 21. Emotion and Personality  455
Expressions of emotion coordinate social 
interactions in at least three general ways 
(Keltner & Kring, 1998; van Kleef, 2016). 
First, through their informative function,  
emotional expressions provide rapid infor -
mation not only about the sender’s current 
emotions but also about that individual’s in -
tentions and relationship with the perceiver 
(Ekman, 1993; Fridlund, 1992). In this way, 
expressions of emotion situate people in spe -
cific relationships. For example, anger clearly 
communicates strength and dominance vis-
à-vis interaction partners (Knutson, 1996). 
When individuals express anger in the face 
or voice, they are perceived to have more 
power and are more likely to get their way 
in negotiations (van Kleef, De Dreu, Pietro -
ni, & Manstead, 2006). From brief laughs 
as well, observers can infer an individual’s 
rank within a social hierarchy, as well as af -
filiative intent; acoustic properties of laughs 
signal social standing and friendly inten -
tions (Oveis, Spectre, Smith, Liu, & Keltner, 
2016; Wood, Martin, & Niedenthal, 2017). 
Emotional expressions also carry informa -
tion about the sincerity of the sender’s inten -
tions. For example, Krumhuber, Manstead, 
and Kappas (2007) found that people trust 
interaction partners more and will give more 
resources to those partners who display au -
thentic smiles (which have longer onset and 
offset times) rather than fake smiles. Emo -
tional expressions convey information about 
the environment as well, allowing individu -
als to coordinate their responses to outside 
opportunities or threats (e.g., Klinnert, 
Emde, Butterfield, & Campos, 1986; Sorce, 
Emde, Campos, & Klinnert, 1985). For ex -
ample, parents use touch and voice to signal 
to their young children whether other people 
and objects in the environment are safe or 
dangerous (Hertenstein & Campos, 2004).
Second, emotional expressions coordinate 
social interactions through their evocative 
function,  triggering specific responses in 
perceivers. For example, early in the study 
of facial expression, researchers found that 
warm smiles evoke calmer peripheral physi -
ology in interaction partners, whereas angry 
facial expressions tend to trigger stress- 
related peripheral physiology and increased 
activation in the amygdala—  a neural struc -
ture preferentially engaged by threat-  related 
information (Esteves, Dimberg, & Öhman, 1994; Lieberman et al., 2007). Consider also 
the powerful reactions a baby’s cry produces 
in caregivers nearby. Infant crying includes 
a long, continuous sound accompanied by 
acoustic variations that signal distinct states, 
including anger (when the infant’s hands are 
pinned down), pain (after getting a shot), or 
fear (upon hearing a loud sound) (Chóliz, 
Fernández-  Abascal, & Martínez-Sánchez, 
2012). Within 49 milliseconds (a 20th of 
a second) of hearing a human infant’s cry, 
adults show activation in the periaqueductal 
gray region of the brain—  associated with 
sympathy and caregiving behavior, as well as 
management of one’s own pain—but this is 
not seen in response to animal cries, human 
adult sounds, and other controls (Parsons et 
al., 2014). Similarly motivated researchers 
have documented the specific behaviors that 
emotional expressions evoke in perceivers. 
In social referencing, for example, a parent’s 
facial expression of fear will deter an infant 
from crawling across a transparent glass 
cliff, and a disgust expression in the voice 
(“Yuck!”) prompts the child to avoid play -
ing with the referred-  to toy (Hertenstein & 
Campos, 2004). Brief displays of embarrass -
ment have been shown to prompt affiliative 
feeling, cooperative intent, and forgiveness 
in observers (Feinberg et al., 2012).
Finally, emotional displays serve incen -
tive functions,  inviting and rewarding oth -
ers’ behavior. Warm smiles and touches are 
often used by parents to promote desired 
behaviors in their children, thus increasing 
the probability of those behaviors occurring 
in the future (e.g., Tronick, 1989). Laughter 
from interaction partners also rewards desir -
able social behavior in adults (Bachorowski 
& Owren, 2001).
Fleeting emotion-  related patterns of fa -
cial muscle movements, vocalization, touch, 
posture, and gaze are much more than read -
outs of interior states; emotional expressions 
initiate a cascade of responses from social 
partners that provide structure to ongoing 
interactions (Oatley, 2009). Distress vocal -
izations evoke patterns of sympathy and 
compassion that, in turn, promote attach -
ment formation. Smiles and laughter set 
the stage for affiliative exchanges, coopera -
tion, and friendship. Expressions of anger, 
pride, and contempt nonverbally communi -
cate rank and situate individuals within the 