Have you ever wondered why yawning is so contagious? One moment you may be sitting at the dinner table with your friend as they let out a big yawn, and the next second you are doing the same. This involuntary action is something that is commonly seen in humans, and it seems to be common in mammals too.
Emotional contagion is the idea allowing individuals to experience the same emotions as another individual. This emotional contagion can also be linked to facial mimicry. Facial mimicry is when facial displays are involuntarily copied by others (Ross et al. 2008). The example of yawning is similar to smiling and laughter; humans often mimic these actions when observing them through social engagement. Although there are few studies on emotional contagion and facial mimicry as it applies to non-humans, primates are one of the few that have been observed to clearly exhibit this behavior.
Researchers came together to study this unfamiliar aspect of primate emotion and behavior and looked at a specific example in Orangutans (Pongo pygmaeus). This type of involuntary behavior was labeled as rapid involuntary facial mimicry and involved one orangutan presenting a facial expression and the social partner exhibiting the same expression. The orangutans were observed during their everyday play and more specifically, when giving an open-mouthed facial expression (OMF) which is common during play among individuals. These open-mouthed facial expressions were determined to be comparable to human laughter (Ross et al. 2008).
Four hundred and thirty two play bouts were observed among 31 orangutans, ranging from two to 12 years of age. Different play actions and intensities were recorded for each interaction. Each facial display at or within 1 second of the other playmate’s expression was assessed. Two individuals were observed together and individual 1 either produced an OMF or a neutral expression. In each interaction, individual 2, who was reacting to individual 1, was recorded to produce four different possible reactions; a congruent reaction which was when an OMF was produced in response to individual 1’s OMF and a neutral expression was produced in response to individual 1’s neutral expression; a non-congruent reaction which was when an OMF was produced in response to individual 1’s neutral expression, and a neutral expression was produced in response to individual 1’s OMF; the two other reactions were always displaying OMFs or never displaying OMFs. There were two age groups of orangutans, infants below 4 years of age and adolescents 4 years of age and older. There were also two classes of age differences studied, less than two years apart and equal to or more than two years apart.
After watching many play interactions, the researchers determined that the orangutans more often produced OMFs when their social partner produced an OMF, and that reacting individuals more frequently produced reactions mimicking their social partner. Although this trend was more significant for juveniles and adolescents and playmates that were 2 or more years apart, the trend of mimicry was still present for infants and playmates with less age difference.
Orangutans in this study were seen to exhibit rapid facial mimicry, similar to what humans often experience on a daily basis. The rapid facial mimicry was seen in orangutans mimicking a common facial expression during play, or an open-mouthed face. Although the majority of individuals did exhibit evidence of rapid facial mimicry, there was still 36% that did not rapidly emit OMFs directly after observing an OMF in a social partner. In humans, we are more likely to mimic a smile from a friend rather than a stranger, so it is possible that in orangutans, facial expressions during play may be mimicked more often for closer individuals rather than strangers (Ross et al. 2008).
These similarities between orangutans and humans in regards to involuntary facial mimicry indicates that this behavior may have evolved prior to humans and may even be applicable to other mammals, which is subject to further investigation.
Davila Ross, M., Menzler, S., & Zimmermann, E. (2008). Rapid facial mimicry in orangutan play. Biology letters, 4(1), 27–30.
https://doi.org/10.1098/rsbl.2007.0535
