Evidence that the presence of others may change our own coding of spatial locations of objects is provided by recent studies investigating spatial judgment (Tversky and Hard, 2009; Zwickel, 2009; Zwickel and Müller, 2010). In a typical experiment, participants viewed a photograph of two objects on a table. When participants were asked to describe the location of one object relative to another, the dominant response was to adopt their own spatial perspective. If, however, the scene included a person looking or reaching for one of the objects, almost one third of participants spontaneously adopted the other person's perspective, describing the locations from the other's right or left (Tversky and Hard, 2009). These findings indicate that the presence of another person may encourage participants to spontaneously take that person spatial perspective, and describe the locations of the objects from her right or left. Similarly, studies investigating spontaneous visual perspective taking found that observers were slower to make self-perspective judgments when the scene includes a person looking at the scene from a different visual perspective, suggesting that even when the other person's perspective is irrelevant to the task, observers cannot prevent computing the other's perspective (Samson et al., 2010).

What makes people spontaneously take others' perspectives despite the very real presence of their own? The "mere presence" of a human body does not seem sufficient to elicit spontaneous perspective taking (Mazzarella et al., 2012). People adopt the perspective of another person who acts (Frischen et al., 2009; Thirioux et al., 2010) or is positioned to act on objects and even more so when attention is drawn to the person's potential for action, for instance, by phrasing the query about spatial relations in terms of action (e.g., "In relation to the bottle, where does he place the book?" Tversky and Hard, 2009). What is more, people even adopt the perspective of simple geometric shapes when the actions of the shapes appear intentional (Zwickel, 2009).

Together, the research suggests that spontaneous perspective taking may be related to understanding and anticipating another's action rather than to the mere presence of a human body. If so, perspective taking should increase when the perceived intention to act increases. This prediction was tested in the first of two experiments. Participants were presented with brief videos (rather than still photographs) depicting two objects, a milk cartoon and a glass full of milk, on a table, with or without a person behind (see **Figure 1**). Because looking at an object often signals intention to act on the object (Allison et al., 2000; Mennie et al., 2007; Becchio et al., 2008; Pierno et al., 2008; Sartori et al., 2009; Innocenti et al., 2012), the tendency to take the actor's perspective should be stronger when the actor looks at one of the objects and even stronger when the actor reaches toward the object.

Findings concerning the contribution of gaze cues to spontaneous perspective taking have not been consistent. Using static photographs, Tversky and Hard (2009) found no significant difference in the proportion of description from the other's point of view for looking and looking-and-reaching scenes, suggesting that gaze shifts and overt hand actions have similar effects on perspective taking. In contrast, however, Mazzarella et al. (2012) found that the actor's hand action, but not the actor's gaze,

modulated the tendency to adopt his perspective. The question remains therefore open as to whether gaze contributes to perspective taking. To address this issue, in a second experiment we manipulated the congruency of gaze and action cues. Gaze cues can be informative but also produce ambiguity with respect to others' actions and behavioral intentions. For instance, football and basketball players often "fake" to fool their opponents, by looking in one direction and acting in another. We predicted that if perspective taking is related to understanding another's action, then, by making the agent's intention ambiguous, incongruous gaze would increase perspective taking.

#### **STUDY 1: SPONTANEOUS PERSPECTIVE TAKING INCREASES AS PERCEIVED INTENTIONALITY INCREASES**

Study 1 was designed to test whether the perceived potential for interaction with objects increases spontaneous perspective taking. We predicted that the more a person is perceived as potentially acting on an object, the greater the need to understand the action, hence in the scene, the stronger the tendency to spatially represent the locations of the objects from the actor's perspective.

#### **METHODS**

#### *Participants*

One hundred and twenty undergraduate students (53 male and 67 female; mean age: 23.5 ± 3.3, range 18–37 years) from the University of Turin volunteered to take part in the experiment. All had normal or corrected-to-normal vision, were right handed, and were naïve with respect to the purpose of the study.

#### *Materials and procedures*

Participants were presented with one of four videos depicting two objects, a milk cartoon and a glass full of milk, on a table. Scene information was manipulated by introducing an actor model and by varying the actor's gaze and action (see **Figure 1**). In the *No Actor* video (*n* = 30) no actor model was present. The other three videos included an actor. The *Actor* video (*n* = 30) showed the actor stationary, looking down, seemingly unaware of the objects on the table. In the *Gaze* video (*n* = 30) the actor turned his head to look toward the glass, but did not reach it. In the *Gaze Action* video (*n* = 30) the actor turned the head to look toward and reached for the glass. Videos including the actor started with the actor looking down for 2 s. The actor then turned his head to look at the object (in the *Gaze* and the *Gaze Action* video) and, after 1 s, reached for the object (in the *Gaze Action* video). Each video lasted 4.15 s. The question "In relation to the glass, where

is the milk cartoon?" was displayed below the last frame of each video and remained visible until response or until 9 s elapsed. Participants' verbal responses were recorded by the experimenter who was sitting behind the participant.

#### **DATA ANALYSIS AND RESULTS**

The responses were scored as 1PP (first person perspective) if the answer was from the participant's point of view, 3PP (third person perspective) if the answer was from the actor's viewpoint, and neutral if the answer gave spatial information from neither perspective (e.g., "next to," "to the side," "on the table"). Examples of responses scored as 1PP include: "right," "on the right," "to the right from my perspective." Examples of responses scored as 3PP include: "left," "to his left," "to the left from his perspective." Scored responses were converted into three binary variables for analysis: one variable was coded 1 if the response was 3PP and 0 if it was not; the second variable was coded 1 if the response was 1PP and 0 if it was not; the third variable was coded 1 if the response was neutral and 0 if it was not. To assess the influence of agency cues on spontaneous perspective taking, separate binary logistic regression analyses were conducted on 3PP, 1PP, and neutral responses. The type of video (*No Actor, Actor, Gaze, Gaze Action*) was entered as independent variable of interest.

In line with predictions, binary logistic regression analysis on 3PP responses yielded a significant linear effect of agency (Wald χ2 = 10.903, *df* = 1, odd ratio = 1.968, CI = 1.317–2.941, *p* = 0.001). The percentage of 3PP responses was highest for *Gaze Action* video (43.3%), lower for the *Gaze* video (36.7%), and even lower for the *Actor* video (30%, see **Figure 2**). For the *No actor* video, only one participant adopted the 3PP perspective. Similarly, the percentage of 1PP responses was affected by agency cues (Wald χ2 = 7.872, *df* = 1, odd ratio = 0.591, CI = 0.409– 0.853, *p* = 0.005). The percentage of 1PP responses was highest for the *No Actor* video (90%), lower for the *Actor* video (63.3%) and the *Gaze* (63.3%) video, and lowest for the *Gaze Action* video (53.3%, see **Figure 2**). The percentage of neutral responses was not affected by agency cues (Wald χ2 = 0.993, odd ratio = 0.645, CI = 0.272–1.528, *p* = 0.319).

Together, these findings corroborate and extend the idea that increased potential for interaction enhances spontaneous perspective taking.

#### **STUDY 2: SPONTANEOUS PERSPECTIVE TAKING INCREASES AS INCONGRUITY OF INTENTION INCREASES**

Gaze is an important source of information about others' intentions and actions (Allison et al., 2000; Mennie et al., 2007; Becchio et al., 2008; Pierno et al., 2008; Sartori et al., 2009; Innocenti et al., 2012). From the gaze of another person, we can infer what the person is interested in, what she might desire, and, consequently, what she will do next (Pierno et al., 2006). Gaze direction, however, can also produce ambiguity with respect to the other's intention. This can occur, when gaze conveys conflicting information with respect to the behavioral intention of the agent (Hudson and Jellema, 2011). In this situation, the agent's action can be perceived as ambiguous and observers might be encouraged to adopt the perspective of the other person to understand her intention. Spontaneous perspective taking might thus be expected to be even stronger when gaze is incongruous than when gaze and action signal the same, and therefore unambiguous, intention.

To test this prediction, in Study 2, we presented participants with videos of an actor reaching for a glass in presence of a milk cartoon. The actor either looked toward the glass before reaching (*Gaze Action*) or reached without looking (*Ambiguous Gaze Action*). We predicted that the absence of a shift of gaze in the direction of action would make the action harder to understand and therefore increase the likelihood of adopting the actor perspective. In contrast, no increase in perspective taking should be expected when access to the actor's gaze during reaching is prevented by blurring the actor's face (*Blurred Gaze Action*). This is because, in this situation, the absence of gaze cues does not render the agent's behavioral intention ambiguous.

## **METHODS**

#### *Participants*

Based on the prevalence of 3PP/1PP responses for the *Gaze Action* scene compared to the *Actor* scene and the *Gaze* scene in Experiment 1 (9.7%), we estimated that we would need 135 participants in each condition to evaluate the effect of gaze manipulations on 3PP and 1PP responses (see Supplementary Material). Four hundred and five undergraduate students (191 male and 214 female; mean age: 23.3 ± 3.3; range 18–48 years) from the University of Turin were thus recruited to take part in Experiment 2. All had normal or corrected-to-normal vision, were right handed, and were naïve with respect to the purpose of the study.

#### *Materials and procedures*

Procedures were the same as those in Study 1, except that participants were presented with one of three videos depicting an actor reaching for one of two objects—a milk cartoon and a glass full of milk—on a table (see **Figure 3**). In the *Gaze Action* video (*n* = 135) the actor turned his head, looked toward and reached for the glass (see Study 1). In the *Blurred Gaze Action* video (*n* = 135) the actor turned his head, looked toward and reached for the glass as in the *Gaze Action* video. Access to the actor's gaze direction was, however, prevented by blurring the actor's face. In the *Ambiguous Gaze Action* video (*n* = 135) the actor reached for the glass without looking at it.

**FIGURE 3 | Final frames for videos in Experiment 2.** In the *Gaze Action* video **(A)** the actor turned the head to look toward and reached for the glass. In the *Blurred Gaze Action* video **(B)** the actor turned his head, looked toward and reached for the glass but participant's access to the actor's gaze direction was prevented by blurring the actor's face. In the *Ambiguous Gaze Action* video **(C)**, the actor reached the glass without looking toward it.

#### **DATA ANALYSIS AND RESULTS**

As in Study 1, the responses were scored as 1PP if the answer was from the participant's point of view, 3PP if the answer was from the actor's viewpoint, and neutral if the answer gave spatial information from neither perspective. Separate chi square analyses were conducted to compare observed frequencies of 3PP (vs. 1PP and neutral responses), 1PP (vs. 3PP and neutral responses), and neutral responses (vs. 1PP and 3PP responses) for the *Ambiguous Gaze Action* and for the *Blurred Gaze Action* scenes with expected frequencies for the *Gaze Action* scene.

Strikingly, when the actor reached without looking, 51.1% of the participants adopted his perspective (see **Figure 4**). Chisquare analysis revealed a marginally significant increase in 3PP responses for the *Ambiguous Gaze Action* scene compared to the *Gaze Action* scene (51.1% vs. 40.7%; χ2 = 3.713, *df* = 1, *p* = 0.054, *r* = 0.166). Conversely, 1PP responses were significantly lower for videos in which the actor reached without looking than for videos in which reaching was preceded by looking (40% vs. 52,6%; χ2 = 8.586, *df* = 1, *p* = 0.003, *r* = 0.252). Taken together, these findings suggest that perspective taking was increased for the *Ambiguous Gaze Action* scene compared to the *Gaze Action* scene. As predicted, *Blurred Gaze Action* and *Gaze Action* videos yielded equivalent percentages of 3PP (42.2% vs. 40.7%; χ2 = 0.112, *df* = 1, *p* = 0.738, *r* = 0.029) and 1PP responses (52.5% vs. 49.6%; χ2 = 2.478, *df* = 1, *p* = 0.115, *r* = 0.029). Neutral responses were neither affected by the ambiguity of actor's intentions (6.6% vs. 8.8%; χ2 = 1.071, *df* = 1, *p* = 0.301, *r* = 0.089) nor by the gaze blurring (6.6% vs. 8.1%; χ2 = 0.476, *df* = 1, *p* = 0.490, *r* = 0.059).

## **GENERAL DISCUSSION**

Converging evidence from social neuroscience suggests that people use knowledge of their own bodies to understand other people's behavior (Grafton, 2009). Accordingly, understanding of others' actions, intentions, and emotions has been proposed to rely on mechanism of embodied simulation (e.g., Becchio et al., 2012). Together with previous research (e.g., Tversky and Hard, 2009), the present results suggest that, in the service of action understanding, people may also embody others' location, spatially representing the world from others' point of view rather than from their own.

#### **AGENCY CUES IN VIDEO DISPLAYS**

The mere presence of another person in a position to act on objects encouraged about 30% of respondents to take the other person's perspective. Critically, as demonstrated in Study 1, the tendency to take the actor's perspective increased when the actor looked at one of the objects (36.7%) and became even stronger when the actor reached for one object (43.3%). This corroborates the interpretation that perspective taking increases to the extent that the person is perceived to be potentially interacting with the objects.

Previous studies investigating spontaneous perspective taking have reported considerably lower percentages of third-person responses for looking and reaching scenes then those reported here (e.g., 22 and 29%, respectively; Tversky and Hard, 2009). One aspect of the present study that is likely to have contributed to increase perspective taking is the use of videos instead of photographs. Videos provide dynamic cues to action not available in static displays. As human observers are particularly sensitive to human body movements (Blake and Shiffrar, 2007), it is plausible that the gradual unfolding of action emphasizes and draws attention to action, thereby increasing perspective taking.

A question for future research is whether perspective taking is further encouraged by the observation of actions potentially directed at the observer. Social cognition has been proposed to be substantially different when we are in interaction with others (second-person interaction) rather than merely observing them (third-person interaction; Schilbach et al., 2013). Second-person interaction modulates emphatic brain responses (Singer et al., 2006) and there is evidence that simulation of another person's action, as reflected in the activation of the observer motor system, gets stronger the more the other is perceived as an interaction partner (Kourtis et al., 2010). In terms of perspective taking, observation of the actions of a potentially interacting partner might thus be expected to elicit stronger perspective compared to observation of the actions of a third party we do not interact with.

#### **WHEN LOOKING IS AMBIGUOUS**

Mazzarella et al. (2012) reported that action triggered perspective-taking, but gaze cues did not. They suggests that this may be because eye gaze is not critically relevant, as grasping is, to understanding what an actor is currently doing. However, other research has shown that other gaze direction is informative not only about *future intentions* but also about *present intentions* and *motor intentions* and can change the way current actions are perceived (Pierno et al., 2008). Reaching is typically guided by the eyes. Gaze leads the hand to the object to be grasped and supports predictive motor control in manipulation (Johansson et al., 2001). Observing a person grasping without looking may thus be perceived as ambiguous. What is he planning to do? Why is he not looking at the object he is reaching for? In Experiment 2 we found that compared to a situation in which gaze and action signaled the same intention, perspective taking increased for reaching without looking, apparently in an effort to understand the intended action in the face of conflicting cues. In contrast, we observed no increase in perspective taking when looking cues were eliminated by blurring the eyes, suggesting that when there was no conflict, observers used the direction of reaching as a cue to understand the intention.

Allocation of attention to gaze cues is a flexible process that depends in part on the perceived ambiguity of an agent's intentions. Observers do not attend to an agent's gaze direction automatically, but rather do so when other social cues are insufficient to determine the immediate course or goal of the action (Hudson and Jellema, 2011). The present findings suggest that similarly to attention, perspective taking may not be triggered directly by the perceptual properties of gaze stimuli, but may depend on gaze intentional significance in the overall context. When gaze and action cues convey the same information, gaze processing adds little to action in terms of intention attribution. Eliminating gaze cues has thus no influence on perspective taking. However, when gaze and action convey incongruous information making the agent's intention ambiguous, gaze direction becomes relevant and may increase spontaneous perspective taking. These findings may help to reconcile inconsistent findings concerning the relative contributions of gaze and action cues to perspective taking (e.g., Tversky and Hard, 2009; Mazzarella et al., 2012) by showing that, rather than depending on specific bodily cues (and not others), perspective taking is influenced by the attribution of intentions to others.

## **CONCLUSIONS**

Here, participants watched videos of two objects on a table under varying conditions. They were asked to report the spatial relations between the two objects. When only the objects were in the scene, participants responded from their own viewpoint. However, when the scene included an actor in the position to act on the objects, participants frequently took the actor's perspective. The first study showed that the more the actor was perceived as potentially interacting with the objects, the stronger the tendency to take his perspective. The second study investigated how manipulations of gaze affect the tendency to adopt the perspective of another reaching for an object and found that perspective-taking increased when gaze and reaching information was incongruous making the agent's behavioral intention ambiguous. These findings add further support to the idea that spontaneous perspective taking is in the service of action understanding. When the action is more difficult to understand, there is more perspective taking. It is as if observers are putting themselves in the place of the actor to understand what he is intending to do.

But why would someone spontaneously take the spatial perspective of another when the other appears to be engaged in action? Interacting with others, understanding what they are doing and what they are likely to do next all require some comprehension of what the world looks like to them. As suggested previously (Tversky and Hard, 2009), taking the perspective of the other may be effective for planning a response to others' actions, but also for learning by observation. What makes the current results surprising is that the action was mundane—so no need to learn by observation—and required no complementary action in response. Even more surprising is that the perspective was expressed in language, in the especially confusable terms, "left"

#### **REFERENCES**

*Untersuchungen zur Konstitution*. The Hague: Martin Nijhoff.

and "right," which are well-known to take more time to produce and to produce more errors than other directional terms like "front" and "back." Despite this, when the agent's intention was ambiguous, the majority of participants spontaneously adopted the agent's perspective rather than their own.

#### **ACKNOWLEDGMENTS**

This work was supported by a grant from the Regione Piemonte, bando Scienze Umane e Sociali 2008, L.R. n.4/2006 to Cristina Becchio.

#### **SUPPLEMENTARY MATERIAL**

The Supplementary Material for this article can be found online at: http://www.frontiersin.org/Human\_Neuroscience/ 10.3389/fnhum.2013.00455/abstract

gaze turns into grasp. *J. Cogn. Neurosci*. 18, 2130–2137. doi: 10.1162/jocn.2<IP_ADDRESS>0

*Cognition* 110, 124–129. doi: 10.1016/j.cognition.2008.10.008

**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.

*Received: 17 May 2013; accepted: 22 July 2013; published online: 12 August 2013. Citation: Furlanetto T, Cavallo A, Manera V, Tversky B and Becchio C (2013) Through your eyes: incongruence of gaze and action increases spontaneous perspective taking. Front. Hum. Neurosci. 7:455. doi: 10.3389/fnhum. 2013.00455*

*Copyright © 2013 Furlanetto, Cavallo, Manera, Tversky and Becchio. 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) or licensor 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.*

## Psychological influences on distance estimation in a virtual reality environment

#### *Kohske Takahashi 1 \*†, Tobias Meilinger 1,2†, Katsumi Watanabe1 and Heinrich H. Bülthoff 2,3\**

*1 Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan*

*2 Department of Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Tübingen, Germany*

*3 Department of Brain and Cognitive Engineering, Korea University, Seoul, Korea*

#### *Edited by:*

*Sarah H. Creem-Regehr, University of Utah, USA*

#### *Reviewed by:*

*Sarah H. Creem-Regehr, University of Utah, USA Matthew R. Longo, Birkbeck, University of London, UK*

#### *\*Correspondence:*

*Kohske Takahashi, Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan e-mail: ktakahashi@fennel. rcast.u-tokyo.ac.jp; Heinrich H. Bülthoff, Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, 72076 Tübingen, Germany e-mail: heinrich.buelthoff@ tuebingen.mpg.de †These authors have contributed equally to this work.*

Studies of embodied perception have revealed that social, psychological, and physiological factors influence space perception. While many of these influences were observed with real or highly realistic stimuli, the present work showed that even the orientation of abstract geometric objects in a non-realistic virtual environment could influence distance perception.  Subsequently, the observers estimated the distance to the cones or evaluated their friendliness. The cones either faced the observer, a target behind the cones, or were oriented randomly. The average viewing distance to the cones varied between 1.2 and 2.0 m. At a viewing distance of 1.6 m, the observers perceived the cones facing them as closer than the cones facing a target in the opposite direction, or those oriented randomly. Furthermore, irrespective of the viewing distance, observers moved their head away from the cones more strongly and evaluated the cones as less friendly when the cones faced the observers. Similar distance estimation results were obtained with a 3-dimensional projection onto a large screen, although the effective viewing distances were farther away. These results suggest that factors other than physical distance influenced distance perception even with non-realistic geometric objects in a virtual environment. Furthermore, the distance perception modulation was accompanied by changes in subjective impression and avoidance movement. We propose that cones facing an observer are perceived as socially discomforting or threatening, and potentially violate an observer's personal space, which might influence the perceived distance of cones.

**Keywords: distance perception, spatial perception, virtual reality environment, personal space, object geometry**

## **INTRODUCTION**

Perceived space is not necessarily veridical, as demonstrated by many optical illusions (e.g., Müller-Lyer illusion, Ponzo illusion, and the Ebbinghaus illusion). Apart from illusions, spatial perception is susceptible to the influences of observer's psychological and physiological states. Hills appear steeper after a 1-h run (Proffitt et al., 1995; Proffitt, 2006), and a glass of water looks larger when observers feel thirsty (Veltkamp et al., 2008). These studies support the notion of embodied perception, according to which observers' mental and bodily states modify spatial perception (Proffitt, 2006).

Of our particular interest is distance perception. Distance modulates, explicitly and implicitly, the way we behave in the real world (e.g., personal space, Liberman et al., 2007). Recently, many studies have examined how factors other than physical distance influence distance perception. For example, desired objects are felt as nearer or are seen as closer (Balcetis and Dunning, 2010; Alter and Balcetis, 2011). Wearing a backpack or throwing a heavy ball results in larger subsequent distance estimations compared with wearing no backpack or throwing a light ball (Proffitt et al., 2003; Witt et al., 2004). Threatening objects (e.g., a living tarantula) are perceived as closer (Cole et al., 2012). A location related to a rival group (e.g., Fenway Park for a Yankees fan) is imagined as nearer when accompanied by a feeling of threat (Xiao and Van Bavel, 2012). These studies imply that distance perception reflects more than physical distance, namely, social, psychological, and physiological aspects.

Thus far, the influence of the social, psychological, or physiological factors on distance perception have been tested primarily in real world situations with semantically meaningful stimuli, in line with the notion of embodied perception (Proffitt, 2006). These situations evoke associations between the presented stimuli and expected reward or punishment (e.g., a tarantula might hurt us at a closer distance). It would be plausible to argue that the expectations of reward or punishment (i.e., prospect and threat) influence distance perception by modulating psychological states. In the present study, we simplified the situation so that visual stimuli no longer afforded realistic rewards or punishments and observers were aware that the affective values associated with the visual stimuli, if any, were not real. For this purpose, we investigated the modulation of distance perception using a virtual environment and meaningless geometric objects. A virtual environment is an experimental tool used increasingly in a wide range of contexts from navigation behavior (e.g., Frankenstein et al., 2012) to social phenomena (e.g., personal space, Bailenson et al., 2003). In virtual environments, objects are typically not real, which enables us to examine situations where observers know that the objects are *not* associated with realistic rewards or punishments (e.g., a tarantula in a virtual environment will not hurt us even at the closest distance). We presented cone-shaped objects and manipulated the orientation of the cones. The tips of the cones faced an observer, faced another location in a virtual environment, or were oriented randomly. We expected the psychological reaction to vary depending on cone orientation. In particular, the cone tips that faced the observer might induce threat or unfriendliness as in the real world situations, wherein some people develop aichmophobia, an excessive fear of sharp or pointy objects such as needles (Morse and Cohen, 1983; Shabani and Fisher, 2006).

#### **EXPERIMENT 1**

## **MATERIALS AND METHODS**

#### *Observers*

Fourteen paid volunteers (3 females, age 19–53 years) participated in the experiment after giving written informed consent. The experimental setup was approved by the local ethics committee.

#### *Apparatus*

During the experiment, the observers stood behind a horizontal bar and grabbed a gamepad that was attached to the bar. We controlled stimulus generation and data acquisition using MATLAB with the Psychtoolbox extension (Brainard, 1997; Pelli, 1997). Visual stimuli were presented through a stereoscopic head mounted display (Kaiser SR80) with a field of view of 63◦ (horizontal) × 53◦ (vertical), a resolution of 1280 × 1024 pixels for each eye, with 100% overlap, and a 60 Hz refresh rate. We fixed the inter-pupil distance for the stereo projection at 6 cm for all observers. The observers' head movements (i.e., translation and rotation) were monitored by four high-speed motion capture cameras (Vicon® MX 13) with a 120 Hz sampling rate; they were used for online stereo projection and offline head movement analysis. The stereo presentation setup allowed the observers to feel immersed in the virtual environment.

#### *Stimuli*

The visual stimulus consisted of 50 cone-shaped 3-dimensional (3-D) objects (**Figure 1**). The cones were of 7 cm radius and 30 cm height and moved inside an imaginary cube (200 × 200 × 200 cm) located at the observer's eye height. The mean viewing distance, from the observer to the center of the imaginary cube, was 120 cm (the cone distances ranged from 20 to 220 cm), 160 cm (the cone distances ranged from 60 to 260 cm), or 200 cm (the cone distances ranged from 100 to 300 cm). The cones moved at 75 cm/s in a direction randomly determined for each cone; each cone's direction changed every 333 ms. When the center of the cone's mass (i.e., three quarters of the middle line down from the vertex) reached a cube wall, it was reflected from the wall. The cones had a direction (i.e., based on the orientation of their tips, **Figure 1B**). In the ME condition, the cones were pointing toward the observer's chest. In the TAR condition, the cones were pointing toward an invisible target placed 340 cm away from the observer. In the RND condition, the cones were pointing in pseudo-random directions. The cone directions in the RND condition were determined based on an algorithm similar to that used by Gao et al. (2010). The tip of a cone directed off a virtual line from the center of the cone to the center of the imaginary cube by a specific degree ranging from −90◦ to 90◦. The deviation amount was fixed for each cone and was randomly determined. This made the motion profile of each cone as similar as possible for the different cone direction conditions.

### *Procedure*

A button press started the trial. After viewing a blank screen for 0.5 s, the observer viewed the moving cones for 5 s. After the visual stimuli disappeared, a probe circle appeared at a random distance (110–210 cm away) from the observer. The observer indicated the center of the imaginary cube by moving the probe along an invisible line, which was extended horizontally through the middle of the imaginary cube, and pressing a button (**Figure 1A**).

We used a 3 × 3 within-subjects design. The factors were viewing distance (3 levels: 120, 160, and 200 cm), and cone direction (3 levels: ME, TAR, and RND). Each condition was repeated six times resulting in 54 trials, which were presented in a random order. Before the experiment, the observers were allowed to practice as long as they wanted.

#### **RESULTS**

After removing values that deviated greater than 3 standard deviations from the overall mean computed for all observations (i.e., the outlier observations), the data were submitted to a mixed model analysis with the within-subjects factors of viewing distance and cone direction. We also reported partial eta squared (η2 *p*) values derived from the data aggregated for each observer and for each of the conditions.

#### *Distance estimations*

**Figure 2A** shows the distance estimation results. As expected, the estimated distances differed depending on the viewing distance [*F*(2, 708) = 40.0, *p* < 0.001, η2 *p* = 0.67]. Thus, the observers could distinguish between the different viewing distances. Note the slopes were shallower than the veridical estimation 1 . That is, the observers underestimated the distance at 200 cm [*F*(1, 13) = 4.99, *p* = 0.044, η2 *p* = 0.28], and overestimated the distance at 120 cm [*F*(1, 13) = 5.95, *p* = 0.030, η2 *p* = 0.31]. No deviation from the actual distance was found in the 160 cm condition (*F* < 1).

The cone directions did not significantly bias the distance estimations [*F*(2, 708) = 0.61, *p* = 0.544, η2 *p* = 0.07]. However, we found a significant interaction between viewing distance and cone direction [*F*(4, 708) = 3.38, *p* = 0.009, η2 *p* = 0.26]. At the

1Distance perception in virtual environments is known to be distorted relative to real world distance perception (Loomis and Knapp, 2003; Thompson et al., 2004). Therefore, we were not surprised to observe effects in this direction. However, this was beyond the focus of the present study and we will not speculate further about the potential reasons for these effects.

**FIGURE 1 | (A)** A schematic illustration of the experiment. The participants viewed virtual cones moving inside an imaginary cube for 5 s, after which they indicated the center of the imaginary cube. **(B)** Example snapshots of a

visual image of the ME (all cones are facing the observer), TAR (all cones are facing an invisible target located behind the cones), and RND (the cone orientations are random) conditions.

Positive values indicate accelerations toward the cones. The error bars indicate the standard error of the mean.

160 cm viewing distance, the estimated distance was significantly shorter in the ME condition compared to the TAR condition [*F*(1, 151) = 4.37, *p* = 0.038, η2 *p* = 0.28] and the RND condition [*F*(1, 149) = 6.72, *p* = 0.010, η2 *p* = 0.23]. On the other hand, at 120 cm, the estimated distances in the RND condition were significantly shorter than in the TAR condition [*F*(1, 150) = 6, *p* = 0.016, η2 *p* = 0.63] and tended to be shorter than in the ME condition [*F*(1, 149) = 3.81, *p* = 0.053, η2 *p* = 0.22]2 . At the viewing distance of 200 cm, we did not observe an effect on cone direction (*F* < 1).

#### *Head movements*

We examined head movements along the depth axis. **Figure 2B** shows the observers' head accelerations in each of the conditions, averaged over 5 s. The head acceleration differed significantly between the cone direction conditions [*F*(2, 700.2) = 3.78, *p* = 0.023, η2 *p* = 0.28], irrespective of viewing distance (i.e., no interaction between viewing distance and cone direction, [*F*(4, 700.4) = 1.14, *p* = 0.336, η2 *p* = 0.10]. In the ME condition, the observers accelerated their heads more strongly away from the cones than in the TAR condition [*F*(1, 462.4) = 6.43, *p* = 0.012, η2 *p* = 0.41], or in the RND condition [*F*(1, 463.2) = 4.19, *p* = 0.041, η2 *p* = 0.33]. For the velocity of the head movements, the effect of viewing distance, cone direction, and the interaction were not statistically significant (*F*s < 1.32, *ps* > 0.26).

#### **DISCUSSION**

The results of Experiment 1 suggested that the cone direction modulated the distance estimations; this modulation effect depended on the viewing distance. The cones facing toward the observers were perceived as closer when they appeared in the viewing distance of 160 cm. Furthermore, the observers moved away from the cones more strongly when the cones faced them, which implies avoidance behavior. A post-experiment questionnaire also suggested that the observers experienced the cones facing them as more negative (less friendly or more threatening) than those facing the other directions. Thus, the modulation of the distance estimations might be related to the observers' negative impressions of the cones. In Experiment 2, therefore,

2It is unclear why the cones of random directions were perceived as closer at the short viewing distance. At the short distance, the cones of random directions might have appeared as more crowded and less organized. Consequently, they might have "overwhelmed" the observers to a greater extent than the

cones of the more ordered conditions, and were thus perceived as closer. Because our primary interest was the effect of the cones facing toward the observers, we did not provide an in-depth discussion of the comparisons between the RND vs. the ME and the TAR conditions.

we directly tested whether cone direction affected the subjective impression of the cones.

#### **EXPERIMENT 2**

#### **MATERIALS AND METHODS**

Nine paid volunteers (2 females, age 19–24 years) participated after giving a written informed consent. The material and methods were identical to those of Experiment 1 except for the following. The observers sat on a chair and wore a different head mount display (Sony HMZ-T2). Their head movement was not monitored. After the 5-s stimulus presentation, the observers rated the "friendliness" of the cones on a 7-point scale with the poles labeled as "hostile" and "friendly" by mouse clicking.

#### **RESULTS**

**Figure 3** shows the results of Experiment 2. The cone direction affected the friendliness ratings of the cones [*F*(2, 469) = 88.0, *p* = 0.001, η2 *p* = 0.62]. The cones were rated as less friendly (or more hostile) in the ME condition than in the TAR condition [*F*(1, 310) = 49.7, *p* < 0.001, η2 *p* = 0.49], which were in turn rated as less friendly than in the RND condition [*F*(1, 310) = 45.2, *p* < 0.001, η2 *p* = 0.58]. In addition, viewing distance significantly modulated the friendliness ratings [*F*(2, 496) = 4.49, *p* = 0.012, η2 *p* = 0.28], which increased linearly with the viewing distance [*F*(1, 472) = 9.02, *p* = 0.003, η2 *p* = 0.31]. The interaction between viewing distance and cone direction was not statistically significant (*F* < 1).

#### **DISCUSSION**

The cones were rated as friendlier when they were facing the target rather than the observer, and when they were further away. The effect of distance estimations depended on viewing distance. In contrast, the effect of cone direction on the friendliness ratings did not depend on viewing distance. Although the decreased perceived friendliness of the cones that faced the observer is one factor that affected the distance estimations, other factors affected the pattern of distance estimates.

#### **EXPERIMENT 3**

First, we tested whether the observed effects were specific to a virtual reality setup using a head mounted display which allowed head movements. To do so, we used a projection screen with shutter glasses to emulate 3-D vision with the head fixed. Second, we wanted to clearly identify the distance at which the effect was observed. Therefore, we concentrated on the distance difference between the ME and TAR conditions and examined the effect of cone direction at seven different viewing distances. Last, we wanted to determine the within-participant relationship between the distance estimates and the friendliness ratings.

#### **MATERIALS AND METHODS**

Nineteen paid volunteers (12 females, age 19–27 years) participated after giving a written informed consent. The visual stimuli were presented on a large screen by a 3D stereo projector (Sight 3D, Solidray Co. Ltd.) and stereo shutter glasses (3D Vision, NVIDIA). The refresh rate of the projection was 120 Hz (i.e., 60 Hz for each eye). The screen was 133.5 cm (height) × 178 cm

(width). The height of the center of the screen above the ground was 144 cm.  The distance from the screen to the observer's eye position was 213.5 cm. The visual stimuli were identical to those used in Experiment 1 except for the following. Since the visual angle (field of view) was smaller than that in Experiment 1, the size of the imaginary cube was 100 × 100 × 100 cm and the number of cones was 25. In the ME and TAR conditions, we used 7 different distances from 100 to 220 cm at 20 cm intervals. We omitted the RND condition. The observers first engaged in the distance estimation procedure as in Experiment 1. Next, they rated the cones' friendliness as in Experiment 2. For the distance estimations, each stimulus was repeated six times. Hence, there were 84 trials. For the subjective ratings, each stimulus was presented once.

## **RESULTS**

#### *Distance estimations*

The results are shown in **Figure 4A**. We found statistically significant effects for cone direction [*F*(1, 1532) = 16.2, *p* < 0.001, η2 *p* = 0.33], and for viewing distance [*F*(6, 1532) = 2.7, *p* < 0.001, η2 *p* = 0.83]. There was a significant interaction effect found between cone direction and viewing distance [*F*(6, 1532) = 2.41, *p* = 0.025, η2 *p* = 0.15]. The distance estimations were significantly closer in the ME condition compared to the TAR condition only at the 200 cm and 220 cm viewing distances (*Fs* > 15.0, *ps* < 0.001). No differences were found at the other viewing distances (*Fs* < 1.95, *ps* > 0.165). Notably, the distance estimations were more veridical in Experiment 3 than in Experiment 1. We found no significant differences between the presented distances and the estimated distances at any of the viewing distances (*Fs* < 1.79, *ps* > 0.198).

#### *Friendliness ratings*

**Figure 4B** shows the average score of the friendliness ratings. The results were generally consistent with those of Experiment 2. The

cones in the ME condition were rated as less friendly than the cones in the TAR condition [*F*(1, 234) = 84.9, *p* < 0.001, η2 *p* = 0.51]. The effect of distance was also significant [*F*(1, 234) = 4.78, *p* < 0.001, η2 *p* = 0.24]. The friendliness ratings almost monotonically increased with the viewing distance. The viewing distance by cone direction interaction was not statistically significant (*F* < 1). Furthermore, the overall within-participant correlation between the distance estimations and the friendliness ratings was statistically significant (*r* = 0.13, *p* = 0.036). The positive correlation observed supports the relation between these two measures.

#### **DISCUSSION**

The results of Experiments 1 and 2 were at least partially replicated in Experiment 3, which used a different virtual reality presentation method. Consistent with Experiment 2, the cones facing the observer were rated as less friendly, irrespective of the viewing distance. Furthermore, the cone direction modulated the distance estimates; similar to the results of Experiment 1, this modulation depended on the viewing distance. We compared the results of Experiments 1 and 3. In both experiments, the cones facing toward the observers were perceived as closer. This effect depended on the viewing distances, and only the effective viewing distance was different between Experiments 1 and 3. This point is further addressed in the General Discussion section.

#### **GENERAL DISCUSSION**

The present study examined whether factors other than physical distance—the orientation of simple geometric objects influenced distance perception in a virtual environment. In Experiment 1, the observers estimated the virtual cones facing them as closer than the cones facing other directions, when the cones were presented at a certain distance (i.e., 60–260 cm away). Furthermore, the cone direction affected the observers' head movements (Experiment 1) and the subjective impression of the friendliness of the cones (Experiment 2). When the tips of the cones faced the observers, the observers moved away from the cones and rated the cones as less friendly (more hostile). These effects were observed irrespective of the viewing distance. Experiment 3 replicated the distance estimation and friendliness rating results, although the effective viewing distance was further away (greater than 150–270 cm).

The effect on distance perception could not be a direct effect of geometric factors. As a cone is a 3-D object, the position of the cone is somewhat ambiguous when referred to by a point-shaped probe. For example, if the tips of a cone served as a representative point, the cones facing toward the observers would be estimated as closer than the cones facing the opposite direction, when the center of the cones was located at the same position, as was the case in the present experiment. If these geometric factors played a role in the modulation of distance perception, then cone direction would have influenced distance perception irrespective of viewing distance. We found, however, that the modulation of distance perception due to the cone direction depended on the viewing distance, which is not consistent with an account based on a direct effect of geometric factors. Rather, the geometric factor—whether cones faced toward the observers or not—would affect the distance perception through mediating psychological factors, such as experienced unfriendliness or perception of a threat.

In Experiments 1 and 3, the observers perceived the cones facing toward them as closer, when the cones were presented at certain viewing distances. The effective viewing distances were, however, not the same; they were from 60 to 250 cm and 150 to 270 cm in Experiments 1 and 3, respectively. The visual stimuli differences—the size of the imaginary cube and the number of cones—might have caused the difference in the effective viewing distances. However, at the moment, we speculate that differences in the devices used for the 3-D stereo presentation were responsible for the dependency on the different viewing distance. Distance in virtual environments is not necessarily veridical, but sometimes distorted compared with real spaces (Loomis and Knapp, 2003; Thompson et al., 2004). The amount of distortion depends on the setup used. The lower slope of the estimated distance against the presented distance in Experiment 1 (**Figure 2A**) suggests that the presented distances might be mapped onto a smaller subjective range. This was less of a factor in Experiment 3, in which the presented and estimated distances matched more closely (**Figure 4A**). Consequently, the subjective ranges within which cone orientation influenced distance perception might have been even more similar than suggested by the presented distances.

Several psychological factors are known to influence distance perception. Many studies have examined such influences in real world situations with meaningful stimuli (Proffitt et al., 2003; Witt et al., 2004; Balcetis and Dunning, 2010; Alter and Balcetis, 2011; Cole et al., 2012; Xiao and Van Bavel, 2012). In contrast, the aim of the present study was to examine distance perception in a virtual environment with simple visual stimuli. The virtual cones could not physically hurt the observers (and the observers knew this); nevertheless, the observers perceived the virtual cones facing toward them as closer when they were presented at a specific viewing distance. Moreover, distance perception modulation was accompanied by observers' avoidance behavior and negative subjective impression of the cones (i.e., they were rated as less friendly or more hostile). Thus, distance perception modulation was observed even when the observers were aware that the reward or punishment was virtual.

The cones facing the observers at a specific viewing distance were perceived as closer. Perhaps the modulation of distance perception was mediated by the perception of an emotional threat and/or social discomfort. One possibility is related to the fact that pointy objects tend to evoke aversion (Morse and Cohen, 1983; Shabani and Fisher, 2006); the aversion evoked might have been stronger when the cone tips faced the observers. This fits with the avoidance behavior indicated by the head tracking data as well as the less friendly ratings. The cones might also trigger social processing related to the regulation of interpersonal distance. The observers' backwards movements when faced by the cone tips could be also considered as the signature of implicit avoidance behavior. This is consistent with the finding that observers in a virtual environment keep the larger distance with a virtual avatar facing toward them (Bailenson et al., 2003). Previous studies suggested that socially or emotionally negative targets in the real world were felt or perceived as closer (Cole et al., 2012; Xiao and Van Bavel, 2012). Another possibility to explain the effect of the cones' direction on the distance estimations is that the cones facing toward the observers might be perceived as potentially approaching them. Many studies suggested that approaching objects lead to specific (negative in most cases) perceptual and social states (Mühlberger et al., 2008; Tajadura-Jiménez et al., 2010).

Although the cones facing toward the observers were rated as less friendly regardless of the viewing distance, they were perceived as being closer at specific viewing distances. Therefore, even if perceived friendliness was related to the modulation of distance estimation, it would not be a direct cause of the modulation. The distance perception modulation might be related to the violation of personal space (Liberman et al., 2007). Wilcox et al. (2006) showed that objects in a virtual environment were felt as intrusive, when the viewing distance was less than 100 cm. The modulation of distance perception by the cones' direction might take place only when they appear near the intrusiveness boundary (i.e., the personal space boundary). Objects much closer than the boundary would be perceived as violating personal space, irrespective of their perceived friendliness, while objects far away from the boundary would be perceived as not violating personal space. On the other hand, when the objects were close to the boundary, the perception of them as intrusive and violating personal space might depend on their friendliness. At this specific viewing

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distance, the cones facing toward the observers that resulted in the negative reactions (i.e., avoidance behavior and less friendly ratings) might be felt as intrusive and violating; if they were facing another direction, they might be perceived as non-intrusive. A recent study demonstrated that the representation of personal space is sensitive to social factors (Teneggi et al., 2013). According to this view, the intrusive cones would be perceived as closer since they violated the observers' personal space (Schnall, 2011). Although these accounts are speculative, they warrant further investigation by combining a virtual environment, personal space, and distance perception.

In sum, the present study showed that the orientation of simple geometric objects in a virtual environment could influence their perceived distance from observers, their perceived friendliness, and implicit avoidance behavior. Several issues concerning distance perception in virtual environments remain open. For example, a direct comparison of distance perception using the same stimuli in a real and a virtual environment would help us understand how the disconnection from the real world (real rewards and punishments) affect our distance perception. The results of the present study suggest that the perception of an object as closer and having a negative impression about that object co-occur. In contrast, in the real world, we form positive and negative impressions of objects that are perceived as closer. For instance, desired objects are perceived as closer (Balcetis and Dunning, 2010). How virtual rewards affect distance perception, warrants further investigation. Our study also implies that distance estimation may serve as an objective measure for the strength of psychological reactions in the social domain in virtual environments. There has been an increase in the combination of social communication with virtual environments. Examining distance perception in virtual environments with an emphasis on psychological and social aspects will lead to the development and application of user-friendly technologies.

#### **ACKNOWLEDGMENTS**

This research was supported by JSPS KAKENHI (23240034, 25700013, 12F02779, 09J06479), JST CREST, and the National Research Foundation of Korea's World Class University program (Grant R31-10008). We would like to thank Nadine Simon for help in data collection.

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**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.

*Received: 14 June 2013; accepted: 28 August 2013; published online: 18 September 2013.*

*Citation: Takahashi K, Meilinger T, Watanabe K and Bülthoff HH (2013) Psychological influences on distance estimation in a virtual reality environment. Front. Hum. Neurosci. 7:580. doi: 10.3389/fnhum.2013.00580*

*This article was submitted to the journal Frontiers in Human Neuroscience.*

*Copyright © 2013 Takahashi, Meilinger, Watanabe and Bülthoff. 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) or licensor 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 role of potential agents in making spatial perspective taking social

## *Amy M. Clements-Stephens 1,2,3, Katarina Vasiljevic 3, Alexandra J. Murray3 and Amy L. Shelton1,2,3\**

*1 School of Education, Johns Hopkins University, Baltimore, MD, USA*

*2 Center for Talented Youth, Johns Hopkins University, Baltimore, MD, USA*

*3 Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA*

#### *Edited by:*

*Antonia Hamilton, University of Nottingham, UK*

#### *Reviewed by:*

*Leonhard Schilbach, University Hospital Cologne, Germany Dana Samson, Université Catholique de Louvain, Belgium*

#### *\*Correspondence:*

*Amy L. Shelton, School of Education, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA e-mail<EMAIL_ADDRESS>
A striking relationship between visual spatial perspective taking (VSPT) and social skills has been demonstrated for perspective-taking tasks in which the target of the imagined or inferred perspective is a potential agent, suggesting that the presence of a potential agent may create a social context for the seemingly spatial task of imagining a novel visual perspective. In a series of studies, we set out to investigate how and when a target might be viewed as sufficiently agent-like to incur a social influence on VSPT performance. By varying the perceptual and conceptual features that defined the targets as potential agents, we find that even something as simple as suggesting animacy for a simple wooden block may be sufficient. More critically, we found that experience with one potential agent influenced the performance with subsequent targets, either by inducing or eliminating the influence of social skills on VSPT performance. These carryover effects suggest that the relationship between social skills and VSPT performance is mediated by a complex relationship that includes the task, the target, and the context in which that target is perceived. These findings highlight potential problems that arise when identifying a task as belonging exclusively to a single cognitive domain and stress instead the highly interactive nature of cognitive domains and their susceptibility to cross-domain individual differences.

#### **Keywords: perspective taking, social skills, agency, individual differences, spatial cognition**

The ability to imagine the world from the point of view of another person comes in a variety of forms, from understanding another person's opinion on a discussion topic to literally imagining what the visual world would look like from their perspective. The latter, termed visual-spatial perspective taking (VSPT), has traditionally been considered a form of spatial problem solving. However, over the course of the last decade, there has been a growing body of research supporting a relationship between one's social abilities and the ease with which they are able to engage in this more visually driven form of perspective taking (Brunyé et al., 2012; Kessler and Wang, 2012; Shelton et al., 2012), highlighting the role of VSPT for everyday social interactions. Impairment on tasks that require adopting another's perspective—be it to judge if an object is visible from another viewpoint (Level 1 VSPT) or to represent what a spatial layout might look like from another viewpoint (Level 2 VSPT)—is a hallmark feature of Autism Spectrum Disorders (ASD; Baron-Cohen, 1992; Best et al., 2008). A vast majority of the research examining this relationship between social and VSPT abilities tends to come in two forms: either investigation of how/when VSPT abilities are impaired or preserved in individuals with ASD due to their known deficits in social skills (Hobson, 1984; David et al., 2006; Hamilton et al., 2009; Gould et al., 2011; Zwickel et al., 2011; Schilbach et al., 2012) or investigations of the natural variability that is observed in more typically-developing populations (Brunyé et al., 2012; Shelton et al., 2012).

One approach to understanding how social abilities might influence VSPT is through the investigation of the role that agents play in cognitive tasks. A wide range of literature on embodied cognition has investigated the conditions and tasks that appear to be sensitive to the presence of a human agent (Eppel et al., 1983; Schober, 1998; Ruby and Decety, 2001; Ames et al., 2008; David et al., 2008; Tversky and Hard, 2009; Kessler and Rutherford, 2010; Kessler and Thomson, 2010; Schilbach et al., 2012). For example, Schober (1998) has demonstrated that people will make an effort to adopt a listener's perspective when describing a spatial display, whereas they use their own perspective or neutral statements such as cardinal directions when asked to simply describe the display (no human listener). Similarly, Tversky and Hard (2009) asked individuals to describe spatial events depicted in scenes with or without the presence of another person in the scene. They found that the scene descriptions differed such that the participants spontaneously adopted the perspective of a person in a scene, even when such perspective taking was not relevant to the task. Moreover, they had no direct contact with the agent, suggesting that it was the mere presence and not any interactive requirement that motivated spontaneous perspective taking. Additionally, Schilbach et al. (2012) showed a sensitivity toward face-like stimuli that had a modulatory effect on performance when completing a gaze-mediated stimulus-response compatibility paradigm. When the social context of the stimuli was manipulated (face, face-like, or object stimulus), there was a reduction in the observed congruency effects for faces as compared to objects, suggesting that there was an effect of social context on action control. Based on these results, it is clear that human participants are sensitive to the presence of other human agents in ways that affect performance.

An alternative line of work has explored how agency might be attributed to objects (Zwickel, 2009; Zwickel et al., 2011; Zwickel and Müller, 2013). In a series of studies, Zwickel and colleagues set out to better understand VSPT when non-human entities were used as the target of perspective taking, both in typically-developing individuals (Zwickel, 2009; Zwickel and Müller, 2013) and those with ASD (Zwickel et al., 2011). This was first accomplished by examining whether individuals would adopt the perspective of geometrical shapes if the movement of the shapes appeared intentional. Intentionality was manipulated by using movements that implied interactions between the shapes. For example, when two triangles were moving about each other, they might evoke descriptions that reflect theory of mind (ToM) such as, "The small triangle surprised the large triangle." Zwickel (2009) presented individuals with either the systematic ToM movement or random movement and found that individuals spontaneously adopted the perspective of the probed triangle when the movement implied agency but not when the movement was random. Follow-up work on individuals with ASD showed that although they were able to understand that the triangles were interacting in one case (ToM condition) and not in the other (random condition), the additional attribution of agency did not occur as evidenced by less appropriate descriptions of the animations (Zwickel et al., 2011). Therefore, it was concluded that in the case of individuals with ASD, although the perceptual cues (type of movement) were sufficient to invoke intentionality, they did not imbue the triangles with agency. These studies highlight one possible feature, intentional movement, which may be necessary for non-human targets to be perceived as potential agents. However, it is unknown what the potential boundary conditions are associated with perceived agency and the minimal requirements needed for stimuli to evoke VSPT when the stimuli are static.

In addition to understanding how agency attribution impacts VSPT, an additional line of research has been focused more on investigating the direct relationship between social abilities and VSPT. In particular, Brunyé et al. (2012) assessed whether gender and sub-clinical autistic traits were not only predictive of VSPT, but could differentiate between the levels of VSPT. The VSPT tasks used in this study required participants to either determine whether a light was visible from the perspective of an avatar (Level 1) or whether the light was to the left/right of the avatar (Level 2) and participants completed the autism quotient (AQ; Baron-Cohen et al., 2001). The overall score on the AQ was used with higher scores being indicative of greater autistic-like traits. Results from this study found slowed reaction times for the Level 2 VSPT task in males and females with relatively high AQ scores, suggesting that individuals with more autistic-like traits had greater difficulty taking the perspective of the avatar. This relationship was not seen for the Level 1 VSPT task. Taken together, these findings suggest that even in sub-clinical healthy populations, having more autistic-like traits influences one's ability to engage in perspective taking when the judgment to be made goes beyond asking whether something might be visible in the alternative perspective and requires a more complex set of judgments to be made about the spatial properties of the visual scene from an alternative perspective.

In a similar manner, Shelton et al. (2012) focused more specifically on social skills by using a combined score derived from the AQ social and communication subscales. As such, a lower score on this combined AQ score would be associated with individuals who have strong social skills whereas a higher score would be more associated with individuals who are less socially savvy 1 . In this experiment, participants were seated in front of a display of three buildings with seven different colored potential targets of perspective taking oriented around the display at 45◦ intervals. Participants were presented with an image and were asked to identify which viewpoint was being displayed, whether it be their own or one of the potential targets. Agency was manipulated by having each participant complete three different conditions: artist figures, triangles, and cameras. It was hypothesized that artist figures would be more human-like than either the triangles or cameras, with triangles as clear inanimate objects and cameras as potential intermediaries of perspective (people look through them). A striking relationship was found. Participants with lower AQ combo scores (more social) were more accurate at taking the perspective of the artist figures (*r* = −0.584) than those with higher AQ combo scores (less social), whereas no such relationship was found for either the triangles (*r* = −0.084) or the cameras (*r* = −0.053) conditions. It should be acknowledged that all of the conditions used objects, but the relative amount of potential agency conveyed varied across the different conditions. As such, these findings point to another potential requirement for perceived agency, especially with respect to static images; that is, it may be necessary for the potential "agents" to possess some human-like qualities.

Not only do these studies provide indications as to what it means for an object to be perceived as a potential agent, they also introduce a framework for distinguishing when VSPT includes a social component or not. That is, VSPT may be primarily spatial and remain so when targets do not evoke the suggestion of social engagement, but VSPT may become more dependent on interactions with social skills when targets are more agent-like, allowing one's social skills to influence behavior for better or for worse. This offers a method for assessing what kinds of targets might make VSPT more or less social. In particular, we can use the correlation between VSPT performance and social skills as a measure of when VSPT is or is not incurring social skill influence. If a target is motivating the task to be a "socially relevant" form of VSPT, we expect a relationship between measures of social skill and VSPT performance. However, if a target is not incurring the agency necessary to motivate social relevance, we expect to

1One important note on social skills in this context is that the relevant dimension is likely to be one's understanding and appreciation of social attributes and situations rather than social-seeking behavior or extroversion. Throughout, we use this broader definition, suggesting a form of social intelligence or savvy rather than more strictly whether someone engages in more or less social activity .

see a "non-social" form of VSPT such that social skills are not correlated with VSPT performance. Critically, we do not predict opposite relationships for socially relevant and non-social VSPT, but rather suggest that the task can either be sensitive to social influence or not (see **Figure 1**).

Using this approach to assess social influence, we can begin to ask deeper questions about what targets, target features, and conditions change the way an individual approaches the VSPT task. First, we can test how changing basic features might influence the degree to which a target seems to acquire agency that brings social skills to bear. In the previous study (Shelton et al., 2012), we used brute force differences (human form vs. inanimate objects), but more subtle information can also be manipulated. For example, we can manipulate the presence or absence of very basic facial features. Second, we can ask whether and how experience with one type of target might modulate the perceived agency of another target, which we refer to as experiential context. In the previous study (Shelton et al., 2012), there was no effect of order, suggesting that having seen the artist figures first did not make the triangles more or less sensitive to the influence of social skills. Moreover, seeing the triangles followed by artist figures did not make the artist figures more or less sensitive. However, as noted above, these were already different classes of objects. Here we consider what happens to perceived agency when targets share certain features but not others.

To address these issues, we ran a series of experiments that compare the original targets from the previous study, plain triangles and artist figures, to other variations that might convey more or less agency as evidenced by an influence of social skills on VSPT performance. First, we set out to establish whether adding human-like features to an object would increase the sensitivity to social skill influence. In Experiment 1, we compared plain triangles to triangles with eyes affixed to them, making them appear more human-like (or at least Muppet-like) via visual features. In Experiment 2, we compared the artist figures

**FIGURE 1 | Potential framework depicting the relationship between social skills and VSPT performance for proposed socially-relevant and non-social VSPT.** The distinction between these two types of tasks is captured by the degree to which VSPT is incurring a social skill influence indexed by the magnitude of the correlation.

condition from our previous study, which showed the relationship between social skills and VSPT, to agents with even more human-like qualities, fashion dolls. In both Experiments 1 and 2, we contrasted conditions that vary on known visual features and counterbalanced order to allow us to explore any modulation of the social skill relationships due to experiential context. Lastly, we wanted to ask whether we could increase sensitivity to social skill influence by conceptually manipulating the meaning of a target of perspective taking. In Experiment 3, we return to the plain triangles, but now refer to them as "Aliens" in an effort to convey that these could be creatures with agent-like qualities. This manipulation allowed us to ask whether a conceptual cue to agency can be robust enough to bring about the influence of social skills on VSPT performance. Overall, results from these studies reveal the complexity of the relationship between social skills and VSPT, highlighting the susceptibility of individual differences to contextual and cross-domain influences.

## **GENERAL MATERIALS AND METHODS**

All three of the correlational experiments used the same basic paradigm, varying only the target of the VSPT task.

#### **PARTICIPANTS**

All participants were Johns Hopkins University undergraduate students between the ages of 18–22 who participated in return for extra credit in psychology courses. All procedures were approved and conducted in accordance with the Johns Hopkins Homewood Institutional Review Board. For all studies, inclusion in the study was based on the 0◦ orientation trials (described in more detail in the subsequent section). Because this type of VSPT task is difficult and a wide range of scores is typically observed, we did not want to exclude individuals merely because they fell along the lower end of the distribution. Therefore, we reasoned that if participants could correctly identify their own view, then we could assume that they understood and were engaged in the task. As such, we excluded individuals who made more than one error on these trials. Across all of the experiments, this criterion seemed to successfully separate those who were on task from those who were not. Moreover, for each experiment, an effort was made to obtain approximately equal numbers of males and females. The analyses for each experiment included examining potential differences in performance between the genders. Consistent with previous findings obtained by Shelton et al. (2012), the differences between males and females on all measures and correlations were negligible and will not be discussed further.

#### **MATERIALS, DESIGN, AND PROCEDURES**

For each experiment, participants completed a set of measures that included the three buildings task, paper-and-pencil spatial skill tests, and a self-report questionnaire (the AQ described below) in a pseudorandom order. The spatial skill tests administered are part of a standard battery of measures typically included across all experiments in the lab; they were not pertinent to the hypothesis-driven questions being addressed and had little or no relationship to the outcomes presented below.

#### *Three buildings (3Bldgs) task*

Participants completed the 3Bldgs task, which is an adaptation of Piaget's three mountains perspective-taking test (Piaget and Inhelder, 1967). For this task, participants viewed two different displays. Each display consisted of three unique buildings (6 different buildings total) with each building constructed out of LEGO® building blocks (Lego Group, Billund, Denmark) and placed on 24 diameter plastic disks that were covered in faux grass mats. Each display disk was centered on a 36 diameter wood table and photographed from 8 different orientations separated by 45◦ increments. Around the building display were seven uniquely colored targets for perspective taking (red, blue, white, black, purple, yellow, and orange). Targets were placed at 45◦ intervals and corresponded to headings of 45◦, 90◦, 135◦, 180◦, 225◦, 270◦, and 315◦ with respect to the participants' designated view of 0◦. The targets were manipulated across the set of experiments to assess the potential impact on the perceived agency (see **Figure 2**) and are described in greater detail with the corresponding experimental manipulation.

Participants were seated in front of the physical display and viewed images on a laptop computer. Each presented image corresponded to the would-be visual perspective of one of the targets or to the participant's own perspective (0◦). Participants were asked to identify the perspective of the image. For each image, irrespective of the task version, the participant was asked, "Which <TARGET> is at this view?2 " Participants indicated their response by pressing a key corresponding to the color of the target or the spacebar to indicate that it was his/her own view. Each task version consisted of 40 self-paced trials (5 trials at each

**(Experiments 1 and 3), upper right (Experiment 1), lower left and right (Experiment 2).**

orientation) with a 5-s response deadline. Response latency and accuracy were measured.

The 0◦ orientation (where the participant was seated) was selected randomly for each participant from one of 4 possible orientations. For each display, the four candidate orientations were selected by randomly choosing one orientation and using the 3 additional orientations that were opposite and orthogonal to that initial orientation. For a given start orientation, targets were placed at the remaining seven orientations. When appropriate, display-condition assignment and order of conditions were counterbalanced, and the order of the target colors around the display was selected randomly for each participant and kept constant for both conditions (when applicable).

### *Autism quotient (AQ; Baron-Cohen et al., 2001)*

The AQ is a self-report questionnaire designed to assess the degree to which individuals vary on five traits typically associated with ASD—social skills, perseveration, attention to detail, communication, and imagination—with higher scores (overall and each subscale separately) reflecting stronger ASD-like traits. For the set of experiments presented here, the critical scales of interest are the social and communication impairment scales, which are designed to capture behaviors on a continuum from socially appropriate to socially inappropriate behaviors. Due to the strong correlation observed in Shelton et al. (2012) between the social and communication impairment subscales, we used the same combined social/communication score as the previous study. For clarity, we term this the social ineptitude score, reflecting the fact that higher scores mean less social. This social ineptitude score is used in all analyses for each experiment.

### **EXPERIMENT 1: TRIANGLES WITH AND WITHOUT EYES**

In this experiment, we set out to assess whether objects could be made sensitive to the influence of social skills by adding features suggestive of agency. Specifically, participants were asked to complete two conditions in which they either took the perspective of a triangle (plain triangles condition) or took the perspective of a triangle that had eyeballs affixed to the top of it (triangles-with-eyes condition). First, we expected no relationship between social skills and performance with plain triangles, replicating our previous work. For the triangles-with-eyes condition, we used the magnitude of the correlation between social skills and performance as an index to determine whether eyeballs were sufficient for inducing potential agency in an object. If any sign of agency "socializes" the task, then we might expect a correlation comparable to that observed for the artist figures in Shelton et al. (2012). However, we may also see a gradation of social skill influence dependent upon the degree of potential agency induced, in which case the triangles-with-eyes would show a weaker correlation than other more agent-like targets. Such a result would necessitate additional comparisons. Finally, we might see that static triangles are objects regardless of whether they have eyes or not, with no correlation observed in either condition.

In addition to the basic comparison of triangles with and without eyes, we also entertained the possibility that the order of the conditions could affect observed correlations. Given that these two conditions use the same basic object, they may provide a

2This question was intentionally vague to limit potential bias in the language that might influence how the participant should interpret the task and the target. Using language such as "Who sees this... ?" might affect interpretation of agency (i.e., "who" denotes a being; "seeing" is a property of an agent). We also acknowledge that this wording does not explicitly tell the participant to mentally visualize the space. As such, it is possible that some participants engaged more or less visual imagery as opposed to other forms of spatial reasoning. However, we have no reason to suspect that this same variability in strategy does not hold for all VSPT tasks.

more direct contrast of their potential agency than the triangles, cameras, and artist figures used in our previous research study (Shelton et al., 2012). As such, we considered whether seeing the plain triangles first might imbue the subsequent triangles with eyes with more agency than they might convey on their own (when experienced first). This might result in the correlation for triangles-with-eyes being weaker when performed first than when performed after plain triangles. Plain triangles provide an even more interesting case in that they are expected to show no correlation, especially if experienced first. However, it is possible that seeing triangles-with-eyes as potential agents could carryover to subsequent performance with plain triangles, making them more sensitive to the social skill influence.

#### **MATERIALS AND METHODS**

#### *Participants*

For this experiment, 78 naïve participants were enrolled. Six participants (2 males) failed to meet criterion, leaving 72 participants (34 males) included in all subsequent analyses.

#### *Materials, design, and procedures*

Participants completed two versions of the 3Bldgs task using plain triangles and triangles with eyes as targets. Using a set of 14 identical wooden triangular blocks, we created two sets of seven different colored triangles (see above) placed on plain wood pedestals (13 total height). One set served as the plain triangles condition. For the second set, 1 round wooden eyeballs painted white with black circles were affixed to the top of each triangle to create the triangles-with-eyes condition (see **Figure 2**). For each image, irrespective of the task version (plain triangles/triangleswith-eyes), the participant was asked, "Which Triangle is at this view?" Each participant completed both versions of the task using two different displays. Display-condition assignment and order of conditions were counterbalanced. After applying the exclusion criterion, we had approximately equal numbers in each order (plain triangles first *n* = 34). The order of the target colors around the display was selected randomly for each participant and kept constant for both conditions.

#### **RESULTS**

Mean response latency (overall and for correct trials only) and overall accuracy were calculated for both versions of the 3Bldgs task and were separately subjected to a mixed ANOVA with order as a between-subjects variable and target (plain triangles/triangles-with-eyes) as a within-subjects variable (**Figure 3**). For response latency, there were no significant effects or interactions (all *p*s > 0.11). For accuracy, we found that the group that performed the plain triangles first were significantly less accurate than the group that performed the triangleswith-eyes condition first, *F*(1, 70) = 5.75, *p* = 0.019, η2 *G* = 0.05. Although this effect was significant, it was a small effect, accounting for only about 5% of the measured variance. Moreover, we also observed that participants were significantly more accurate on the triangles-with-eyes condition than the plain triangles condition, *F*(1, 70) = 5.98, *p* = 0.017, η2 *G* = 0.02. Again, this was a small effect (2% of the measured variance). There was no significant order × target interaction, *F*(1, 70) = 1.97, *p* = 0.165.

Although these effects are fairly small, it suggests that it may be important to consider whether some targets' perspectives are more readily adopted overall, and, more critically, the role order may play when investigating the relationship between social skills and performance on our VSPT conditions.

In addition to assessing conditional differences, we also correlated the performance on the plain triangles and triangles-witheyes conditions. Accuracy was positively correlated, *r* = +0.44, *p* < 0.001. This relationship is consistent with our previous study (Shelton et al., 2012) and suggests that there is a common spatial component to the VSPT task, irrespective of target condition.

To answer the critical question of social skill influence on VSPT performance we explored the correlations between social skills and accuracy 3 on the VSPT task for the two target conditions overall and then for each order separately. All correlations are significant at α = 0.05, corrected for the size of the relevant subset of correlations investigated unless otherwise specified. Consistent with Shelton et al. (2012), we observed a significant correlation between the social and communication impairment subscales from the AQ (*r* = 0.42); therefore, due to this observed relationship and to be consistent with previous literature we used a combined scored (social ineptitude score) in all analyses (see **Table 1** for separate correlations with subscales). Lower values on the social ineptitude score would be associated with better social skills, whereas higher values on the social ineptitude score would be associated with poorer social skills. Overall, we observed no correlation for the plain triangles condition, *r* = −0.18, *p* = 0.12 and a negative correlation for the triangles-with-eyes condition, *r* = −0.46, indicating that more social individuals had better performance than less social individuals for the triangles-witheyes condition. A *t*-test for non-independent *r*'s was conducted and revealed that these correlations were significantly different, *t*(69) = 2.45, *p* = 0.02, suggesting that adding eyes to the plain triangles allowed objects to become sensitive to social skill influences in VSPT.

An examination of the effect of order on these correlations paint a more complex picture, as can be observed in **Figure 4**, which shows the correlations for both conditions separately for each order. For the triangles-with-eyes condition, the correlation

3Consistent with previous data, response latency had no significant correlations (strongest was *r* = +0.1).

**Table 1 | Summary of correlations (and** *p***-values) between the relevant social skill scores and each condition, overall and by order of conditions where relevant.**

*All p-values presented are uncorrected for multiple comparisons; \*indicates the correlations that survive the correction for multiple comparisons within related subsets.*

was significant regardless of the order in which the conditions were completed, *r* = −0.46 and −0.45, supporting the claim that placing eyes on the simple triangles was sufficient to bring about the social skill influence. Performance on perspective taking with plain triangles had previously not shown a significant correlation with social skills (Shelton et al., 2012), and that was again the case when this condition was performed as the first condition, *r* = +0.13, *p* = 0.48. However, when the plain triangles followed the triangles-with-eyes, there was a significant negative correlation, *r* = −0.43, that was not significantly different from those observed for the triangles-with-eyes in either order, *p*s > 0.45. Additionally, this correlation was significantly different from the correlation when the plain triangles were viewed first as evidenced by a *z*-transform for independent correlations, *z* = −2.35, *p* = 0.009. As such, plain triangles incurred as much influence from social skills as triangles-with-eyes when participants had experienced the triangles-with-eyes first.

In cases where we observed a correlation with the social ineptitude score, we also compared their magnitude to the correlation observed for artist figures in the previous study (*r* = −0.58; Shelton et al., 2012) using a *z*-transform for independent correlations. None of the comparisons were significant, all *p*s > 0.16, suggesting that the triangles-with-eyes and the plain triangles (when presented after the triangles-with-eyes condition) were showing correlations in the same range as previously observed for artist figures.

#### **DISCUSSION**

The goal of Experiment 1 was to determine whether an object previously shown to be insensitive to social skill influence could be made sensitive by adding an agent-like feature. Adding eyes to triangles had two important impacts on performance. First, we did observe the significant correlation between performance on the triangles-with-eyes condition and social skills, suggesting that features such as eyes can create targets of perspective taking that are sensitive to the influence of social skills. In essence, it appears placing static features on an object may convey a sense of agency similar to what was observed for animating shapes (e.g., Zwickel, 2009). In addition, we observed that our plain triangles could also be imbued with some agent-like attributions by simply following the experience of the task with the triangleswith-eyes.

It is tempting to argue that the act of performing the task with an implied social context might keep participants in a state of "social-ness" rather than actually imparting the agency or sociality on the plain triangles. This seems unlikely given that we failed to find any order effects (or even trends that would suggest order effects) in the previous study (Shelton et al., 2012) and pilot work when the targets were different kinds of objects. Instead, it seems that the shared properties of the triangles with and without eyes may have allowed the agency (or sensitivity to social influence) induced by the eyes to carry over. In Experiment 2, we examine a variation on this carry over effect by contrasting two different representations of human form.

#### **EXPERIMENT 2: ARTIST FIGURES AND FASHION DOLLS**

Experiment 1 started with an object and examined whether we could induce sensitivity to social skill influence. In Experiment 2, we started with the artist figures that were first used to demonstrate the correlation between social skills and VSPT in this paradigm and compared them to a target with more humanlike features to assess whether the correlation might be sensitive to the degree or extent of implied agency. In addition, we again varied the order of the conditions to examine whether experience with the putatively stronger potential agent might strengthen or weaken the sensitivity of the putatively weaker potential agent.

#### **MATERIALS AND METHODS**

#### *Participants*

For this experiment, 82 naïve participants were enrolled. Ten participants (5 males) were excluded due to failure to reach criterion, leaving 72 participants (30 males) eligible for all subsequent analyses.

## *Materials, design, and procedures*

Participants completed two versions of the 3Bldgs task. In the artist figures condition, each target was a 13 tall wooden artist figure with its head painted one of seven unique colors. In the fashion dolls condition, we used a set of 7 distinct Barbie™ dolls (Mattel, Inc., El Segundo, CA), with each fashion doll wearing a colored dress corresponding to the colors used in the artist figures condition (see **Figure 2**). For each image, irrespective of the task version (artist figures/fashion dolls), the participant was asked, "Which Doll is at this view?" Each participant completed both versions of the task using two different displays. Display-condition assignment and order of conditions were counterbalanced. After applying the exclusion criterion, we had approximately equal numbers in each order (artist figures first *n* = 38). The order of the target colors around the display was selected randomly for each participant and kept constant for both conditions.

#### **RESULTS**

Mean response latency (overall and for correct trials only) and overall accuracy were calculated for both versions of the 3Bldgs task and were separately subjected to a mixed ANOVA with order as a between-subjects variable and target (artist figures/fashion dolls) as a within-subjects variable (see **Figure 5**). For both response latency and accuracy, there were no significant effects or interactions (all *p*s > 0.23 for response latency and all *p*s > 0.07 for accuracy). Again, we observed a significant positive correlation between accuracy with fashion dolls and accuracy with artist figures, *r* = +0.46, *p* < 0.001.

Given the observed correlation between the social and communication impairment subscales from the AQ (*r* = 0.69), all subsequent correlations were run between the social ineptitude score and the accuracy on the two agency conditions overall and then for each order separately (see **Table 1** for separate correlations with subscales). All correlations are significant at α = 0.05,

corrected for the size of the relevant subset of correlations investigated unless otherwise specified. Overall, we observed a negative correlation for the fashion dolls, *r* = −0.40, indicating better accuracy with better social skills. Surprisingly, no such correlation was observed for the artist figures, *r* = −0.08, *p* = 0.52. This is contrary to our previous studies where we have consistently observed this correlation (Shelton et al., 2012). A *t*-test for non-independent *r*'s confirmed that these two correlations were significantly different from each other, *t*(69) = 2.82, *p* = 0.006.

The unexpected result in the artist figures overall made the motivation for examining order effects even stronger. **Figure 6** shows the correlations broken down by order. For the fashion dolls, the correlation between social ineptitude score and performance was weaker when fashion dolls were presented first, *r* = −0.33, *p* = 0.04 uncorrected, but met the criterion for multiple comparisons when fashion dolls were presented second, *r* = −0.52. Although the correlation numerically increased when fashion dolls were presented second, the difference between the two correlations was not significant, *z* = 0.97, *p* = 0.17, suggesting that the correlation was similar irrespective of order. An examination of the artist figures condition revealed a more complicated picture. That is, when artist figures came first, performance showed a correlation with the social ineptitude score similar to what was observed previously (Shelton et al., 2012), *r* = −0.39, *p* = 0.02 uncorrected (comparison to *r* = −0.58, *z* = 1.33, *p* = 0.09), but when these same artist figures followed the experience with fashion dolls, the correlation with the social ineptitude score was weak and in the opposite direction, *r* = +0.14, *p* = 0.39. The correlations for the artist figures in the two different orders were significantly different, *z* = 2.26, *p* = 0.001, suggesting that the social skill sensitivity was modulated by the context in which the particular targets were experienced.

#### **DISCUSSION**

Experiment 2 provides a second example of how the degree to which a target of perspective taking appears to be socially relevant can be influenced by the experience of other targets. Artist figures, which were used to establish the initial correlation between social skills and VSPT in this paradigm, were essentially stripped of their sensitivity to social skill influence when they were experienced after performing the task with fashion dolls.

Although both Experiments 1 and 2 demonstrate how context can affect the sensitivity to social skill influences, the results may seem contradictory. In Experiment 1, having the putatively more agent-like target first increased the sensitivity for the subsequent less agent-like target, whereas Experiment 2 showed the opposite effect. However, the figures used in Experiment 2 were not the same object varying in a feature or two; they were two different representations of human form that varied on a variety of visual features (continuity of form, faces, hair, clothing, etc.). Although the artist figures can clearly convey agency in a way that allows a social skill influence, they are also affected by the context in which they are experienced.

The broader issue of context effects and target influences will be addressed in more detail in the General Discussion, but first we turn our attention to another form of context. All of our manipulations of potential agent-like features so far have been visual features. It is also possible to create conditions in which objects might be viewed as agents via conceptual context. Whether we can induce sensitivity to social skill influence using a conceptual context is the question for Experiment 3.

### **EXPERIMENT 3: TRIANGLE "ALIENS"**

One of the clear conclusions of Experiments 1 and 2 is that objects can be sensitive to social skill influences as a function of having features that suggest potential agency. Whether affixing eyes to simple shapes or using representations of the human form, these features appear to affect how individuals approach the perspective-taking task. We also observed a form of conceptual carryover from the triangles-with-eyes to the plain triangles. As a final test, we asked whether a purely conceptual manipulation could also make an object sensitive to social skill influence. Using the plain triangles again, we offered an alternative interpretation of the triangles as potential agents by calling them "aliens" during the perspective-taking trials. If triangles with eyeballs on top motivate the task to become more social in nature, then perhaps simply suggesting a type of being, be it alien or otherwise, might operate in a similar manner.

#### **MATERIALS AND METHODS**

#### *Participants*

For this experiment, 53 naïve participants were enrolled. Five participants (3 males) failed to meet criterion, leaving 48 participants (24 males) included in all analyses.

#### *Materials, design, and procedures*

Participants completed the 3Bldgs task using the same 7 triangular blocks on pedestals described in Experiment 1. For each image the participant was asked, "Which Alien is at this view?" Across participants, the display type was counterbalanced and the order of the target colors around the display was selected randomly for each participant.

#### **RESULTS AND DISCUSSION**

Mean response latency was 3018 and 3054 ms overall and for correct trials only, respectively, and overall accuracy was 72.9%. Again, we observed a significant correlation between the AQ social and communication impairment subscales, *r* = +0.46, so we again used the social ineptitude score (see **Table 1** for separate correlations with subscales). The critical correlation between the social ineptitude score and performance on the VSPT task with triangle aliens was significant, *r* = −0.36 (see **Figure 7**). Moreover, this correlation was not significantly different from the correlation obtained for the triangleswith-eyes condition either overall or separated by order in Experiment 1, *p*s > 0.65. These results suggest that even in the absence of a visual feature, an object can become sensitive to social skill influence on VSPT through conceptual suggestion.

## **GENERAL DISCUSSION**

One of the key motivations for this special issue on developing a framework for integrating the "social" and the "spatial" is the recent acknowledgment of a clear relationship between VSPT and aspects of ones savvy in social situations (Hamilton et al., 2009; Zwickel et al., 2011; Brunyé et al., 2012; Shelton et al., 2012). By definition, VSPT tasks involve the need to consider/imagine/reason about a target perspective that is different from one's own. As such, it is tempting to conclude that VSPT is both a spatial and social task. However, these tasks can vary dramatically with respect to who or what is the placeholder for the target perspective. Our previous work has shown that the relationship between VSPT performance and social skills depends on the nature of the target; targets that could be seen as potential agents were sensitive to social skill influence, whereas targets that did not have agent-like features were insensitive (Shelton et al., 2012). These and similar results (Zwickel, 2009; Zwickel et al., 2011; Schilbach et al., 2012; Zwickel and Müller, 2013) suggest that VSPT tasks *acquire* some social relevance when the target has potential agency. Using correlations between measures of social skills and performance on VSPT, the present study offers a more detailed account of what features and conditions can affect the degree to which any given target might convey agency and become sensitive to social skill influence.

One of the first implications of the present work is that simple physical features can induce an object to be sensitive to social skill influence. In the previous study, the physical form of a wooden artist figure appeared to motivate participants to engage the VSPT

**FIGURE 7 | VSPT performance as a function of social ineptitude score for the triangle aliens condition.**

task in a more social manner than either plain triangles or cameras (Shelton et al., 2012). Although triangles do not resemble human forms, in the present study, we were able to observe the same social skill influence on VSPT by simply adding eyeballs to the triangles. This small featural change seemed to push participants to engage the triangles as if they were potential agents, like the artist figures. Taken together, this body of work suggests that there are different visual features that can motivate one to perceive an object as a potential agent. The global shape of the artist figures likely conveyed the sense that this could be a person form, whereas the presence of eyes (which the artists figure did not actually have) likely conveyed a similar sense for triangles. These differences raise important questions about what other features or combinations might be more or less effective in engaging the social mechanisms that appear to be brought to bear, but they establish the very basic notion that minimal change can assert a strong influence.

In addition to the observation that physical features can induce agency, we also observed that the context defined by experiences surrounding the introduction of particular targets in perspective taking can also play a role in the perceived potential agency. First, we found that when a target closely resembles another object that has recently been attributed with agency, the similarity of object features may be sufficient to convey carryover agency. Performing VSPT with plain triangles as targets is generally insensitive to social skill influence when performed prior to other conditions or in the context of artist figures or cameras. That is, on their own, they are not potential agents. Despite their fundamental characterization as inanimate objects, these same plain triangles can be engaged as if they were potential agents when they immediately follow experience with identical triangles with eyes affixed to them. In other words, experiencing triangles-with-eyes as agents allowed plain triangles to be viewed as agents.

The artist figures provide a second case of experiential context. When performing the task with artist figures in the context of plain triangles or cameras, the artist figures represent the condition that shows the strongest numerical relationship between social skills and performance (Shelton et al., 2012). Similarly, when participants experienced the task with the artist figures first in Experiment 2, we saw a similar performance-social skill correlation to other "agent" conditions. However, when participants experienced the artist figures after exposure to the fashion dolls, this correlation was diminished completely for the artist figures condition, such that it had the same magnitude correlation as plain triangles alone. In this case, it was as if experiencing the fashion dolls as agents made the artist figures seem not only *less* agent-like but not at all agent-like, akin to a purely inanimate object.

As noted previously, the two types of triangles and two types of dolls represent opposing effects of experiential context (for a more in-depth discussion of experiential social context or historicity, see Schilbach et al., 2013). For the triangles, we had identical objects that differed only in the presence or absence of a single agent-like feature (eyes). Whatever attributes the eyes appeared to bring to the triangles on which they were affixed (triangles-with-eyes condition) lingered when the triangles were presented again without eyes (plain triangles). One argument might be that the triangles were viewed as the same triangles with and without eyes. That is, once the triangles had been imbued with potential agency, having them "return" without eyes did not immediately strip them of the attributes that were motivating the task to take on social relevance. By contrast, the fashion dolls and artists figures are clearly not the same object but are different representations of human form. Although artist figures alone may be sufficient to engage the social mechanisms that affect performance with agent-like targets, they appear to lose any attributes that convey a sense of agency when one has had experience with the more representative form of the fashion doll. Anecdotally, some participants even remarked that the artist figures seemed "creepy" after seeing the fashion dolls. This type of comment has never been noted before in our previous studies nor in the condition when the artist figures came first, suggesting that the experiential context was asserting a strong influence over the perception of the objects at a very basic level.

Although not significantly different from the cases presented here, it is notable that the artist figures in Shelton et al. (2012) had a numerically larger correlation than any of the conditions in the present study. This may be due to the fact that the artist figures were experienced in the context of two other objects that did not possess agent-like qualities (plain triangles and cameras). In 2/3 of the orders used for the study, the artist figures would have come after one or both of the object conditions, which may have magnified the correlation relative to the conditions used in the present study. The lack of order effects on the correlations in the original study is potentially problematic for this argument. However, given that the artist figures when presented first had a correlation of −0.39 in the present study it is possible that the original study was insufficiently powered to detect changes from such a high baseline correlation. Again, this suggests that the role of experiential context may be a critical factor in the way individuals engage a VSPT task with different targets.

Both the induction of agency and contextual effects noted above are driven by physical features. For example, the carryover of agency from triangles-with-eyes to plain triangles likely depended on the agency evoked by the physical features of the eyes carrying over to the highly similar plain triangles. Likewise, the many agent-like features of the fashion dolls appeared to convey agency, and the diminished agency for artist figures following experience with fashion dolls likely depended on the contrast of these "rich" agents to the highly dissimilar artist figures. However, the conveyance of agency is not limited to physical features. In Experiment 3, the performance on the VSPT task with plain triangles was again correlated with social skills when the triangles were referred to as aliens rather than triangles. Implying a being, albeit an alien being, appears to be similar to adding physical features such as eyeballs, motivating participants to engage in the task in a way that allows social skills to assert influence. This suggests that when interpreting the targets of a VSPT task, people may have a very low threshold for allowing a target to be "social."

A running theme through this work is the introductory framework in which the target and possibly other features of a VSPT task can affect whether the task itself is socially relevant or not. Using this framework, we have demonstrated that the degree to which a task appears to be social or not involves the complex interaction of target features and experiential context, which includes the presence of other targets and the language used to identify the targets. One might be tempted to conclude that this work is largely about methodology, and in some sense, this is the case. Although we have not exhaustively tested all types of targets or target combinations, our findings clearly offer some suggestions for how to craft a VSPT task that is or is not sensitive to social skill influence. For example, if one's goal is to understand VSPT in isolation, what we have termed nonsocial VSPT, then one can design a task that limits the potential agency as much as possible. However, this work also speaks to and raises many deeper theoretical issues about how the human brain processes spatial information in order to reason about the world.

A first critical point is that the sensitivity of VSPT performance to targets and experiential context is consistent with the notion that VSPT in real-world settings is not a task that happens in isolation. For example, imagine sitting in the stands at a ball game waiting for a friend. Your friend is lost, but you can see him under the scoreboard. By phone, you might give him directions based on what you know he can currently see. The particular directions you give might be influenced by a wide variety of concerns—your friends known ability to mix up left and right, the urgency with which you want to get him to the seat before first pitch, whether you want him to pass the concession stand to grab refreshments, etc. In this example, the ability to relate to the friend's situation involves both the understanding of visual-spatial perspective (what the friend can see) but also the socially relevant situational factors (the friend's state, abilities, goals). Therefore, one's performance should be dependent on the interaction of spatial and social skills such that this socially relevant VSPT situation will benefit if social skills are strong but might be hindered if they are weaker.

This still leaves the broader question of why the specific judgments participants were asked to do in our VSPT task should be influenced by social skills when targets appear to convey agency. That is, one could imagine that the ballgame example could be accomplished by having the spatial reasoning done by a "purely" spatial computational process with social skills only entering at the point of deciding how to communicate that information to an agent. Our task only requires the judgment and not a tailored communication of the outcome, suggesting that the social influence may be operating throughout the process of perspective taking. Although our results are ambivalent with respect to how the presence of an agent-like target might be altering the underlying computations, we offer some speculation about how this interaction might come about. One possibility is that VSPT involves first essentially embodying the target of the potential perspective one is attempting to assess (i.e., one is attempting to assume the target's position in order to see its viewpoint). As may be the case with spontaneous perspective taking (Tversky and Hard, 2009), a potential agent as a target may automatically induce one to consider the target's social/personality attributes. One's comfort level in understanding or appreciating these attributes may then serve to gate how readily the perspective can be assumed. For example, an individual who is more socially savvy might be able to more readily recognize the utility of a potential agent through efficient assessment of relevant attributes (e.g., the eyes on the fashion doll means she might have the ability to see) and dismissal of irrelevant and unknown attributes (e.g., she is happy and has good fashion sense), whereas an individual with less social savvy might experience inhibition in trying to take the perspective of a potential agent because he/she cannot apprehend the attributes as readily and choose those that would facilitate embodiment. By contrast, when the perspective taking involves an object as the target, there are no obvious social attributes, so one's social savvy will neither hurt nor help, as it is irrelevant.

In this working model, we do not propose different mechanisms or processes for VSPT with agents vs. objects. Instead, we are suggesting that there is a common spatial component irrespective of the target, which is consistent with the observed correlations between the different versions of the VSPT task (targets with and without agency). However, when there is an agent, social skills may act as a gateway for the initial step of embodying the target. This proposed role suggests that we will still see individual differences in the spatial aspects of the tasks, regardless of target type, but we will have additional variability due to social skills when the target is a potential agent. Whether the proposed model above or an alternative framework ultimately captures the interaction of social and spatial skills, this work motivates a deeper question: what are the advantages of having a system that is generally sensitive to the presence of agents for a seemingly spatial task given that this sensitivity can benefit some individuals and hinder others relative to non-social conditions? Is this driven by the folk wisdom that humans are simply social beings? These are open questions and ones not readily addressed empirically, but they provide fodder for thinking critically about the interactive nature of human cognition.

The overarching goal of this project was to deepen the exploration of factors that determine whether and when VSPT might be sensitive to the influence of social skills. Taken together, the results suggest that the social influence on VSPT is mediated by a complex relationship that includes the task, the target, and the context in which the target is perceived. Future studies may continue to elaborate on the various boundary conditions that evoke agency or take it away, but the broader message from our work and similar studies is the importance of thinking beyond the bounds of a single domain to explain the complexity of human behavior.

#### **ACKNOWLEDGMENTS**

We would like to thank Ben Nelligan for helpful comments on previous versions of this manuscript. Portions of this work were supported in part by a Woodrow Wilson undergraduate research fellowship that was awarded to Alexandra J. Murray.

#### **REFERENCES**

of self versus other: visual-spatial perspective taking and agency in a virtual ball-tossing game. *J. Cogn. Neurosci.* 18, 898–910. doi: 10.1162/jocn.2<IP_ADDRESS>8

**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.

*Received: 02 July 2013; accepted: 05 August 2013; published online: 05 September 2013.*

*Citation: Clements-Stephens AM, Vasiljevic K, Murray AJ and Shelton AL (2013) The role of potential agents in making spatial perspective taking social. Front. Hum. Neurosci. 7:497. doi: 10.3389/fnhum.2013.00497*

*This article was submitted to the journal Frontiers in Human Neuroscience.*

*Copyright © 2013 Clements-Stephens, Vasiljevic, Murray and Shelton. 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) or licensor 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 influence of visual perspective on the somatosensory steady-state response during pain observation

## *Dora L. Canizales1,2,3, Julien I. A. Voisin3,4, Pierre-Emmanuel Michon3, Marc-André Roy2 and Philip L. Jackson1,2,3\**

*1 École de Psychologie, Université Laval, Québec, QC, Canada*

*2 Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec, Québec, QC, Canada*

*3 Centre Interdisciplinaire de Recherche en Réadaptation et Intégration Sociale, Québec, QC, Canada*

*4 Département de Réadaptation, Université Laval, Québec, QC, Canada*

#### *Edited by:*

*Antonia Hamilton, University of Nottingham, UK*

#### *Reviewed by:*

*Cosimo Urgesi, University of Udine, Italy*

*Leonie Koban, University of Colorado Boulder, USA*

#### *\*Correspondence:*

*Philip L. Jackson, École de Psychologie, Université Laval, Pavillon Félix-Antoine-Savard, 2325, rue des Bibliothèques, Québec, QC G1V 0A6, Canada*

*e-mail<EMAIL_ADDRESS>
The observation and evaluation of other's pain activate part of the neuronal network involved in the actual experience of pain, including those regions subserving the sensoridiscriminative dimension of pain. This was largely interpreted as evidence showing that part of the painful experience can be shared vicariously. Here, we investigated the effect of the visual perspective from which other people's pain is seen on the cortical response to continuous 25 Hz non-painful somatosensory stimulation (somatosensory steady-state response: SSSR). Based on the shared representation framework, we expected firstperson visual perspective (1PP) to yield more changes in cortical activity than third-person visual perspective (3PP) during pain observation. Twenty healthy adults were instructed to rate a series of pseudo-dynamic pictures depicting hands in either painful or non-painful scenarios, presented either in 1PP (0–45◦ angle) or 3PP (180◦ angle), while changes in brain activity was measured with a 128-electode EEG system. The ratings demonstrated that the same scenarios were rated on average as more painful when observed from the 1PP than from the 3PP. As expected from previous works, the SSSR response was decreased after stimulus onset over the left caudal part of the parieto-central cortex, contralateral to the stimulation side. Moreover, the difference between the SSSR was of greater amplitude when the painful situations were presented from the 1PP compared to the 3PP. Together, these results suggest that a visuospatial congruence between the viewer and the observed scenarios is associated with both a higher subjective evaluation of pain and an increased modulation in the somatosensory representation of observed pain. These findings are discussed with regards to the potential role of visual perspective in pain communication and empathy.

**Keywords: pain observation, visual perspective, empathy, electroencephalography, somatosensory steady-state**

## **INTRODUCTION**

Seeing pain in other people is an experience susceptible to trigger responses akin those felt when we hurt ourselves. Indeed, several neuroimaging studies found a partial overlap between cerebral circuits involved during actual experience of pain (known as the pain matrix) and during the observation of other's pain (for a recent review see Fan et al., 2011; Lamm et al., 2011). More specifically, the observation of other's pain engages in a similar way some of the neuronal systems subserving the sensory (e.g., somatosensory cortices) and the affective components (e.g., insula, anterior cingulate cortex) of self pain perception (Fitzgibbon et al., 2010; Corradi-Dell'Acqua et al., 2011) . The activation of these regions suggests, indirectly, that observing pain produces a fine-grained multidimensional mental representation of the other's pain even in the absence of somatosensory input. Even though this mental representation of pain enables an observer to partially share the subjective experience of other's pain, the extent of this sharing mechanism can vary according to different factors (Coll et al., 2011). Note that the specificity of the nociceptive cerebral representation itself (signature; Wager et al., 2013) is currently being debated and the extent to which this representation also codes for the pain of others (Krishnan et al., 2013) and social pain (Iannetti et al., 2013) appears to be more limited than initially thought.

Nevertheless, recent neuroimaging studies have provided strong evidence that observation of pain can involve the somatosensory cortex, known to contribute to sensory processing of noxious stimuli (Bufalari et al., 2007; Lamm et al., 2007b; Cheng et al., 2008; Betti et al., 2009; Han et al., 2009; Yang et al., 2009; Voisin et al., 2011a). Moreover, the recruitment of sensory processes of pain is distinctly demonstrated by a decrease of the somatosensory response during pain observation (Cheng et al., 2008; Voisin et al., 2011a; Marcoux et al., 2013). Although the involvement of the sensory cerebral circuits during pain observation has been repetitively demonstrated (see Keysers et al., 2010; Lamm et al., 2011, for reviews), the variables that modulate these sensory processes remain unclear.

A growing body of evidence supports the idea that somatosensory activity is influenced by *perspective taking* (*PT*; Ruby and Decety, 2001, 2003, 2004; Jackson et al., 2006a,b) PT can be defined as the ability to adopt someone else's point of view in order to understand their situation (Decety et al., 2006). This ability represents an essential component of empathy, which refers to the faculty to understand and to share other's emotions and feelings and to respond appropriately (Decety et al., 2006). Studies generally distinguish cognitive PT, which requires the individual to imagine being the other person (e.g., Ruby and Decety, 2003; Jackson et al., 2006b; Dosch et al., 2010) from visual PT, which involves seeing a scene or a situation from different angles (e.g., Jackson et al., 2006a; Kessler and Thomson, 2010). Regarding cognitive PT, several studies demonstrated that thinking about oneself in a specific situation generates different behavioral and cerebral responses than imagining another person in the same situation (Ruby and Decety, 2004; Jackson et al., 2005, 2006b; Lamm et al., 2007a, 2008; Li and Han, 2010) While self-perspective requires fast and automatic processes, which are more related to agency (i.e., ability to attribute the origin of an action), adopting the perspective of others appears to engage more deliberate and regulatory mechanisms (van der Heiden et al., 2013).

Visual PT generally results from a mental rotation of one's own perspective toward the other's perspective in order to consider the spatial information from the other's viewpoint that may be different from the subject's one (Kozhevnikov and Hegarty, 2001; Kessler and Thomson, 2010). Visual PT provides crucial spatial information that enables a person to appropriately conduct social interaction and understand other's mental states (Langdon and Coltheart, 2001; Kaiser et al., 2008; Lambrey et al., 2008; Kessler and Thomson, 2010). The manipulation of the visual perspective is broadly used in cinematography (e.g., subjective/objective camera), particularly in horror movies and video games (e.g., first/third-person games) in order to generate the feeling in the spectator of sharing the point of view of the character.

Behavioral studies generally report faster reaction time and increased accuracy performance when an object or an action is seen in a *first-person* visual perspective (1PP) (i.e., seeing a situation from the onlooker's viewpoint) compared to a *thirdperson* visual perspective (3PP) (i.e., seeing a situation presented in someone else's viewpoint) (Jackson et al., 2006a; Kaiser et al., 2008). Jackson et al. (2006a) demonstrated that seeing or imitating actions performed in the 1PP yielded stronger sensorimotor activation in comparison to the 3PP. This supports the assumption that adopting 1PP generates more robust sensorimotor representation of the action in the onlooker's brain that may be close to actual execution of the action. 3PP also seems to involve specific neuronal processes associated with spatial transformations (Jackson et al., 2006a; Kaiser et al., 2008; Callan et al., 2012), visual motion perception (Bundo et al., 2000; de Lussanet et al., 2008), and executive functions such as inhibition and attention (Hampshire et al., 2010; Dodds et al., 2011). Altogether, these findings show that adopting 1PP and 3PP requires distinct neuronal processes: the former may be more associated with automatic embodiment (resonance) and the latter with cognitive functions such as visuospatial processing and inhibition.