Written by Melinda Wenner Moyer for Scientific American

There’s a reason your mother told you to look people in the eye when you talk to them: eye contact conveys important social cues. Yet when someone holds your gaze for more than a few seconds, the experience can take on a different tenor. New work elucidates the factors that affect whether we like or loathe locking eyes for a lengthy period.

Researchers have long known that eye contact is an important social signal. Our recognition of its import may even be hardwired. One study found that five-day-old babies prefer looking at faces that make direct eye contact compared with faces that have an averted gaze. “Eye contact provides some of the strongest information during a social interaction,” explains James Wirth, a social psychologist now at Ohio State University at Newark, because it conveys details about emotions and intentions. (Lack of eye contact is one of the early signs of autism in infants and toddlers.) The power of eye contact is so great that, according to a 2010 study co-authored by Wirth, if someone avoids your gaze for even a short period, you may feel ostracized.

But what determines how we feel about prolonged eye contact? One recent study explored this question. In research presented in May 2015 at the Vision Sciences Society conference, psychologist Alan Johnston and his colleagues at University College London collected information from more than 400 volunteers about their personalities. Then the subjects indicated their comfort level while watching video clips of actors who appeared to be looking directly at them for varying lengths of time.

Johnston and his colleagues found that, on average, the subjects liked the actors to make eye contact with them for 3.2 seconds, but the subjects were comfortable with a longer duration if they felt the actors looked trustworthy as opposed to threatening. “Gaze conveys that you are an object of interest, and interest is linked to intention,” Johnston explains—so if someone appears threatening and holds your gaze, that could indicate that the person has bad intentions. This idea could help explain findings from a controversial study published in 2013, which reported that people are more likely to change their views on a political issue when they are being challenged by people who do not make eye contact with them. If the challengers had made eye contact, they might have seemed more threatening and less trustworthy.

Our reaction to prolonged eye contact may relate to how we perceive ourselves, too. Johnston and his colleagues found that the more cooperative and warm subjects believed themselves to be, the longer they liked eye contact to be held. Johnston speculates that the more socially comfortable a person feels, the more he or she may “enjoy the intimacy of mutual gaze.”

For more on eye contact and detecting deception, view this past blog.

Social interactions among bonobos – pointing gestures and pantomime, too, are deployed in communication. Credit: LuiKotale Bonobo Project/ Zana Clay

Pointing and pantomime are important components of human communication but so far evidence for referential communication in animals is limited. Observations made by researchers Pamela Heidi Douglas and Liza Moscovice of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, make important contributions to this research topic: To solve social conflicts female bonobos invite other females to engage in a socio-sexual behaviour by using pointing gestures and mimicking hip swings. This observation raises new questions about the evolution of referential communication and human language.

One important feature of human language is the ability to use arbitrary vocal and gestural signals to symbolically represent or refer to objects, actions or events. Two examples of symbolic gestural communication are pointing, which directs someone else’s attention to an external object in the environment, and pantomime, or acting out parts of actions to communicate desires or goals even in the absence of the relevant objects.

It has long been believed that forms of referential gesturing, such as pointing, and forms of iconic gesturing, such as pantomime, are unique to humans. In a recent study of wild bonobos at the Luikotale field site in the Democratic Republic of Congo, researchers from the Max Planck Institute for Evolutionary Anthropology documented regular use of a form of pointing and pantomime. During their three-year study, Pamela Heidi Douglas and Liza Moscovice observed that the gestures were always produced in the context of socio-sexual behaviour between females. Female sexual behaviour serves to reduce social tension and promote cooperation. The gestures used by the females are notable in that they appear to be not only intentional, but also referential and potentially iconic, since they communicate specific information about the desired goal.

The majority of gestures occurred in feeding contexts, and led to socio-sexual interactions between the gesturer and the recipient. Following socio-sexual interactions, the gesturer and partner were more likely to stay near each other and to feed together compared with rare situations when females rejected the gestural requests for sexual interactions. This suggests that female bonobos use referential and iconic gesturing to enhance communication in contexts in which behavioural coordination and cooperation are necessary.

The observed gestures have obvious parallels with human pointing and pantomime in both form and function and the results of this research, published in Scientific Reports, challenge the current view that such gestures are unique to humans. What remains to be explored is whether bonobos have mental representations when they produce these gestures, and whether females who respond to gestures understand the referential or iconic content of the signals.