriving at the laboratory, 20 min were allowed to pass in order to allow the participants' skin to acclimatize to the indoor temperature. Photographs were then taken of each participant facing forward, under constant camera/lighting conditions, with neutral expressions, and closed mouths. Each participant also completed a questionnaire in which she reported whether she was taking hormonal contraceptives, if so, what type of hormonal contraceptives (e.g., the contraceptive pill, an intrauterine device), whether she had regular menstrual cycles, and whether she was in a relationship. All 36 women reported having regular menstrual cycles. Twenty women reported not using any hormonal contraceptives (i.e., naturally cycling) and 16 women reported using hormonal contraceptives, out of which 100% reported using the contraceptive pill.

Each participant also completed two questions pertaining to her cosmetic habits: how much time she spent on her daily makeup in the morning and how much time she spent making up for an outing. These two questions allowed us to define two variables concerning cosmetic habits: daily cosmetics and outing cosmetics. To examine the association between contraceptive pill use and cosmetic habits, we performed independent samples t-tests on both cosmetic habits variables.

#### Results

Naturally cycling women reported spending more time applying cosmetics (both daily and for an outing) than women using the contraceptive pill (see **Figure 1**). The difference between naturally cycling women and women using the contraceptive pill was not statistically significant for the amount of time they spent on their daily cosmetics, t(33) = 1.59, p = 0.121, Cohen's d = 0.51, but it was statistically significant for the amount of time they spent on their cosmetics for an outing, t(19.6) = 2.30, p = 0.033, Cohen's d = 0.80.

## STUDY 2

## Methods

#### Participants and Procedure

One hundred and forty three Gettysburg College students participated in Study 2 (M age = 18.53 years, SD = 0.87, 56 male, 87 female) as part of a course requirement. Ethical approval was received from the Gettysburg College Institutional Review Board. Participants were instructed that they would be viewing and rating face images on a computer. Participants were asked to rate each face on the question: "How much makeup does this face have?," where 1 = Very little makeup and 7 = A lot of makeup. The faces presented were those of the women from Study 1. To examine the association between pill use and perceived amount of cosmetics, we performed a linear mixed model.

#### Results

Due to repeated measurements, we included the target faces and the participants as random effects. Naturally cycling women

FIGURE 1 | In minutes, reported amount of time spent applying daily cosmetics in the morning and reported amount of time spent making up for an outing, for both naturally cycling women (i.e., those not using the contraceptive pill) and women using the hormonal contraceptive pill. The asterisk indicates a significant difference (∗p < 0.05). Error bars indicate the standard error of the mean.

were rated as having higher levels of cosmetics [3.65 (3.24–4.06)] than women using the contraceptive pill [2.79 (2.43–3.17)] (see **Figure 2**). We found that the difference in amount of perceived cosmetics between naturally cycling women and women using the contraceptive pill was statistically significant [χ2(1) = 8.86, p = 0.003, β = 0.85 [0.31–1.39)].

## DISCUSSION

The results from Studies 1 and 2 provide the first evidence that the use of the hormonal contraceptive pill is associated with cosmetic habits. In Study 1, we found that naturally cycling women spent more time applying cosmetics for an outing than women using the contraceptive pill. On average, naturally cycling women reported spending an extra 13 min applying cosmetics for an outing than women using the contraceptive pill. Naturally cycling women also reported spending more time applying their daily cosmetics than women using the contraceptive pill, but this difference was not statistically significant. In Study 2, we found that the faces of the naturally cycling women (taken during the day) were rated by participants as having higher amounts of cosmetics than the faces of the women using the contraceptive pill. This suggests that while naturally cycling women may not spend more time applying their daily makeup, they use more visible cosmetics. These findings thus provide evidence that contraceptive pill use is associated with cosmetics use.

This is consistent with previous research suggesting that naturally cycling women are found more attractive than women using the hormonal contraceptive pill (Miller et al., 2007). Our study, however, proposes that part of such difference in attractiveness may be due to cosmetics. In other words, naturally cycling women may, in part, be found more attractive than women using the contraceptive pill because they wear more cosmetics, which greatly increases attractiveness (Graham and Jouhar, 1981; Batres et al., 2018). For instance, Miller et al.'s (2007) study found that naturally cycling lap dancers had higher tip earnings than those using the contraceptive pill, but part of that difference may be explained by a change in the amount of cosmetics worn by the dancers. Indeed, research has observed that waitresses receive higher tips when they are wearing cosmetics compared to when they are not (Jacob et al., 2009). This suggests it is likely that different makeup use explains part of the differences in attractiveness found between naturally cycling women and women using hormonal contraception.

Our results may also point to a larger issue: that the contraceptive pill may be associated with behavioral changes that affect women's grooming practices more generally, of which cosmetics is just one part. In other words, the contraceptive pill may suppress how women adorn themselves, otherwise referred to as the extended phenotype (Etcoff et al., 2011). Some studies have examined how the extended phenotype changes throughout the menstrual cycle. For instance, one study found that selfgrooming and ornamentation through attractive choice of dress increased during high fertility periods (Haselton et al., 2007). However, a recent longitudinal study did not find evidence for fertility-linked changes in women's clothing choices (Arslan et al., 2017). Similar studies are needed to compare the extended phenotype of women who are using the contraceptive pill and those that are not. Such research would shed light on whether cosmetic habits are the only form of ornamentation influenced by the contraceptive pill or whether it is just one facet of a greater behavioral shift in how women present themselves (e.g., grooming, jewelry, clothing).

Our study did not control the phase of the menstrual cycle in which women were photographed nor asked how long the women had been using or not using the contraceptive pill and therefore future research should control for this. We also did not define what was meant by an outing and the interpretation of this could have had some impact on self-reported time spent applying cosmetics. For example, women may have reported less time if an outing was interpreted as going out for dinner versus if it was interpreted as going out to a club. Future studies would therefore benefit from being more specific when asking about time spent applying cosmetics for an outing. Similarly, while we asked the women how much time they spend on their daily makeup in

the morning, it would have been helpful to ask how much time they spent making up that exact morning in order to better link cosmetics application time with perceptual differences. Moreover, adding other measures of cosmetics use would also be beneficial in future studies (e.g., "How natural does the makeup on this face look?"). Women who are skilled at perfecting the "natural" look are likely to spend more time applying cosmetics but may appear to be wearing less makeup.

Further research is still needed to better understand links between the contraceptive pill and cosmetic habits as our study was a non-randomized between-subjects design and research has found that naturally cycling women and women using the contraceptive pill differ in other ways (Alexander et al., 1990). For example, Little et al. (2002) found that women using the contraceptive pill reported having more lifetime sexual partners than naturally cycling women. A related concern is that in our study only 19% of naturally cycling women reported being in a relationship, while 85% of women using the contraceptive pill reported being in a relationship. Our sample was too small to include relationship status as a factor in our analyses and thus future research with a larger sample is needed. No study has examined differences in cosmetic habits between single women and women in a relationship, however, such a difference could very well be possible. In order to address these two concerns and confirm the link between the contraceptive pill and cosmetic habits, an experimental design, rather than the correlational one used here, would be needed. More specifically, women would need to be randomly assigned to use or not use the contraceptive pill in order to be able to establish a casual effect between the contraceptive pill and cosmetic habits. However, such an experiment is unlikely due to ethical reasons, which is why the current literature has relied on non-randomized betweensubjects designs (e.g., Adams et al., 1978; Little et al., 2002; Miller et al., 2007; Pipitone and Gallup, 2008; Welling et al., 2012).

#### CONCLUSION

In conclusion, we found that, compared to women using the contraceptive pill, naturally cycling women self-reported

#### REFERENCES

spending more time applying cosmetics for an outing, and their faces were rated as having higher levels of cosmetics. These results provide initial evidence that the contraceptive pill is associated with cosmetic habits. Moreover, this association may be part of a broader relationship between contraceptive pill use and other grooming behaviors, stemming from hormone-mediated changes in motivations.

## ETHICS STATEMENT

The experiments were undertaken with the understanding and written consent of each subject, with the approval of the appropriate local ethics committees, and in compliance with national legislation and the Code of Ethical Principles for Medical Research Involving Human Subjects of the World Medical Association (Declaration of Helsinki).

### AUTHOR CONTRIBUTIONS

CB, AP, GK, FM, and RR conceived and designed the research. CB and GK acquired the data. CB, GK, and RR analyzed the data. CB, AP, GK, SC, and RR interpreted the results. CB drafted the work. CB, AP, GK, SC, and RR critically revised the paper. CB, AP, GK, SC, FM, and RR approved the final version to be published and agreed to be accountable for the content of the work.

## FUNDING

The research was funded in part by CHANEL Fragrance & Beauty Research & Innovation.

## ACKNOWLEDGMENTS

We thank Lucille Brunero for help with collecting data for this manuscript.

Evol. Hum. Behav. 28, 375–381. doi: 10.1016/j.evolhumbehav.2007. 06.002

**Conflict of Interest Statement:** AP, FM, and SC work at CHANEL Fragrance & Beauty Research & Innovation, a cosmetics company, and CB and RR receive funding from CHANEL Fragrance & Beauty Research & Innovation.

The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2018 Batres, Porcheron, Kaminski, Courrèges, Morizot and Russell. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

# The Relationship Between Observers' Self-Attractiveness and Preference for Physical Dimorphism: A Meta-Analysis

Lijun Chen1,2, Xiaoliu Jiang1 , Huiyong Fan3 , Ying Yang1 and Zhihong Ren4,5 \*

*1 School of Humanities and Social Sciences, Fuzhou University, Fuzhou, China, 2 Institute of Psychological and Cognitive Sciences, Fuzhou University, Fuzhou, China, 3 College of Teacher, Bohai University, Jinzhou, China, 4 Key Laboratory for Adolescent Cyberpsychology and Behavior of the Education Ministry, Wuhan, China, 5 Laboratory of Human Development and Mental Health, Institute of Psychology, Central China Normal University, Wuhan, China*

Background: Many studies have reported an association between observers' self-attractiveness and their preference for sexual dimorphism across different physical domains, including the face, voice, and body. However, the results of these studies are inconsistent. Here, a meta-analysis was conducted to estimate the association between observers' own attractiveness and their dimorphic preference.

## Edited by:

*Lisa L. M. Welling, Oakland University, United States*

#### Reviewed by:

*Anthony Little, University of Bath, United Kingdom Nicole Barbaro, Oakland University, United States Lei Chang, University of Macau, China*

> \*Correspondence: *Zhihong Ren<EMAIL_ADDRESS>
#### Specialty section:

*This article was submitted to Evolutionary Psychology, a section of the journal Frontiers in Psychology*

Received: *15 June 2018* Accepted: *19 November 2018* Published: *05 December 2018*

#### Citation:

*Chen L, Jiang X, Fan H, Yang Y and Ren Z (2018) The Relationship Between Observers' Self-Attractiveness and Preference for Physical Dimorphism: A Meta-Analysis. Front. Psychol. 9:2431. doi: 10.3389/fpsyg.2018.02431* Methods: Major electronic databases including PsycINFO, Web of Science, PubMed, ProQuest, and Google Scholar were searched during April 2017 (the first time) and April 2018 (the second time). The effect size computation and moderating effect analyses were conducted separately for masculine and feminine preferences.

Results: We identified 5,359 references, of which we included 25 studies (*x* = 55, *x* = number of the effect size) with 6,853 participants in the meta-analysis. Across these studies, the correlation between observers' own attractiveness and their sexual dimorphic preference was 0.095 (*x* = 55) and that for preference for masculinity (*x* = 39) and femininity (*x* = 16) were 0.102 and 0.076, respectively. The results of the funnel plot, Egger's regression method, and fail-safe number suggested that there was no obvious publication bias. The relationship depended on the relationship context (short or long-term), opposite or same sex (the gender of the observer and host), measures of observers' self-attractiveness (subject or objective), and preference task (e.g., attractiveness rating, forced-choice, and face sequence test). Furthermore, for female participants, using a hormonal contraceptive also influenced their masculinity preference. The effect size for the preference for a masculine body and voice was larger than that for facial masculinity.

Conclusion: We found a small but significant correlation between self-attractiveness and physical dimorphic preference, the relationship was moderated by the relationship context, same/opposite-sex, and contraceptive using. These three moderating effects represented the observer's trade-off on good genes, good provider and good father (3Gs) consistent with the life history strategies. Besides, measurement of observers' attractiveness, type of preference task and stimuli may also involve the relationship.

  Sexually dimorphic physical traits are important for mate choice and mate preference in many species, including humans. Several previous studies have observed that humans' preferences for physical cues of extreme secondary sexual characteristics (more feminine for women, more masculine for men) in different domains (e.g., visual, vocal, and bodily) are correlated (Little et al., 2007; Fraccaro et al., 2010). These correlations demonstrate a systematic, rather than arbitrary, variation in humans' preferences for sexual dimorphism, which are consistent with the proposal that sexually dimorphic cues in different domains reflect a common underlying aspect of quality. On the evolutionary view, femininity of women, masculinity of men are proposed to be more attractive because they advertise the good genes of an individual (Rhodes, 2006). Among humans, physical characteristics consistent with the owner's gender are correlated with indices of long-term health (Rhodes et al., 2003; Thornhill and Gangestad, 2006), reproductive potential (Puts, 2005; Rhodes et al., 2005), and low parasite loadings and high immune competence (Thornhill and Gangestad, 1993, 1996), but negatively correlated with prosociality (Haselton, 2005; Haselton and Gangestad, 2006). Men's masculine traits indicate untrustworthiness and bad parental traits (Boothroyd et al., 2007; Smith et al., 2009b), and women's femininity are considered as more likely to be unfaithful, to pursue short-term relationships, and to be in higher risk of cuckoldry (Little et al., 2014).

According to the life history (LH, referring to organisms capturing energy from the environment and using it to produce more organisms) trade-off model strategies in mating choice (Gangestad and Simpson, 2000; Del Giudice and Belsky, 2011), women focused on two types of characteristics when they chose a mate: those indicating a "good provider" (social-economic characteristics, such as wealth, education, career) and "good genes"(physical characteristics) (Gangestad and Buss, 1993; Gangestad and Simpson, 2000). Other researchers believed that the framework of women's mate preference should involve three Gs. Besides good genes, good providers, women also prioritize a man's personality traits—for example, being kind, loving, and staying at home—that constitute good fathers (Buss and Shackelford, 2008; Lu et al., 2015). Good provider indicate men have resource to invest in parenting, traits of good father can reflect men's intention to help raising young, both of the two types of characteristics represent parenting of reproductive effort in post mating events (parental investment), otherwise good genes characteristics were realized as mating attributes affecting premating decisions. When exposed to contrasting environments, women would have evolved to make trade-offs between investment qualities and indicators of good genes contingent on specific environmental conditions, because good genetic males tend to have more mates at the same time, and they invest in each female than in males of lower phenotypic quality, women's emphasis on good genes may be at the cost of men's parental investment (Gangestad and Simpson, 2000). Men also encounter trade-off problems, because, while feminine females possess high attractiveness and good genes, they are also associated with negative personality characteristics (unfaithful) (Haselton, 2005; Haselton and Gangestad, 2006), and men also have expectations about maternal investment. For both men and women (but more for men than women), parental warmth and care (good father or mother) correlated negatively with good-gene and good-provider mate values (Chang et al., 2017). Both men and women encounter the tradeoff of 3Gs mating framework.

Therefore, preferences for dimorphism represent the result of trading off between good genes and parental investment. Differences in how humans resolve this trade-off can lead to individual differences in sexual dimorphic preference. For example, attractive women demonstrate stronger preferences for masculine men than relatively unattractive women do (Little et al., 2001; Little and Mannion, 2006). These are called condition-dependent preferences. In the evolution of species, condition-dependent preferences have been observed in many species, in which individuals in good physical condition tend to show stronger preferences for high-quality mates (Bakker et al., 1999). Condition-dependent preferences in both humans and non-humans may have a common function and they may occur because individuals in good physical condition (i.e., attractive individuals) are better able to compete for and/or retain highquality mates (Little et al., 2001). Additionally, they can offset the costs of choosing a partner with good genes (e.g., by being able to replace a partner more quickly), and therefore, they improve their criteria for mate selection. On the contrary, in order to meet the needs of parental investment, individuals with poor self-conditions may reduce their standards for mate selection, and they prefer mates who are more likely to make high parental investment. The following findings appear to be somewhat analogous to condition-dependent preferences observed in humans. Women's ratings of their own physical attractiveness positively correlated with the strength of their preferences for masculine characteristics in men's faces (Little et al., 2001; Penton-Voak et al., 2003; Smith et al., 2009b). Similar correlations have been found in men's voices (Vukovic et al., 2008, 2010) and bodies (Little et al., 2007). Further, the concept of condition-dependent preferences is conceptualized as "market value dependent preferences": when exposure to attractive samesex images, women perceived themselves less attractiveness and lower prefer for male facial masculinity; whereas exposure to unattractive same-sex images, they perceived themselves more attractiveness and lower prefer for masculinity (Little and Mannion, 2006).

There is inconsistent evidence on the relationship between observers' own attractiveness and their sexual dimorphic preference. While some experimental results have confirmed that attractive females prefer masculine faces (Smith et al., 2009b; Welling et al., 2009; Kandrik and DeBruine, 2012), others did not find such a relationship (Zietsch et al., 2015; Carrito et al., 2016). However, several studies have found that observers' own attractiveness can interact with other variables and impact their preferences (Little et al., 2001; Smith et al., 2009a; Burriss et al., 2011; Chen et al., 2017).

## Influence of Relationship Context in the Preference of Opposite-Sex

The context in which judgments are made can also contribute to differences in the relationship between dimorphic preference and the observer's self-attractiveness (Little et al., 2001, 2002; Penton-Voak et al., 2003; Carrito et al., 2016). There are two types of relationship context: short-term and long-term. The former refers to a sexual relationship, such as a one-night stand; the latter is a lasting relationship, such as being married. The tradeoff theory proposed that contextual factors affect the strength of people's preferences for a masculine or feminine partner (Gangestad and Simpson, 2000). Attractive women prefer more masculine male faces than less attractive women do, and this difference is seen in the context of a long- but not a shortterm relationship (Penton-Voak et al., 2003). This result has been supported by several studies across voice and body stimuli (Little et al., 2007; Feinberg et al., 2012). Otherwise, attractive men exhibit stronger preferences for feminine women only in the short-term context (Burriss et al., 2011; Little et al., 2014). As feminine women were seen as more likely to be unfaithful and more likely to pursue short-term relationships (Boothroyd et al., 2008), and the risk of cuckoldry limit men's preferences for femininity in women and that it could additionally lead to preferences for femininity in short-term mates (Little et al., 2014). Thus, we supposed that the influence of attractiveness on male masculine preferences is more pronounced in the long-term than in the short-term context for women, but for men, the effect of attractiveness on female feminine preference is more prominent in the short-term context.

## Observer's Age and Contraceptive Using

It has been found that reproductively active women had the strongest preference for males' masculinity (Little et al., 2010; Jones et al., 2011), and another study only observed the age effect in women using no contraception (Little et al., 2002). Some studies have found that hormonal contraceptive use may modulate individual differences in women's masculinity preference (Little et al., 2002; Feinberg et al., 2008; Smith et al., 2009a). Furthermore, Vukovic et al. (2008) found that self-rated attractiveness was positively related to the strength of women's preference for masculinized men's voices in women reporting no use of hormonal contraceptives, but not in those using the same. Actually, effects of female observer's age and contraceptive using both due to their physiological hormone levels. Because females of different ages are in different reproductive stages with different hormone levels. And women using hormonal contraceptives are in a hormonal state similar to pregnancy, and consequently, they are unable to realize the benefits that are thought to be associated with choosing a masculine mate (i.e., increased offspring health) (Smith et al., 2009a). In light of the previous studies, we speculate that attractive-contingent preference is stronger in women who do not use hormonal contraceptives than in those who do.

## Measures of Observer's Own Attractiveness

Initially, researchers used self-rated items to determine observers' own attractiveness. Little et al. (2001) used self-reported attractiveness as an indicator of observers' own attractiveness and found that attractive females preferred masculine male faces; Little and Mannion (2006) found that women's subjective impressions of their own market value (i.e., their self-rated attractiveness) is particularly important with reference to the effects of attractiveness on women's masculinity preferences. However, other researchers failed to confirm these findings (Cornwell et al., 2006). Therefore, some researchers have questioned the veracity of subjective assessments, and began to adopt objective measures of self-attractiveness in experiments (Penton-Voak et al., 2003). These objective measures included other-rated facial attractiveness, waist-to-hip ratio (WHR), and body mass index (BMI) (Penton-Voak et al., 2003; Smith et al., 2009b). found that women with high WHR (an indicator of unattractiveness) and/or relatively low other-rated facial attractiveness preferred more feminine male faces when choosing males for a long-term relationship. This result has been confirmed by another study (O'Connor et al., 2012). Then, what kind of measurement (subjective or objective) would be more sensitive to self-attractiveness? In the current study, we examined the moderating role of the measurement of observers' own attractiveness (subjective/objective) and compared the effect sizes of the measurements in this relationship.

Thus, evidence on the relationship between observers' self-attractiveness and preference for sexual dimorphism is equivocal. This is potentially because the preference is conditiondependent. Therefore, we can conclude that observers' selfattractiveness is an important variable that interacts with other variables such as measuring methods, relationship context, same/opposite-sex, and contraceptive use (yes or no) to influence observers' dimorphic preferences. Based on the LH trade-off model strategies and condition-dependent preference, the metaanalysis technique was used in the present meta-analysis to investigate whether observers' sexual dimorphic preferences vary across their self-attractiveness, and to interpret the possible reasons for the divergence. We focused on the following two core issues: What is the totally coefficient of the relationship between the two variables? Which factors moderate their relationship significantly?

## METHODS

## Information Sources and Search

The following search terms were used in combination: sexual dimorphism, masculin∗ , feminin∗ , fac∗ , bod∗ , vocal, voice, and attractiveness. Search terms for observers' own attractiveness included self-rated attractiveness, self-perceived attractiveness, self-reported attractiveness, self-perceptions of attractiveness, selfratings of attractiveness, other-rated attractiveness, and thirdparty attractiveness ratings. Major electronic databases, including PsycINFO, Web of Science, PubMed, ProQuest, and Google Scholar were searched during April 2017(the first time) and April 2018 (the second time). The reference lists of the included studies were searched to identify additional studies.

## Eligibility Criteria and Study Selection

Only studies that met the following three criteria were included: ➀ The relationship between the sexual dimorphic preference and observer's self-attractiveness was investigated in the study. ➁ Specific data on this relationship were accurately reported in the study (such as the correlation coefficients r; mean; standard deviation; sample size; or corresponding F, t, or χ 2 ) to enable the calculation of the effect size, excluding the data of the structural equation model, path analysis, and multivariate regression analysis. In order to avoid missing important literature, we wrote to the authors (first or corresponding author) to obtain the correlation coefficient if it was not reported in the article. ➂ In cases where there were multiple reports of the same study, we used the first published report. Two authors independently screened the titles and abstracts of the identified articles to exclude ineligible studies. Disagreements were resolved by discussion. We retrieved the full text of the potentially eligible studies and examined full-text reports for further evaluation. The PRISMA flow diagram (Moher et al., 2010) represents all the steps of the literature search (see **Figure 1**).

## Summary Measures

In psychological research, the standard mean difference (d) and correlation coefficient (r) are frequently used to compute effect sizes. In order to integrate the relationship between the sexual dimorphic preference and observers' own attractiveness, the correlation coefficient (r) was used in the present meta-analysis. In some primary studies correlation coefficients can be retrieved from t, F, or χ 2 which reported. The following formulas were used in this context (Card, 2012):

$$\begin{aligned} r &= \sqrt{\frac{t^2}{t^2 + df}}, \, df = n\_1 + n\_2 - 2 \,; r = \sqrt{\frac{F(1, -)}{F(1, -) + df(error)}} ; \\ r &= \sqrt{\frac{\chi^2}{\chi^2 + N}}. \end{aligned}$$

After extracted, all correlations were transformed using Fisher's Z-transformation (Lipsey and Wilson, 2001). The sample distribution of Zr is approximately equal to the normal distribution (Hittner and Swickert, 2006; Borenstein et al., 2009). The formula for the transformation is as follows: Zr = 0.5 × ln( 1+r 1−r ). The overall Zr can be computed through weighted Zr. Then the overall r can be found through an inverse operation of Fisher' Z-transformation (Lipsey and Wilson, 2001; Borenstein et al., 2009). These computation related to overall effect size estimation were conducted under the random-effects model (Borenstein et al., 2009). The specialized statistical software Comprehensive Meta-Analysis (CMA, Version 2.2) was used in the current meta-analysis for conducting all the needed computations and analyses.

## Data Extraction

Two authors extracted the following information: first author's name, year of publication, sample size of observers, observers' age, gender of the stimuli (male or female), observers' gender (male or female), facial attractiveness task (the forced-choice test with an attractiveness rating, the forced-choice test alone, or the face sequence test), sexual dimorphic preference (masculinity or femininity), measures of observers' own attractiveness (objective or subjective), type of stimuli (face, voice, body), and use of contraceptive (yes or no; for female observers only).

Considering that the sexual dimorphic preference is divided into masculine preference and feminine preference, and that the correlation between observers' own attractiveness and their masculine or feminine preferences is opposite, this meta-analysis calculated the effect sizes and conducted moderating effect analyses for masculine and feminine preferences separately. The data is available in **Supplementary Table 1**.

## Heterogeneity Test

The heterogeneity test was conducted to test whether the average effect size was heterogeneous. Each effect size of each observation value in this meta-analysis contained real and residual effect sizes, which resulted in the partial false phenomenon of effect sizes. The heterogeneity test of effect sizes is always examined by calculating the Q statistic (Borenstein et al., 2009) and I 2 (Card, 2012). In this systemic review, the two statistical values of I 2 and Q were used to detect the heterogeneity of the included effect sizes.

## Publication Bias

Publication bias is a concern for any meta-analytic review because it can lead to a larger combined effect than what actually exists. This type of bias refers to the phenomenon where published studies are more likely to report larger effects. Because studies that have not been published due to their negative or null findings are more difficult to retrieve, and therefore, are less likely to be included in a meta-analysis, an upward bias in the combined effect may occur. Furthermore, English-language publication are more likely to be searched, which leads to an oversampling of statistically significant studies. In this meta-analysis, we use a variety of methods to minimize and test publication bias. When searching the literature, we also searched the most popular and diverse Chinese database CNKI (China National Knowledge Infrastructure), the conference and the dissertation database; and wrote to the important researchers in this field to ask if they had any unpublished research reports. When analyzing the data, we used the funnel plot, Egger's regression and Rosenthal's Fail-safe N to evaluate the publication bias and the degree of its impact (Borenstein et al., 2009).

## RESULTS

## Description of Studies and Overall Association

Due to the topic involved self-attractiveness and dimorphic preference two variables, we combined 7 terms describing preference (face, voice and body) and 6 terms describing observer's attractiveness to search, our literature searches initially identified 5,359 potential articles from databases, but most of them were unrelated articles; Additionally, in many related studies, they involved the relationship between dimorphic

preference and self-attractiveness, whereas, they did not look the relationship as an important topic and not describe in the titles, abstracts, keywords, we also searched the references and citing articles of the related studies, which resulted in many duplicates. Finally the current meta-analysis included 25 studies with 6,853 participants (see **Table 1**). The flow chart has been presented in **Figure 1**. The 25 eligible studies produced 55 effect sizes because 12 studies consisted of multiple datasets. We examined the relationship between preference for sexual dimorphism and observers' own attractiveness. The results showed that the correlation coefficientr (x = 55) of the relationship between these two variables was 0.095 (95% CI: 0.059, 0.130; Z = 5.173, p < 0.001). The correlation coefficient r of the relationship between observers' own attractiveness and preference for masculinity (x = 39) and femininity (x = 16) were 0.103 (95% CI: 0.060, 0.146; Z = 4.691, p < 0.001) and 0.076 (95 % CI: 0.007, 0.145, Z = 2.162, p = 0.031< 0.05), respectively. According to Lipsey and Wilson (2001), an effect size r lower than 0.10 indicates a weak correlation. In order to check the stability of the results of the mean effect size analyses, we conducted a sensitivity analysis, which showed that this meta-analysis did not need to eliminate any of the data that had been included. The data is available in **Supplementary Table 2**.

### Heterogeneity Test

The overall heterogeneity test (x = 55) showed Q = 145.567 (p <0.001), I 2 = 62.904, that mean there existed moderate heterogeneity (Higgins et al., 2003). For masculine preferences, the result of the heterogeneity test (x = 39) showed Q = 72.93 (p < 0.001), I 2 = 47.90 (moderate heterogeneity). For feminine preferences, the result of the heterogeneity test (x = 16) showed Q = 71.77 (p <0.001), I 2 = 79.10 (high heterogeneity).

Considering that previous studies have shown heterogeneity of sexual dimorphic preferences (Wood et al., 2014), and according to Borenstein et al. (2009), if the true effect varies across studies using different samples, it is more reasonable to use the random model.  Therefore, the random model was more suitable for the present meta-analysis.

## Publication Bias

We could not find any Chinese published researches in the CNKI database, and none of the important researchers said they have unpublished researches on this topic. We used the funnel plot, Egger's regression and Rosenthal's Fail-safe N to evaluate the publication bias of the studies included in this meta-analysis. In the absence of publication bias, the studies will be distributed symmetrically about the mean effect size, since the sampling error is random. Otherwise, if the funnel plot is asymmetrical at the bottom, there may be publication bias. The funnel plots in the current analysis are a little asymmetrical at the bottom (see **Figures 2**–**4**). Because the interpretation of a funnel plot is largely subjective, the Egger's method has been proposed to quantify or test the publication bias (Egger et al., 1997). So, Egger's method was conducted to detect the publication bias, the result is that t(47) = 1.39, p = 0.17, which means there is no significant bias. Our current meta-analysis reported a significant p-value based on 25 studies. According to Rosenthal's suggestion,

#### TABLE 1 | Characteristics of the 25 studies included in the present meta-analysis.

*(Continued)*

#### TABLE 1 | Continued

we should compute how many missing studies we would need to retrieve and incorporate in the analysis before the p-value became non-significant, the number of the missing studies was called Rosenthal Fail-safe N. The larger number of studies that are needed to nullify the effect, the more confident we can be of a real effect (Rosenthal, 1979). The result of Fail-safe N showed that at least 973 studies with the opposite conclusions would be required to overturn the findings of this meta-analysis.

### Subgroup Analysis

Given the moderate heterogeneity of effect sizes and influence factors aforementioned in the introduction, we conducted subgroup analyses to examine whether the effect sizes varied according to measures of observers' self-attractiveness, type of stimulus, tasks of preference and same/opposite-sex stimuli. The present meta-analysis included only one effect size of same-sex feminine preferences in male stimuli and none of masculine preferences in female stimuli. Thus, we conducted subgroup analysis on feminine preferences for female stimuli and masculine preferences for male stimuli for the same-opposite sex analysis. Moreover, in masculine preference, all the effect sizes on relationship context and contraceptive use were extracted from the preference of opposite-sex (female preference for male stimulus); in feminine preference, all the data on relationship context also came from the preference of opposite-sex (male preference for female stimulus). The results of the subgroup analysis have been presented in **Table 2**. The moderated analysis showed that, for masculine (x = 39), task of preference, measures of observers' self-attractiveness, type of stimulus affected the association between observers' self-attractiveness and their masculine preferences, additionally, women's preference for male masculinity varied across contraceptive use/no and shortlong term relationship context. And for feminine preference (x = 16), this association also depended on the task of preference, relationship context, same/opposite-sex stimuli.

#### Meta-Regression Analysis

To assess the influence of observers' age, published year, and sample size of observers on the effect size (r coefficient), considering these three variables are continuous, meta-regression analysis were carried out for masculine preference and feminine preferences separately. Firstly, we looked the effect size of relationship between self-attractiveness and masculine preference as dependent variable. The results showed the effect size decreased with observers' age, published year, and sample size of observers (see **Table 3**). Specifically, the older observers were, the more negative relationship between self-attractiveness and masculinity preference. In other words, in younger people, individuals in high physical condition would more prefer masculinity. Further, the larger the sample size of the study, the weaker was this relationship, and the later the publishing year of the study, the smaller was the effect. Subsequently, the effect size of relationship between self-attractiveness and feminine preference was used as dependent variable. Only the publishing year significantly positively influenced the relationship.

 However, the empirical evidence is inconsistent. The present meta-analysis provides a quantitative synthesis of the available evidences on the attractive-contingent preference, and reveals a significant overall relationship (r = 0.095, x = 55). Additionally, selfattractiveness is significantly positively but weakly related with masculine and feminine preference (masculinity: r = 0.102, x = 39; femininity, r = 0.076, x = 16). These findings are consistent with the concept of condition-dependent preference. Condition dependence lies at the heart of the trade-off between costly sexual traits and other major fitness components such as survival and growth. Variability among individuals' physical condition can potentially influence the form, direction, and intensity of sexual selection in the population as a whole (Widemo and Sæther, 1999). Some previous studies have confirmed that highquality females were more attracted to markers of quality in males (masculine men) across different domains (face, voice, body, and smell) (Little et al., 2011b), which is due to the fact that their own high attractiveness means that lower parental investment is less detrimental. Actually, there is a more complex relationship between self-condition and mating choice, as selfattractiveness does not occur in isolation (Little et al., 2014). The objective or subjective measurement of self-attractiveness (Smith et al., 2009b), relationship context of preference for opposite-sex stimuli (Little et al., 2007; Kandrik and DeBruine, 2012), type of stimuli would also play an important role in observers' sexual dimorphic preferences.

## The Influence of Same/Opposite-Sex, Relationship Context, Contraceptive Use: Basing on the Life History Tradeoff Strategies

As shown in **Table 2**, the intensity of attractive-contingent preference did change across same/opposite-sex conditions, which is inconsistent with our hypothesis. In masculine preference for male stimulus, the correlation between women's self-attraction and male masculine preference was stronger than that of men's self-attraction (opposite = 0.107, x = 35; same = 0.066, x = 3). Patterns of women preferences for men's masculine features are more complex (Burke and Sulikowski, 2010; Holzleitner and Perrett, 2017). On the viewing of LH strategies, good genes, and good provisioning male mate attributes evolved mainly from polygyny: muscularity in men indicating higher immune competence, physical attractiveness, and dominance, competition, high status, but they attract and tend to have more female mates at the same time, and they invest less in each female. In spite of this, attractive women are more confident and believe that they can offset the costs of choosing good genes and good providing partner (Little et al., 2001). Although, attractive men more likely to prefer masculine men as social allies, self-rated sex typicality is the

stronger trait to predict preference for sex-typical physical cue in same-sex faces (Kandrik and DeBruine, 2012), and appears to be more important influence factor of men's preference for same-sex physical cues. Moreover, the market value (good physical condition) is potentially a more important resource for women's mating choice than for men's cooperative choice (Kandrik, 2017). Otherwise, When it comes to the preference for female femininity, the influence of same-sex is greater than that of opposite-sex (same = 0.219, x = 3; opposite = 0.083, x = 7), in another word, attractive women showed a more obvious trend than men did. Possibly because more attractive women may perceive less threat from other feminine women and more likely to look them as social allies (Fisher, 2004). While Attractive men tend to choose charming women but also trade off the benefit and the cost of cuckoldry. Therefore, men's choices also depend on the context of the relationship (long or short term) (Burriss et al., 2011; Little et al., 2014).

In line with our expectations, on women's preferences in male masculinity, long-term context had a larger effect size as compared to the short-term context (correlation in the shortterm context was 0.001, x = 9; that in the long-term context was 0.228, x = 9). Attractive women expressed preferences for all three clusters of men's mate characteristic (3Gs) (Buss and Shackelford, 2008), as the aforementioned conflict of good genes, good provider and good father, they have to trade off. Women placed more value on man's physical attractiveness, muscularity and immediate resource displays (Haselton and Gangestad, 2006) when pursuing short-term mating, in contrast, they placed greater importance on resource acquisition potential and good dad indicators when pursuing long-term mating (Buss and Shackelford, 2008; Lu et al., 2015). In the context of short-term sexual relationships, the perceived cues to high parental investment in feminine men are of little value to women. Moreover, women of higher/lower physical condition can extract potential benefits from masculine men by copulating and conceiving with a short-term relationship. And therefore, both attractive and unattractive females trade on good genes (masculinity) in short-term context. On the contrary, in longterm relationships, better parenting and increased cooperation may outweigh the benefits of genetic fitness, thereby enhancing the attractiveness of more feminine males (Little and Mannion, 2006). Highly attractive women think that they are good enough to find another partner soon, and therefore, they do not need to be restricted by the real conditions or change their preferences according to the relationship context. However, women with poorer appearance have to trade off good genes and parental investment in the long-term context. As a result, the attractivecontingent masculine preference appeared more apparent in the long- than in the short-term context. A similar trend was observed in the voice domain (Feinberg et al., 2012).

On men's preference for women's femininity, the effect size for the short-term context was larger as compared to that for the long-term context (short-term = 0.202, x = 2; longterm = 0.081, x = 3), which indicated that attractive men were more strongly attracted by feminine female in shortterm relationship than unattractive men, however, in long-term context, the men's self-attractiveness wasn't closely associated to their preference for femininity. Firstly, on the perspective of LH tradeoff strategies, preferences represent various LH strategies: fertility-related attributes (good genes) represent a fast LH strategy, whereas attributes of good parenting serve as slow LH function (Lu et al., 2017). Attractive men tended to adopt fast LH strategies with feminine women in short-term relationship, reported more short-term partners than less attractive men TABLE 2 | Summary of the results of the sub-group meta-analysis.

*x, number of effect sizes; MOOA, Measures of Observers' Own Attractiveness; RC, Relationship Context; FCT and AR, Forced-choice Test and Attractiveness Rating; FCT, Forced-choice Test; ST, Sequence Test;* \*\*\**p* < *0.001,* \*\**p* < *0.01,* \**p* < *0.05.*

(Rhodes et al., 2005). As without regards to raising the young, their attractiveness primed them with chance to produce greater number of offspring. Secondly, unlike women trading off between man's good gens and his resource, willing to invest, a man risked raising a child which is not his own, they mainly traded on partner's physical attractiveness and personality traits in longterm relationship (Little et al., 2014). Because feminine women are perceived as unfaithful and are considered more likely to have an affair or a brief sex trade. Both attractive and unattractive men considered women's risk of cuckoldry carefully in long-term contexts, such that self-attractiveness seemed less related with femininity preferences (Little et al., 2014).

The analysis of the moderating effect showed that the correlation coefficient for the relationship of the self-reported attractiveness of non-users of contraceptives and their masculinity preference was significantly higher than that of users (0.183 vs. 0.093). A cross-sectional longitudinal study confirmed that hormonal contraceptive users had a weaker preference for masculinity than non-users did (Little et al., 2013), which was consistent with the findings of other previous studies (Roberts et al., 2014). In addition, hormonal contraceptives tended to decrease women's overall physical attractiveness (Puts and Pope, 2013; Welling, 2013; Roberts et al., 2014), and as discussed above, women's attractiveness was their "market

value" and an important factor in "intra-sexual competition." Therefore, by diminishing women's attractiveness, hormonal contraceptives might make it more difficult for women to compete for romantic partners (Smith et al., 2009a; Puts and Pope, 2013). Similarly, effect size was more negatively correlated with observers' age in masculine preference (see **Table 3**). The observers in the present analysis pool for masculine preference were females. In other words, younger attractive women preferred masculine faces. As people age, especially women, they recalibrate subjective impressions of their own attractiveness (i.e., impressions of their own "market value"), which, in turn, leads to a recalibration of their mate preferences (Little et al., 2011a). With a decrease in their market value with age, most women pay attention to parental characteristics (Jones et al., 2011).

#### Type of Stimuli

With reference to feminine preferences, because the present meta-analysis included only one study on vocal and none on body stimuli, we examined the moderating role of stimuli type in masculine preference. This analysis revealed significantly different effect sizes for body, voice, and face stimuli. Specifically, the effect sizes for voice and body were larger than that for face stimuli (body = 0.185, x = 2; voice = 0.184, x = 8; face = 0.078, x =29), the effect sizes of body and voice are close to 0.2, a moderate amount. However, the coefficient of face and masculine preference was 0.078, a weak correlation, which was out of our expectation. Previous studies have interpreted covariation as evidence that different domains of masculinity all advertised a common underlying factor. Additionally, we suggested that men's and women's masculinity, as signaled by multiple traits, were related to some common information about the underlying quality of the observed individual. Of course, this did not mean that the signals overlap perfectly (Little et al., 2011a), and indeed, our data suggests that masculine preference in all the three traits was strongly related to observers' self-attractiveness. This indicates a distinct characteristic. Masculine facial preferences are less relevant to self-attractiveness, potentially because a large number of studies have focused on facial masculine preference, while little attention has been paid to the preference for masculinity in the voice and body of the observed. Furthermore, most of these studies on facial preferences regarded self-attractiveness as a covariant, and they explored its interaction with other main variables (e. g., relationship context or menstrual cycle). Evidently, the correlation varied in different conditions, and therefore, more effect sizes of facial masculine preference (x = 29) averaged into a smaller effect size.

## The Task of Preference and Measures of Self-Attractiveness

Stronger effects were found when the sequence test (ST) was used instead of using the forced-choice test (FCT) with an attractiveness rating (Masculinity: ST = 0.183 x = 11; FCT = 0.081, x = 12; Femininity: ST= 0.125 x = 6; FCT = 0.076, x = 6). The sequence test provides observers a program in which they can regulate the sexual dimorphism independently until they reached the level that they considered most attractive (Carrito et al., 2016). The forced-choice test with an attractiveness rating merely provides observer two dimensions of a face (masculine and feminine) to choose from. They must then choose one that they consider more attractive and rate its attractiveness (Little and Mannion, 2006). Thus, the sequence test is more ecological and it reflects the observer's preference for dimorphism more clearly.

Most studies included in the present meta-analysis focused on masculine preferences and none used an objective index to measure feminine preferences. Thus, we conducted this subgroup analysis only on masculine outcomes. A moderator analysis revealed a significant difference in the effect sizes of masculine preferences according to the measures of selfattractiveness, which is consistent with Penton-Voak et al.'s findings (Penton-Voak et al., 2003). They thought objective measures could be independent from menstrual cycle, and would be more stable than self-assessments are (Penton-Voak et al., 2003). Some researchers have emphasized that BMI and WHR were better indicators of female attractiveness (Swami et al., 2007; Smith et al., 2009b). Similarly, in the current meta-analysis, objective attractiveness was highly related to masculine preferences (effect size = 0.133, x = 13), but selfrated attractiveness showed a weak relationship (effect size = 0.069, x = 26). Most of the participants were female in the studies included in this meta-analysis. Subjective measures may be influenced by their individual physiology, for example, women perceived themselves more attractive when ovulating (Singh et al., 2001), and self-rated attractiveness may potentially fluctuate in a short space of time. Self-report measures are subjective and may not reflect how an individual is perceived by others. Therefore, objective measurements such as WHR, BMI, and other-rated attractiveness may be more sensitive to the relationship between self-attractiveness and sexual dimorphic preferences.

### LIMITATIONS

We would like to mention some limitations of the present metaanalysis. The first concerns the number of studies analyzed. We included 25 studies, which were divided into sets based on feminine and masculine preferences before submitting them to separate meta-analyses. This meant that we had a limited number of studies for each moderator level (see **Table 2**). Therefore, some levels of the moderator were under-represented. The second limitation of the current meta-analysis is that the age range of observers was relatively concentrated, in that most of them were teenagers or young individuals in their 20s, and only two studies selected older subjects with an average age of 33 years (Zietsch et al., 2015) and 48 years (Jones et al., 2011). Therefore, although the results of the present study revealed a significant regulatory effect of age, the accuracy of this correlation is difficult to prove.

## CONCLUSIONS

This meta-analysis suggests that there is a real relationship between sexual dimorphic preferences and observers' selfattractiveness. Therefore, in future studies, researchers should control self-attractiveness to ensure the reliability of experimental results. According to the results of the present subgroup analyses, this relationship depends on relationship context, same/oppositesex, and contraceptive using. These three moderating effects represented the observer's trade-off on 3Gs, were consistent with the life history strategies. Besides, measurement of observers' attractiveness, type of preference task and stimuli may also may involve the relationship. Therefore, in future studies, researchers should consider these factors and their interactions.

## REFERENCES

## AUTHOR CONTRIBUTIONS

LC and ZR co-designed the study and wrote the manuscript. LC and YY conducted the literature searches, the studies selection. LC and XJ took charged. LC, XJ and HF analysied the data. LC and ZR wrote the manuscript. XJ and LC revised according the review.

## FUNDING

This work was supported by the National Social Science Foundation of China (Grant No. CEA150173).

## ACKNOWLEDGMENTS

We would like to acknowledge Dr. Robert P. Burriss (Department of psychology, Basel University, Basel, Switzerland) for his comments for the manuscript.

## SUPPLEMENTARY MATERIAL

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpsyg. 2018.02431/full#supplementary-material

attraction to facial characteristics. Philos. Trans. R. Soc. Lond B Biol. Sci. 361, 2143–2154. doi: 10.1098/rstb.2006.1936

to sexual self-labels and attitudes toward masculinity. Arch. Sex. Behav. 45, 725–733. doi: 10.1007/s10508-015-0543-z

Zietsch, B. P., Lee, A. J., Sherlock, J. M., and Jern, P. (2015). Variation in women's preferences regarding male facial masculinity is better explained by genetic differences than by previously identified context-dependent effects. Psychol. Sci. 26, 1440–1448. doi: 10.1177/0956797615591770

**Conflict of Interest Statement:** The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2018 Chen, Jiang, Fan, Yang and Ren. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

# The Relative Contribution of Jawbone and Cheekbone Prominence, Eyebrow Thickness, Eye Size, and Face Length to Evaluations of Facial Masculinity and Attractiveness: A Conjoint Data-Driven Approach

#### Justin K. Mogilski1 \* and Lisa L. M. Welling2

#### Edited by:

Achim Schuetzwohl, Brunel University London, United Kingdom

#### Reviewed by:

R. Nathan Pipitone, Florida Gulf Coast University, United States Darren Burke, University of Newcastle, Australia

> \*Correspondence: Justin K. Mogilski<EMAIL_ADDRESS><EMAIL_ADDRESS>
#### Specialty section:

This article was submitted to Evolutionary Psychology, a section of the journal Frontiers in Psychology

Received: 10 September 2018 Accepted: 19 November 2018 Published: 05 December 2018

#### Citation:

Mogilski JK and Welling LLM (2018) The Relative Contribution of Jawbone and Cheekbone Prominence, Eyebrow Thickness, Eye Size, and Face Length to Evaluations of Facial Masculinity and Attractiveness: A Conjoint Data-Driven Approach. Front. Psychol. 9:2428. doi: 10.3389/fpsyg.2018.02428 1 Department of Psychology, University of South Carolina Salkehatchie, Walterboro, SC, United States, 2 Department of Psychology, Oakland University, Rochester, MI, United States

Recent work demonstrates the methodological rigor of a type of data-driven analysis (i.e., conjoint analysis; CA), which accounts for the relative contribution of different facial morphological cues to interpersonal perceptions of romantic partner quality. This study extends this literature by using a conjoint face ranking task to predict the relative contribution of five sexually dimorphic facial shape features (jawbone and cheekbone prominence, eyebrow thickness, eye size, face length) to participants' (N = 922) perceptions of facial attractiveness and sex-typicality (i.e., masculinity/femininity). For overall partner attractiveness, eyebrow thickness and jawbone prominence were relatively more salient than cheekbone prominence and eye size. Interestingly, masculinized (i.e., thicker) eyebrows were marginally more attractive for female than male faces, particularly within a long-term mating context. Masculinized jawbone prominence was more attractive for male than female faces, and feminized jawbone prominence was more attractive for female than male faces. For perceptions of masculinity, eyebrow thickness, jawbone prominence, and facial height were relatively more salient than cheekbone prominence and eye size, although facial height was more important for female than male faces, and jawbone prominence was marginally more important for male than female faces. These findings highlight the prominence of eyebrows, the jawline, and facial height during perception of facial attractiveness and masculinity – though it should be noted that many of these differences were small to moderate in effect size. Findings are interpreted in the context of prior research, and future directions for studying why these facial traits exhibit superior signaling capacity are discussed.

Keywords: face preference, face shape, masculinity, attractiveness, conjoint analysis, data-driven, digital manipulation

## INTRODUCTION

fpsyg-09-02428 December 3, 2018 Time: 11:4 # 2

Facial morphological cues (e.g., shape, color, and texture) are indicators of underlying physiology (Stephen et al., 2009; Little et al., 2011b; Jones et al., 2012). From these cues, humans can accurately predict certain physical and psychological qualities (e.g., an individual's health, physical attractiveness, trustworthiness) that are significant to partner selection and social judgment (e.g., Zebrowitz, 2011; Todorov et al., 2015). These qualities can be assessed by observers from facial photographs at first acquaintance, and significantly impact employment decisions, mate selection, friendship, and other key aspects of social interaction (e.g., Petrican et al., 2014; Walker and Vetter, 2016; Funk et al., 2017). Face perception researchers have studied how these cues are processed during interpersonal evaluation by digitally manipulating photographic facial cues and presenting these images to third-party raters. These manipulations predictably alter perceptions of attractiveness, dominance, sex-typicality (i.e., masculinity/femininity), health, trustworthiness, and other social attributes (for a review, see Todorov et al., 2008; Little et al., 2011a). However, this research has tended to focus on individual facial cues in isolation, and debate is now turning to the relative contributions of these cues to social perception (Scott et al., 2010; Stephen et al., 2012; Mogilski and Welling, 2017).

Data-driven models are becoming more valued within scientific face perception research for their capacity to account for a broader array of structural and configural facial features, and the contributions of those specific features to social perception, compared to traditional methods alone (Todorov et al., 2011; Zhang et al., 2018). Early studies that used digital face stimuli to alter and assess person perception (e.g., Perrett et al., 1999; Penton-Voak et al., 2001) measure the influence of perceptually distinct facial cues (e.g., symmetry and sexual dimorphism) by digitally altering one feature while experimentally or statistically controlling for variation in other features. Although this work makes compelling contributions to the literature by reducing confounds, it tells us little about how collections of traits are evaluated in combination. Recent data-driven techniques have overcome this limitation by permitting distinct clusters of features to be altered simultaneously (e.g., Mogilski and Welling, 2017; Stephen et al., 2017; Jones, 2018). For example, Stephen et al. (2017) recorded participants' physiological health (i.e., blood pressure, BMI, percent body fat) and regressed these measures onto variation in facial morphology. These measures were then subjected to factor analysis to identify which clusters of facial features predict variation in health. Participants were asked to change the appearance of potential romantic partners' facial photographs to fit their preference using sliders that incrementally altered faces along each health dimension, thereby digitally manipulating the constellation of facial features naturally associated with variation in these health indices. Similarly, Jones (2018) recorded participants' self-reported health and implemented a Brunswick lens model to assess which facial cues are utilized to assess health, and which cues are valid indicators of health. Photographs were subsequently manipulated according to whichever cues were most utilized and valid. Compared to prior techniques, these methods identify facial cues and manipulate them via digital transformations that are based on a broad collection of naturalistic features, rather than from artificially restricted parameters based on theory alone.

Although these models have been particularly useful for initially exploring, identifying, and simulating the facial cues that contribute to person perception and social decision-making, they are limited in their capacity to assess the relative contribution of several concurrently altered facial cues to holistic perception of those faces. In the studies noted above (Stephen et al., 2017; Jones, 2018), digital transformations were applied to facial images and rated sequentially rather than concurrently. For example, Stephen et al. (2017) asked participants to manipulate a series of faces to appear as healthy as possible by manipulating apparent BMI, blood pressure, and body fat, but each of these dimensions was manipulated independently and rated across separate trials. Jones (2018) manipulated two features concurrently (i.e., averageness and color), but asked participants to assess stimuli of different combinations (e.g., high averageness, low color) across separate line-ups of faces. These methods allow researchers to examine preference for feature combinations, but they are limited by how many feature combinations may be examined at the same time without separating them into separate trials or experimental conditions.

## Conjoint Analysis

Conjoint analysis (CA) provides a convenient way to overcome this design challenge. CA is a multivariate, data-driven analysis used in marketing research (e.g., Gustafsson et al., 2007) that has recently been adapted to study human mate preferences (Mogilski et al., 2014; Mogilski and Welling, 2017). Generally, CA is used to assess how individuals make trade-offs among multiple attributes when evaluating "whole" units that comprise those attributes. For example, CA is often used to evaluate which attributes of a product are most important during consumer purchasing decisions by having consumers rank several versions of the product, where each version is composed of a unique combination of product attributes. Mogilski and Welling (2017) first used this technique to examine the relative salience of three facial cues (i.e., sexual dimorphism, color, and symmetry) during romantic partner perception. Compared to other methods, this technique allows researchers to present sets of faces wherein each face is altered by several different features at once. Participants rank these sets on some metric (e.g., their attractiveness as a romantic partner) and CA provides measures of the relative contribution of each feature to participants' overall ranking decisions. Using this technique, Mogilski and Welling (2017) found that facial shape masculinity/femininity was relatively more important than both symmetry and color cues to health during participants' evaluations of potential romantic partners' facial photographs. However, presenting individuals with multiple versions of mates who vary across several different traits is but one potential use of CA. This technique can also be used to explore preferences for feature variations that relate to a single construct.

Specifically, CA can investigate how several traits that contribute toward a single construct impact rater's perceptions of that construct.

### Current Study

The present study contributes to current face perception literature by using CA to assess the relative contributions of several facial shape cues to perceptions of romantic partner attractiveness and masculinity. Previous research (e.g., Scheib et al., 1999; Penton-Voak et al., 2001; Koehler et al., 2004; Thornhill and Gangestad, 2006; Apicella et al., 2008) has identified several prominent shape cues that contribute to perceptions of sexual dimorphism (i.e., features that differ statistically between male and female faces): eyebrow prominence, cheekbone prominence, eye size, facial height, and jawbone prominence. Among these features, eyebrow prominence, facial height, and jawbone prominence are all reliably larger in men (i.e., are positively related to a masculine face shape and negatively related to a feminine face shape), whereas cheekbone prominence and eye size were reliably larger in women (i.e., are positively related to a feminine face shape and negatively related to a masculine face shape). Identification of the specific features that impact the overall measured sexual dimorphism of a particular individual is important for perceptual research, but no research to date has investigated how these individual features are prioritized relative to one another with respect to mate choice or with respect to the overall evaluation of a person's masculinity/femininity.

This study assessed whether individuals prioritize certain sexually dimorphic facial cues of partner quality (i.e., eyebrow prominence, cheekbone prominence, eye size, facial height, and jawbone prominence) when evaluating the attractiveness of same- and opposite-sex individuals' facial photographs as longand short-term romantic partners. Furthermore, it investigated whether individuals prioritize any of these specific features when ranking different versions of the same individual by perceived masculinity. Given that face perception is, in part, due to part-based information processing (Schwaninger et al., 2004; McKone and Yovel, 2009), it is possible that the partworth value of some facial features is weighted more heavily compared to others during partner perception. Similarly, some features may be more salient than others within different mating contexts (e.g., long- versus short-term; Buss and Schmitt, 1993; Gangestad and Simpson, 2000). Examining how these features are prioritized within long- (i.e., committed) versus short-term (i.e., purely sexual) mating contexts may explain the specific signal value of the distinct facial shape cues that contribute to person perception, and thereby reveal which features are most important to perceptions of attractive facial cues (e.g., Thornhill and Gangestad, 1999; Gangestad and Scheyd, 2005; Puts, 2010). Indeed, developing techniques that improve the accuracy of models that estimate psychological and physiological qualities from facial information (see Hu et al., 2017; Todorov, 2017) is a critical future direction in face perception research (see Jack and Schyns, 2017, for a review). Moreover, because this is the first study to manipulate individual features rather than whole faces by masculinity and femininity, the contribution of each manipulation to perceptions of facial masculinity will reveal interesting information about how we process this trait, as well as serve to further verify the computer graphics manipulations. Finally, this study will expand prior findings that used CA to study face perception (Mogilski and Welling, 2017). Because this study found that sexually dimorphic shape cues were more important than color and symmetry cues (Cohen's d ∼0.60), this study sought to examine which shape features were driving this effect. That is, this study examines whether some shape features signal relatively more information about partner quality (i.e., attractiveness; masculinity/femininity) than others.

## MATERIALS AND METHODS

### Participants

Participants (N = 922, 250 male; age: M = 20.22 years, SD = 3.53; range = 18–51) were recruited from a university in the midwestern United States and various social media outlets (e.g., Facebook, Reddit, Twitter). The majority of participants were White (78.4%; Black 9.5%, Asian 5.5%, Hispanic/Latino 2.3%, "Other" 4.3%), roughly half reported currently being single (49% versus 51% reported being in a romantic relationship), and the majority reported being exclusively heterosexual (91.3%; 6.5% bisexual, 2.2% exclusively homosexual).

## Stimuli

Using well-established methods (e.g., Jones et al., 2005; Little et al., 2007; Welling et al., 2008), composite male and female faces were generated by averaging the shape, color, and texture of a group of 60 Caucasian adult male faces and a group of 60 Caucasian adult female faces. Each composite served as the base image for a set of 19 photographs that varied exclusively by a series of objective, composite-based image transformations (detailed below). Up to five distinct facial characteristics were transformed per photograph variation: eyebrow prominence, cheekbone prominence, eye size, facial height, and jawbone prominence. These features are sexually dimorphic and vary with perceptions of facial attractiveness (Keating, 1985; Scheib et al., 1999; Penton-Voak et al., 2001; Baudouin and Tiberghien, 2004). To permit CA of participants' photograph rankings, each of the 19 photograph variations were planned using an orthogonal array generated with IBM SPSS 21, which is constructed according to a standard formula drawn from statistical reference material. A fractional-factorial design was used to minimize the number of photograph variations that participants were required to rank (Hair et al., 1995). This design generates the fewest number of profiles needed to estimate the contribution of each of the five facial characteristics to overall face evaluation. Each of the five facial features were assigned three possible levels (i.e., feature masculinization, unaltered, or feature feminization), indicating which transformations would be applied to each photograph. This produced an orthogonal array of 16 photograph variations, whereby each variation possessed a unique combination of the five facial characteristics. For example, a face might have masculinized eyebrow prominence, feminized cheekbone prominence, unaltered eye size, feminized facial

height, and masculine jawbone prominence. Three additional holdout images (for a total of 19 photographs) were included to test the validity of the CA utility estimates (see Hair et al., 1995; utility estimates and holdout profiles are defined in more detail in the Results section below). All participants ranked the same 19 images constructed based on the orthogonal array.

To alter specific facial features, image transformation methods used in prior work (e.g., DeBruine et al., 2006; Welling et al., 2007, Welling et al., 2008) were adapted to target individual features rather than whole faces. Specifically, rather than apply compositebased transformations holistically to base images (i.e., to the whole face), 5 male and 5 female composite images were first created, whereby each composite image possessed one feature (i.e., eyebrow prominence, cheekbone prominence, eye size, facial height, or jawbone prominence) of the opposite-sex, but that was otherwise sex-typical. Thus, for each composite image, the points that correspond to individual features (e.g., eye size) were altered such that they matched the position of those same points on the opposite-sex composite (see **Figure 1** for an example). These composite images were then applied to same-sex base images by taking 50% of the linear differences in 2D shape between the applicable altered composites (e.g., **Figure 1**, image C) and the original same-sex composites (i.e., **Figure 1**, image A for women, image B for men) and adding to or subtracting from corresponding points on the base image. **Figures 2**, **3** demonstrate the complete array of masculine and feminine manipulations individually applied to base female (**Figure 2**) and male (**Figure 3**) composite faces. These transformations were then applied to base images (i.e., the original, unaltered composite images) according to the orthogonal array (see **Table 1**). In other words, facial features were manipulated as per previous research (e.g., Welling et al., 2007, Welling et al., 2008) except that individual features were independently manipulated and then concurrently applied to the same face (see examples in **Figure 4**). Although no study has manipulated individual facial features in this way, holistic facial manipulations using these techniques have been shown to influence perceptions of masculinity and femininity in the predicted directions (DeBruine et al., 2006; Welling et al., 2007).

### Procedure

All experimental materials were presented using Qualtrics.  For each task, participants were presented with each of two sets (one male, one female) of nineteen digital facial photographs. Participants were asked to rank the images within each set relative to one another twice: once according to their preference for a long-term relationship and once according to their preference for a short-term relationship. Long- and shortterm relationships were defined for participants as follows:

Long-term relationship: You are looking for the type of person who would be attractive in a long-term relationship. Examples of this type of relationship would include someone you may want to move in with, someone you may consider leaving a current partner to be with, and someone you may, at some point, wish to marry (or enter into a relationship on similar grounds as marriage).

Short-term relationship: You are looking for the type of person who would be attractive in a short-term relationship. This implies that the relationship may not last a long time. Examples of this type of relationship would include a single date accepted on the spur of the moment, an affair within a long-term relationship, and the possibility of a one-night stand.

Participants were instructed to rank same-sex photographs according to how they believed a heterosexual person of the opposite-sex would rank them. The order in which the face ranking tasks and photographs within sets were presented was randomized.

## RESULTS

CA was performed to assess the relative importance of each of the five facial features in participants' ranking decisions. CA produces importance values, which indicate a feature's overall contribution to how profiles are ranked (e.g., the overall importance of cheekbone prominence, eye size, etc.), and part-worth utility estimates, which indicate the relative importance of each level within each trait (i.e., masculinization, feminization, unaltered). In other words, importance values reveal which features are weighted most heavily relative to others during ranking decisions, but not the direction of preference within any given feature (e.g., whether eyebrow prominence is more important for ratings of attractiveness than cheekbone prominence, but not whether masculine, unaltered, or feminine eyebrow prominence is preferred). On the other hand, utility estimates reveal the importance of the manipulation within a trait (e.g., preference for masculine, unaltered, versus feminine eyebrow prominence). Importance values and part-worth utility estimates were calculated for each set of faces.

Participants' rankings of holdout profiles were accurately predicted by the utility estimates (all τ = 1.00) for both

composite image. To create a male composite with feminine eye size, all points within the red square in (B) were altered to match corresponding points in (A). (C) Is a male composite with feminine eye size [i.e., all points within the red squares match (A) (female composite), whereas all points outside the red squares match (B) (male composite)].

Feminized features are presented in the top row and masculinized features are presented in the bottom row.

FIGURE 3 | Examples of each independent feature manipulation applied to the male base composite image. Feature manipulations are organized into columns. Feminized features are presented in the top row and masculinized features are presented in the bottom row.

attractiveness and masculinity assessments. Holdout profiles are image variations with unique facial characteristic combinations that are ranked alongside the original 16 profile, but which are not used to generate importance values or utility estimates. The attractiveness or masculinity of a holdout profile can be calculated using the model generated from

TABLE 1 | Orthogonal array of facial transformations and the respective image variations to which they were applied.

The number listed in the "Image variation" column corresponds to each image's numerical label in Figure 4.

participants' rankings of the other 16 images. That is, the utility estimates for each characteristic (e.g., masculinized face height, feminized eye size, etc.) can be summed within each image variation to give an overall estimated attractiveness or masculinity score for that image. How well the score for each holdout profile predicts participants' rankings of those profiles relative to each of the other 16 profiles is represented by the tau coefficient. In other words, tau represents of how well the utility estimates predict participants' rankings of the holdout profiles relative to the other 16 profiles.

For each of the following analyses, participant gender was included as an additional variable. All interactions with gender were nonsignificant even before Bonferroni correction (adjusted critical p = 0.01; all ps > 0.08). Therefore, participant gender was excluded from our report below.

### Attractiveness Ratings

#### Importance Values

looseness2 A 2(sex of face [male, female]) × 2(relationship context [long-term, short-term]) × 5(facial attribute [eyebrow thickness, cheekbone prominence, eye size, face height, jawbone prominence]) repeated-measures ANOVA was used to examine differences in importance values for each facial attribute in male and female faces ranked for desirability as long- and shortterm mates. All post hoc analyses and pairwise comparisons were adjusted using Bonferroni correction (critical p = 0.01). There was a main effect for facial attribute, F(4, 3684) = 23.41, p < 0.001, η 2 = 0.03. Importance values for eyebrow thickness (M = 21.28, SD = 6.62) were not significantly different from face height (M = 20.31, SD = 7.61, p = 0.114) or jawbone prominence (M = 20.48, SD = 5.66, p = 0.155), but both eyebrow thickness and jawbone prominence were greater than cheekbone prominence (M = 18.43, SD = 4.42, p < 0.001, d = 0.31, d = 0.29) and eye size (M = 19.49, SD = 5.36, p < 0.001, d = 0.19, d = 0.12) when ranking faces for attractiveness. Likewise, importance values were greater for face height than for cheekbone prominence (p < 0.001, d = 0.19).

 Importance values for eye size were greater for male faces (M = 20.09, SD = 7.28) than for female faces (M = 18.90, SD = 7.12), t(921) = 3.76, p < 0.001, d = 0.12, whereas importance values for face height were greater for female faces (M = 20.90, SD = 9.98) than for male faces (M = 19.73, SD = 8.36), t(921) = 3.45, p = 0.001, d = 0.12. There was also a significant interaction between relationship context and facial attribute, F(4, 3684) = 2.39, p = 0.049, η 2 = 0.003. Importance values for eyebrow thickness were greater for a long-term (M = 21.71, SD = 8.26) compared to short-term (M = 20.95, SD = 8.17) relationship context, however, this was not significant after Bonferroni correction, t(921) = 2.04, p = 0.042, d = 0.08.

#### Utility Estimates

Five 2(sex of face [male, female]) × 2(relationship context [longterm, short-term]) × 3(attribute level [masculinized, unaltered, feminized]) repeated-measures ANOVAs were used to examine differences in utility estimates for each level of each facial attribute in male and female faces ranked for desirability as long- and short-term mates. All post hoc analyses and pairwise comparisons were adjusted using Bonferroni correction (critical p = 0.017).

FIGURE 4 | Examples of composite male (top) and female (bottom) images to which one or more of the five digital transformations were applied according to an orthogonal array (see Table 1). Numerical labels correspond to the "Imagine Variation" number listed in Table 1. Base composite images were borrowed from previous work (e.g., Perrett et al., 1998; Penton-Voak et al., 1999; Jones et al., 2005; Welling et al., 2007).

#### **Eyebrow thickness**

There was a main effect for attribute level, F(2, 1842) = 27.37, p < 0.001, η 2 = 0.03. Utility estimates were greater for masculinized (M = 0.25, SD = 0.95) than for unaltered (M = −0.12, SD = 1.03, p < 0.001, d = 0.23) and feminized (M = −0.13, SD = 1.13, p < 0.001, d = 0.21) eyebrow thickness.  Utility estimates for masculinized eyebrow thickness were greater for women (M = 0.33, SD = 1.35) than for men (M = 0.17, SD = 1.19), t(921) = 2.85, p = 0.004, d = 0.10. This was further moderated by a three-way interaction, F(2, 1842) = 3.14, p = 0.044, η 2 = 0.003. For female faces, utility estimates for masculinized eyebrows were higher in a long- (M = 0.42, SD = 1.75) versus short-term (M = 0.25, SD = 1.68) context, t(921) = 2.39, p = 0.017, d = 0.11, though this was only marginally significant after Bonferroni correction. There were no other significant main effects or interactions (all F < 1.96, all p > 0.141).

#### **Cheekbone prominence**

There was a main effect for attribute level, F(2, 1842) = 30.63, p < 0.001, η 2 = 0.03. Utility estimates were greater for masculinized (M = 0.21, SD = 0.79) than unaltered (M = −0.11, SD = 0.78, p < 0.001, d = 0.25) and feminized (M = −0.11, SD = 0.90, p < 0.001, d = 0.21) cheekbones. There were no other significant main effects or interactions (all F < 2.09, all p > 0.124).

#### **Eye size**

There was a main effect for attribute level, F(2, 1842) = 58.21, p < 0.001, η 2 = 0.06. Utility estimates were higher for unaltered (M = 0.23, SD = 0.78) than masculinized (M = 0.09, SD = 0.91, p = 0.006, d = 0.11) and feminized (M = −0.32, SD = 1.07, p < 0.001, d = 0.30) eye size. Estimates were also higher for masculinized compared to feminized eye size (p < 0.001, d = 0.25). There was also a significant interaction between relationship context and attribute level, F(2, 1842) = 3.37, p = 0.035, η 2 = 0.004. Utility estimates for masculinized eye size were greater in a short- (M = 0.15, SD = 1.04) versus long-term (M = 0.04, SD = 1.05) context, t(921) = −2.37, p = 0.018, d = 0.08, whereas unaltered eye size was preferred in a long- (M = 0.29, SD = 1.21) compared to short-term (M = 0.16, SD = 1.24) context, t(921) = 2.33, p = 0.020, d = 0.01, however, both were nonsignificant after Bonferroni correction. There were no other significant main effects or interactions (all F < 2.18, all p > 0.113).

#### **Face height**

There was a main effect for attribute level, F(2, 1842) = 26.88, p < 0.001, η 2 = 0.03. Utility estimates were greater for unaltered (M = 0.24, SD = 1.07) versus masculinized (M = −0.10, SD = 0.84, p < 0.001, d = 0.21) and feminized (M = −0.14, SD = 1.06, p < 0.001, d = 0.24) face height.  Utility estimates for masculinized face height were greater for male (M = 0.25, SD = 1.65) than female (M = −0.45, SD = 1.65) faces, t(921) = 9.71, p < 0.001, d = 0.30. Likewise, estimates for feminized face height were lower for male (M = −0.43, SD = 1.45) than female (M = 0.15, SD = 1.50) faces, t(921) = −8.60, p < 0.001, d = 0.29. There were no other significant main effects or interactions (all F < 1.24, p > 0.290).

#### **Jawbone prominence**

There was a main effect for attribute level, F(2, 1842) = 101.85, p < 0.001, η 2 = 0.10. Utility estimates were greater for masculinized (M = 0.26, SD = 0.88, p < 0.001, d = 0.40) and feminized (M = 0.17, SD = 0.84, p < 0.001, d = 0.36) compared to unaltered (M = −0.43, SD = 1.02) jawbone prominence.  Utility estimates for masculinized jawbone prominence were greater for male (M = 0.36, SD = 1.15) than for female (M = 0.16, SD = 1.12) faces, t(921) = 4.19, p < 0.001, d = 0.14, whereas estimates for feminized jawbone prominence were greater for female (M = 0.28, SD = 1.19) than for male (M = 0.06, SD = 1.21) faces, t(921) = −3.88, p < 0.001, d = 0.13. There were no other significant main effects or interactions (all F < 1.30, all p > 0.273).

## Masculinity Ratings

fpsyg-09-02428 December 3, 2018 Time: 11:4 # 8

#### Importance Values

A 2(sex of face [male, female]) × 5(facial attribute [eyebrow thickness, cheekbone prominence, eye size, face height, jawbone prominence]) repeated-measures ANOVA was used to examine differences in importance values for each facial attribute in male and female faces ranked for masculinity. There was a main effect for facial attribute, F(4, 3684) = 17.61, p < 0.001, η 2 = 0.02. Importance values for eyebrow thickness (M = 21.09, SD = 8.65), face height (M = 21.13, SD = 10.23), and jawbone prominence (M = 20.38, SD = 7.49) were not significantly different, but each was significantly greater than cheekbone prominence (M = 18.34, SD = 6.47; d = 0.23; d = 0.21; d = 0.21, respectively) and eye size (M = 19.07, SD = 6.98; d = 0.16; d = 0.15; d = 0.11, respectively) (all ps < 0.001).  Importance values for face height were greater for female (M = 22.09, SD = 13.18) than for male (M = 20.17, SD = 11.76) faces, t(921) = 4.06, p < 0.001, d = 0.14. By contrast, importance values for jawbone prominence were greater for male (M = 20.90, SD = 9.74) than for female (M = 19.86, SD = 10.21) faces, though this difference was only marginally significant after Bonferroni correction, t(921) = 2.39, p = 0.017, d = 0.08.

#### Utility Estimates

Five 2(sex of face [male, female]) × 3(attribute level [masculinized, unaltered, feminized]) repeated-measures ANOVAs were used to examine differences in utility estimates for each level of each facial attribute in male and female faces ranked for perceived masculinity.

#### **Eyebrow thickness**

There was a main effect for attribute level, F(2, 1842) = 77.97, p < 0.001, η 2 = 0.08. Utility estimates were greater for masculinized (M = 0.43, SD = 1.29) than unaltered (M = 0.08, SD = 1.26, p < 0.001, d = 0.17) and feminized (M = −0.51, SD = 1.46, p < 0.001, d = 0.39) eyebrow thickness. There were no other significant main effects or interactions (all F < 0.88, all p > 0.417).

#### **Cheekbone prominence**

There was a main effect for attribute level, F(2, 1842) = 10.73, p < 0.001, η 2 = 0.01. Utility estimates were greater for masculinized (M = 0.17, SD = 1.09) than for feminized (M = −0.07, SD = 1.19, p = 0.001, d = 0.09) and unaltered (M = −0.11, SD = 1.10, p < 0.001, d = 0.11) cheekbone prominence. There was also a significant interaction between sex of face and attribute level, F(2, 1842) = 3.17, p = 0.042, η 2 = 0.003. Utility estimates for feminized cheekbone prominence were greater for female (M = 0.02, SD = 1.64) than for male (M = −0.15, SD = 1.64) faces, though this was only marginally significant after Bonferroni correction, t(921) = 2.34, p = 0.019, d = 0.08.

#### **Eye size**

There was a main effect for attribute level, F(2, 1842) = 29.53, p < 0.001, η 2 = 0.03. Utility estimates were greater for masculinized (M = 0.26, SD = 1.02) than for unaltered (M = 0.00, SD = 1.23, p < 0.001, d = 0.15) and feminized (M = −0.26, SD = 1.32, p < 0.001, d = 0.25) eye size. Estimates were also greater for unaltered than for feminized eye size (p = 0.002, d = 0.11). There were was no other significant main effects or interactions (all F < 0.91, p > 0.401).

#### **Face height**

There was a main effect for attribute level, F(2, 1842) = 147.61, p < 0.001. η 2 = 0.14. Utility estimates were greater for masculinized (M = 0.72, SD = 1.57) than for unaltered (M = −0.05, SD = 1.12, p < 0.001, d = 0.34) and feminized (M = −0.66, SD = 1.49, p < 0.001, d = 0.49) face height. Similarly, estimates were greater for unaltered compared to feminized face height (p < 0.001, d = 0.28). There was also a significant interaction between sex of face and attribute level, F(2, 1842) = 3.10, p = 0.045, η 2 = 0.003. Utility estimates for masculinized face height were greater for female (M = 0.81, SD = 2.14) than for male (M = 0.63, SD = 1.78) faces, t(921) = −2.30, p = 0.022, d = 0.08, whereas estimates for unaltered face height were greater for male (M = 0.02, SD = 1.49) than for female (M = −0.13, SD = 1.55) faces, t(921) = 2.09, p = 0.037, d = 0.07. However, both of these pairwise comparisons were nonsignificant after Bonferroni correction.

#### **Jawbone prominence**

There was a main effect for attribute level, F(2, 1842) = 44.30, p < 0.001, η 2 = 0.05. Utility estimates were greater for masculinized (M = 0.35, SD = 1.15) than for unaltered (M = −0.31, SD = 1.32, p < 0.001, d = 0.30) and feminized (M = −0.04, SD = 1.23, p < 0.001, d = 0.20) jawbone prominence. Estimates were also higher for feminized than for unaltered jawbone prominence (p < 0.001, d = 0.12). There were no other significant main effects or interactions (all F < 1.14, p > 0.321).

## DISCUSSION

The relative importance of five facial features (i.e., eyebrow thickness, cheekbone prominence, eye size, face height, and jawbone prominence) to perceptions of physical attractiveness and masculinity were assessed during participants' evaluations of potential romantic partners' facial photographs. CA was used to calculate individual facial feature importance values in overall rankings of attractiveness and masculinity and utility estimates for each attribute. Importance values for perceived masculinity were not significantly different for eyebrow thickness, face height, or jawbone prominence, but each of these traits was significantly greater than cheekbone prominence and eye size, suggesting that perceptions of physical masculinity are more strongly influences by eyebrow thickness, face height, and jawbone prominence

compared to cheekbone prominence and eye size.  This indicates that a masculinized face height has a greater impact on the perceived masculinity of women's faces than men's faces. The opposite was true of jawbone prominence, which was perceptually more important in attributing masculinity to male faces than female faces. This latter finding should be interpreted with caution, however, as the effect fell short of significance after Bonferroni correction. Finally, utility estimates for masculinity rankings indicated that all features manipulated to appear more masculine or more feminine were ranked as such. Importantly, this indicates that the transformations were perceived as intended, further validating the use of computer graphics methods in objectively manipulating perceptions of sexual dimorphism (see also, e.g., Welling et al., 2007).

For physical attractiveness, these estimates were compared across (1) long- and short-term relationship contexts, and (2) sex of the face. With respect to physical attractiveness importance values, eyebrow thickness was not significantly more important than face height or jawbone prominence, but both eyebrow thickness and jawbone prominence were more important than cheekbone prominence and eye size when ranking faces for attractiveness. Likewise, importance values were greater for face height than for cheekbone prominence. In other words, participants in the current sample weighted the appearance of eyebrow thickness, face height, and jawbone prominence as most important in determining overall attractiveness, and eyebrow thickness and jawbone prominence as more important than eye size. Each of these traits appear to be important during zero-acquaintance assessments of physical attractiveness (Cunningham, 1986; Baudouin and Tiberghien, 2004), social dominance and maturity (Keating, 1985; Cunningham et al., 1990), and personality (Paunonen et al., 1999), however, this was the first study to examine which features are relatively more salient when digitally altered and presented alongside other digitally altered facial features within the same facial identity. Furthermore, no study has isolated the precise informational value of each particular facial feature to overall potential partner assessment. In this sense, it is difficult to conclude precisely why certain features were prioritized over others, although it opens up promising avenues for future investigation. Therefore, the informational value of each trait to perceptions of attractiveness may be best interpreted with respect to how preference for these traits varies across relationship context and sex of the face.

Importance values revealed that eye size was relatively more important for male versus female faces. Specifically, utility estimates showed that unaltered eye size was preferred more than masculinized or feminized eye size, and masculinized eye size was preferred more than feminized eye size, when collapsing across sex of face. However, masculinized (i.e., smaller) eye size was preferred more within short- versus long-term relationship contexts. One possibility is that eye size is an important attractiveness indicator in men insofar as individuals with smaller (i.e., masculinized) eyes are perceived as more mature or more socially dominant (Keating, 1985), which may make them more desirable as potential sexual (but not necessarily long-term) partners. Interestingly, unaltered eye size was preferred more in a long- compared to short-term context, perhaps suggesting that only a moderate level of masculinity/femininity is preferred in a long-term mate. However, these latter two findings fell short of significance after Bonferroni correction and should be interpreted with caution.

Importance values for face height were greater for female faces than for male faces, suggesting that the overall signal value of face height is more valuable for attributions of female attractiveness than for attributions of male attractiveness. Utility estimates revealed that masculinized face height was considered more attractive for male versus female faces, and, correspondingly, that feminized face height was preferred less for male versus female faces. Thus, sex-typical face height is preferred in both sexes, but the value of this trait in general is more salient in women's faces compared to men's, likely reflecting greater preferences for sex-typical women versus men (see Little et al., 2014). Similarly, utility estimates for masculinized jawbone prominence were greater for male than for female faces, and, correspondingly, estimates for feminized jawbone prominence were greater for female than for male faces, again suggesting that sex-typical traits are preferred more than sex-atypical traits. However, utility estimates were greater for masculinized compared to unaltered and feminized cheekbone prominence, regardless of the sex of the faces being ranked. Although sensible for male faces, this finding is unexpected for female faces, among whom one would expect a higher preference for feminized (i.e., more prominent) cheekbones. It is possible that participants simply preferred more masculine cheekbone prominence in both sexes, but this interpretation should be taken with caution because the highly subtle nature of this particular manipulation may have also made the differences more difficult to discern for the participants. That said, participants did accurately perceive masculinized cheekbone prominence as more masculine than unaltered or feminized cheekbone prominence, suggesting the manipulation was not imperceptibly subtle. This relationship should be investigated more thoroughly in future work.

Finally, although importance values for eyebrow thickness were greater for a long-term compared to short-term relationship context, this relationship was not significant after Bonferroni correction. Surprisingly, utility estimates revealed that thicker eyebrows were more attractive for female faces than male faces, particularly within a long-term mating context. Previous research shows that thicker eyebrows are typically perceived as more masculine and dominant (Windhager et al., 2011) and are more attractive in male than female faces (Keating, 1985), making this finding unexpected. It is possible that unmeasured personality features (e.g., sociosexuality, self-rated attractiveness) of the raters may moderate these findings. Indeed, recent work suggests that eyebrows may signal personality qualities (e.g., narcissism; Giacomin and Rule, 2018) that influence perceptions of attractiveness. Additionally, effect sizes in the current study were relatively small, and so investigation into the mediating effects of individual difference variables may further explain this relationship. Alternatively, it is possible that current and/or

temporary cosmetic and style trends popular among the tested cohort are influencing this relationship, and so this relationship may not generalize to other populations. Certainly, this requires further investigation.

## CONCLUSION