The Three Stooges was the source of an ongoing controversy between my parents. My dad introduced my brother and me to their antics and would often laugh along with us as we imitated their physical hijinks in front of the TV. But, for my mom, the Stooges’ fake violence and prat falls were simply ridiculous and she worried that the physical play it was encouraging would lead to fights where one of us would get hurt. She preferred we watch Laurel and Hardy.

"Let boys be boys," was my dad's usual response. He would only intervene if things got out of hand. My mother lost that argument and, throughout our childhood, was noticeably disappointed every time she heard one of us say, “Nyuk, nyuk, nyuk” after bonking the other on the head (it was usually me). "Oh, a wise guy, eh?" my brother mimicked and quickly gave chase.

But which one of my parents was right, and is there a way to find out? As it happens rough-and-tumble play is not limited to the human species and understanding why nonhuman animals engage in such behavior is a serious undertaking, one that researchers have recently come to some intriguing conclusions about.

"Social play may have an important role in establishing and maintaining relationships among animals likely to interact with each other in the future," says primatologist Elisabetta Palagi, professor of Ethology, Ecology and Evolution at the University of Pisa in Italy. According to this "social skills hypothesis," play behavior serves an adaptive function and helps individual animals test the boundaries of their social relationships and learn what is (and is not) appropriate behavior. In her research on play behavior in bonobos she found that it would increase significantly just before a period of stress, such as during feeding. Her interpretation was that play behavior diffused the tension so that aggression was less likely.

"Bonobos anticipate the forthcoming tension associated with feeding by increasing their rates of social play," she says, "thus making the foraging peaceful." Of course, having witnessed this myself, it doesn't always look peaceful.

It was already stifling at 9 o'clock in the morning and I was frantically taking notes on what I was witnessing through my field glasses. Without warning a black, hairy arm reached out to smack an unsuspecting victim, immediately giving way to a frantic chase that roused the entire troop. With his lower teeth bared, the muscular ape bared down on his assailant amidst high-pitched screams of excitement before a resounding smack reverberated beneath the canopy and signaled the end to hostilities. Having reciprocated the attack the young bonobo I had come to know as Aaron then calmly moved away, leaving Jumanji to rub his shoulder and stare at the ground in a way that, if he were human, would be interpreted as nursing a bruised ego. However, as expected, not fifteen minutes would pass before Jumanji was at it again, sneaking up on his older and stronger playmate to tag him and begin the chase anew. Once I got used to this daily routine I realized that I could have been watching Moe and Curley (with a bit more hair) taking shots at each other in the spirit of goodnatured one-upmanship.

The same behavior I witnessed during my bonobo field research is a common pattern among great apes as a whole. Seemingly identical to the children's game of tag, one individual smacks another and then runs away only to reverse the chase once they have been "tagged" themselves. More recent research with gorillas has found identical play behavior and proposes that these great apes are utilizing this game as a way to both challenge inequality and learn important social lessons.

Video of one chase bout taken by Marina Ross at Zoo Zürich in Switzerland.

Courtesy of Discovery News.

Writing in the Royal Society journal Biology Letters, researchers Edwin Van Leeuwen, Elke Zimmermann, and Marina Davila Ross have shown that gorillas demonstrate an understanding of inequality that they use to modify their behavior under changing social conditions. Rather than my few isolated examples witnessed in a single troop, Van Leeuwen and colleagues have surveyed 86 bouts taking place among six different social groups of gorillas. Furthermore, in their analysis of the data there were several remarkable consistencies that popped up over and over again.

In more than 85% of the play bouts it was the tagger who made the first move to run as well as the one who ran away. This suggests that there was an implicit understanding that the act of tagging resulted in an unequal relationship and that a response from the individual tagged would therefore be expected. In this way, play teaches important social lessons about fairness and how to respond in a social group.

"Play allows gorillas to improve their physical and social skills and to learn about their social partners," Dr. Ross said.

It may also be that an understanding of inequality is what motivates the tagger in the first place. Not only were gorillas lower in the social hierarchy the usual taggers, but they were twice as likely to tag again than were those who were more dominant. This suggests that the game served as a way to challenge inequality and push the envelope as they developed their social behavior within the group as a whole. Furthermore, by learning these lessons through play it serves to avoid the kind of costly aggression that such direct challenges have in adults.

Previous work with great apes has shown that they have the cognitive capacity for this kind of understanding about inequality and fairness. Research published last year by Sarah Brosnan showed that chimpanzees will refuse to accept a food reward if the treats were distributed unfairly, even among those who stood to benefit. This refusal to cooperate when faced with an unequal distribution of resources may have its social parallel in these games of tag. By challenging hierarchical boundaries these juveniles are learning the skills that will serve them as adults, behavior that would ultimately be fitness enhancing.

The games our children play often prepare them for the complex social skills they will need as adults, and it would seem we are not alone among the apes in this regard. Considering the attention and effort that children put into determining fairness in their social play, it should not be surprising if the moral lessons gained from these actions were also being learned in our ape cousins.

The rough-and-tumble comedy of The Three Stooges may have seemed like an encouragement of violence for my mother, but whether Howard, Fine, and Howard realized it or not they were simply making jokes out of what young apes engage in on a daily basis. By challenging one another (and the high society who was so frequently the butt of their jokes) they were challenging inequality so that, in the end, they were all equally ridiculous.

Scene from The Three Stooges, "In the Sweet Pie and Pie" (1941)

Distributed by Columbia Pictures (now in the public domain)


Van Leeuwen, E., Zimmermann, E., & Ross, M. (2011). Responding to inequities: gorillas try to maintain their competitive advantage during play fights, Biology Letters 7 (1), 39-42. DOI: 10.1098/rsbl.2010.0482

Palagi, E. (2006). Social play in bonobos (Pan paniscus) and chimpanzees (Pan troglodytes): Implications for natural social systems and interindividual relationships, American Journal of Physical Anthropology 129 (3), 418–426. DOI: 10.1002/ajpa.20289

An earlier version of this post appeared at Wired.