Anthro Ph.D. Student Documents "Deceit" Amongst Monkeys

Stony Brook, N.Y. – A common feature that distinguishes humans from other animals is our ability to role play. The cognitive ability to “take the role of the other,” to use sociologist/philosopher George Mead’s term, allows us to predict how others will respond to our personal behavior because we can put ourselves in others shoes. In others words, if I’m in a job interview and I see my interviewer reacting to me in a particular way (frowning perhaps), I could ask myself: If I was in his/her position and I frowned, what would I be thinking? Making conclusions about the interviewer’s act (by taking his/her role), and then reacting to that act is a distinctly human trait.

Perhaps.

A capuchin monkey

A recent article published in Proceedings of the Royal Society B by Stony Brook anthropology graduate student Brandon Wheeler may challenge this theory. While studying capuchin monkeys in Iguazú National Park in Argentina, Brandon noticed that some monkeys may have been tricking others to steal their food, implying perhaps that they understood how others reacted to their own behavior.

Tufted capuchin monkeys are small primates that, when feeling threatened by predators, give off warning calls that sound like hiccups to alert other members of the group of impending danger. The other monkeys in the group will then flee or become more alert.

Brandon did an experiment where he placed banana pieces on small feeding platforms. He found that low-ranking members of the group (those who usually were prevented by higher-ranking members from accessing the food), used the danger call many times when no real danger existed. The higher-ranking members would often flee, and the deceptive callers would take this chance to acquire the food that was left for them. In this sense, the lower-ranking monkeys acted as if they knew that the others would flee based on their knowledge that these calls represented danger to them.

Brandon Wheeler

However, it is unclear whether the “deceitful” monkeys were doing this intentionally (implying that they do indeed role play), or that this behavior is actually “functional deception.” For instance, capuchins produce these calls when stressed, and feeding periods are probably stressful for the low rankers, and this may explain the behavior that Brandon noticed in his experiment. Low-ranking monkeys may then learn to associate hiccupping with being fed. This phenomenon does not imply that the monkeys actually understand that they are creating false belief. The deceit may be an accidental byproduct.

Despite the lack of evidence to answer this crucial question, Brandon’s paper has generated a significant amount of interest in the scientific community. Articles have been published online in The Scientist, Science Now, National Geographic News and a dozen or so popular science publications.

Brandon has successfully defended his dissertation entitled “An Experimental Analysis of Alarm Calling Behavior in Wild Tufted Capuchin Monkeys (Cebus apella nigritus).” He will graduate in August.

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