Yawning is a common phenomenon among vertebrates. Despite its widespread occurrence, the function of yawning remains a mystery 1. Indeed, yawning has been suggested as (i) a cooling mechanism for the brain to maintain cognitive function; (ii) a communicative behavior to indicate drowsiness or stress; (iii) a way to maintain vigilance/promote alertness among animals 2. Furthermore, contagious yawning (when observing, thinking, and/or hearing yawning induces yawning behavior in another individual) has been linked to individual differences in theory of mind tasks and self-facial recognition among humans 1. This research suggests that the yawning contagion is associated with the ability to attribute mental states to others (and possibly empathy). Among non-human mammals, contagious yawning has been demonstrated in chimpanzees (Pan troglodytes), stump-tailed macaques (Macaca arctoides), and domestic dogs (Canis familiaris) 2-5.
Recent research published in PNAS demonstrates that my study species—the gelada baboon (Theropithecus gelada)—exhibits contagious yawning2. Perhaps even more interesting, the researchers demonstrate that the strength of social relationships (not spatial proximity) is correlated with the contagiousness of yawning (i.e. more two individuals groomed, the more likely there were to respond to each other’s yawn)2. Females matched yawning types (covered teeth, uncovered teeth, and uncovered gums) more often than males; and yawning contagion was unrelated to stressful events2.
Despite these findings, several questions remain. First, I am dubious of the team’s data analysis. To determine whether or not yawning is contagious in geladas, the researchers compared a test condition (frequency of yawning for animal X given animal Y yawns) with a control condition (frequency of yawning for animal X in absence of yawning stimulus by another animal) 2. This analysis ignores the non-responsiveness of animals that are equally exposed to the yawning stimulus of animal Y. Additionally, humans are the only species where a link between mental state attribution and sensitivity to the yawning contagion is demonstrated 1. If one behavior (contagious yawning) is found in another species, this does not (by default) imply that that species is capable of mental state attribution and/or empathy. Indeed, the function of a yawning contagion may not a building block of full-blown empathy, but instead part of a different system of social behavior.
Regardless, these findings are certainly interesting. Gelada social relationships and (especially) social cognition remain understudied. However, I’m pretty sure we’ll be learning much more about our ‘bleeding-heart’ friends in the coming months.
1. Platek, S. M., Critton, S. R., Myers, T. E. & Gallup, G. G. Contagious yawning: the role of self-awareness and mental state attribution. Cognitive Brain Research 17, 223-227 (2003).
2. Palagi, E., Leone, A., Mancini, G. & Ferrari, P. F. Contagious yawning in gelada baboons as a possible expression of empathy. Proc Natl Acad Sci U S A (2009).
3. Anderson, J. R., Myowa-Yamakoshi, M. & Matsuzawa, T. Contagious yawning in chimpanzees. Proc Biol Sci 271 Suppl 6, S468-S470 (2004).
4. Joly-Mascheroni, R. M., Senju, A. & Shepherd, A. J. Dogs catch human yawns. Biol Lett 4, 446-448 (2008).
5. Paukner, A. & Anderson, J. R. Video-induced yawning in stumptail macaques (Macaca arctoides). Biol Lett 2, 36-38 (2006).
Filed under: Animal Behavior, Animal Cognition, Primatology | Tagged: empathy, gelada, yawning
Very interesting post!
I thing I wanna add though, don’t geladas “yawn” to express aggression (when they show their canines)?
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Yes, male geladas and other primates often yawn to show off their rather large canines. Interestingly, this study did not show a ‘matched response’ among males (females only). In my experiences, leader males often yawn when they are nervous and/or anxious (in the presence of rival ‘bachelor’ males) and bachelor males tend to yawn in similar behavioral states (after chasing/fighting with leader males). These yawns may or may not be vocalized, thus adding another dimension of variation to the behavior. In this study, they only looked a non-vocalized yawns.
That’s really interesting… yawning contagion isn’t exactly an indication of empathy, but my understanding is that the contagious yawning in humans is associated with the firing of mirror neurons, which underlie empathy…. thus, if other primates “catch” yawns, this would suggest that they also have mirror neurons, and thus have some of the neural structures involved in empathy… thus perhaps some neural capability for it…
I do think that the multiple functions of yawns (ie, when tired, as a threat, etc) makes this a bit more confusing… I wonder if self-directed behaviors, like scratching, is also contagious… I would think it would be…
anyway, interesting post!