In a new study published in Evolution and Human Behavior, researchers found that people who displayed more nonverbal stress behaviors were rated as more likeable. People who had more social connections were more accurate in detecting stress in others.
Across species, organisms show signs of stress that can be detected by others. From an  evolutionary perspective, little is known about the adaptive advantage of displaying signs of stress. Stress behaviors, also known as displacement behaviors, include self-grooming, face-touching, head scratching, and fidgeting with objects, all of which may help someone regulate their stress. Researchers Jamie Whitehouse and colleagues were interested in investigating whether displacement behaviors are reliable indicators of stress in humans.
“We wanted to find out what advantages there might be in signaling stress to others, to help explain why stress behaviors have evolved in humans,” explained Whitehouse in a news release.
“If producing these behaviors leads to positive social interactions from others who want to help, rather than negative social interactions from those who want to compete with you, then these behaviors are likely to be selected in the evolutionary process. We are a highly cooperative species compared to many other animals, and this could be why behaviors which communicate weakness were able to evolve.”
For their study, Whitehouse and colleagues recruited 31 participants who responded to pre-task questionnaires, provided saliva samples, participated in a stress-inducing task (the Trier-Social Stress Test), gave a post-task salivary sample, and filled out a post-task questionnaire. More than 100 other participants were recruited to act as raters. These participants filled out the Social Network Index questionnaire to assess social connection and the Berkley expressivity questionnaire to assess emotional expressivity. These participants also watched 10 stimuli videos to estimate how stressed individuals were and rated how much they liked the person.
Results of this study show that self-reported stress was positively associated with the raters’ rating of their stress. The ratings of stress were positively correlated with the proportion of displacement behaviors but negatively associated with the proportion and duration of submissive behaviors. People who performed more displacement behaviors were rated as more likeable. Cortisol levels from the saliva samples were not associated with self-reported stress, average stress ratings, or any other measures.
Displacement behaviors appear to mediate the relationship between self-reported stress and average ratings of stress. There was little difference in displacement behaviors and rating between males and females; however, female actors were rated as slightly more likable.
Whitehouse and colleagues said that these findings provide evidence that stress (displacement) behaviors influence the perception of how likeable a person is. Their results also show that one’s ability to accurately rate other’s level of stress predicted the size of their social network. People who made more errors in rating levels of stress typically had a smaller social network and those who made less errors had larger social networks. However, raters who were most accurate reported having fewer social connections. Whitehouse and colleagues argued that being too accurate at reading the motivations of others may not be a desirable characteristic in a social partner.
Based on their findings, Whitehouse and colleagues noted that there are specific behaviors of stress that raters used to determine the other person’s level of stress, but the specific behaviors were not able to be determined. This study also shows that displacement behaviors are a means of communicating stress to others; however, the exact information that is being communicated is unknown.
Whitehouse and colleagues said that displacement behaviors could be adaptive by allowing other to anticipate their future behavior or to signal to others that their behavior is unpredictable, since stress-related behaviors are related to risk-taking behaviors. Individuals who displayed less displacement behaviors may have been rated as less stressed because the raters perceived they had more established relationships. Those who were more stressed may have been rated as more likeable because they are perceived to be more cooperative and are potential social partners.
“If the individuals are inducing an empathetic-like response in the raters, they may appear more likeable because of this, or it could be that an honest signal of weakness may represent an example of benign intent and/or a willingness to engage in a cooperative rather than competitive interaction, something which could be a ‘likable’ or preferred trait in a social partner,” co-author Bridget Waller said in a news release. “This fits with current understanding of expressivity, which tends to suggest that people who are more ’emotionally expressive’ are more well-liked by others and have more positive social interactions.”
The study, “Signal value of stress behaviour“, was authored by Jamie Whitehouse, Sophie J. Milward, Matthew O. Parker, Eithne Kavanagh, and Bridget M. Waller.
