Sunday, September 22, 2019

Third-Party Punishment in Nonhuman Primates? The Tomasello-de Waal Debate

                                               Frans de Waal on "Moral Behavior in Animals"

If the morality of third-party punishment is part of our evolved human nature, as indicated in the previous post, then we might ask whether this is also found in our closest evolutionary relatives--chimpanzees and other primates.  Among primatologists, there is disagreement about this.  Michael Tomasello and his colleagues argue that there is no third-party punishment in chimpanzees (Riedl et al. 2012).  But Frans de Waal and his colleagues argue that in fact chimpanzees and other primates (such as pigtailed macaques) do show third-party punishment (Flack et al. 2005; Flack et al. 2006; von Rohr et al. 2012; Suchak et al. 2016).  This is part of a more general debate in which Tomasello tends to emphasize human uniqueness compared with other primates, while de Waal tends to emphasize the similarities between human beings and other primates.  (I have written about this debate herehere, and here.)

In his first--and most popular--book Chimpanzee Politics, de Waal described the Machiavellian politics that he observed in the chimpanzee colony at Burgers' Zoo in Arnhem, the Netherlands.  In the summer of 1976, he saw the overthrow of Yeroen, who had been the alpha male, by Luit.  A few weeks after becoming the new alpha male, Luit adopted a policy that would make him "the champion of peace and security" and thus win the support of the females and the children to strengthen his position against his male rivals for dominance.  Whenever a fight broke out among the chimps, Luit intervened to restore the peace.  Sometimes he would intervene impartially, not favoring one side over the other, but forcing the two sides apart and hitting anyone who tried to continue the fight.  At other times, he intervened to support the weaker party against the stronger--helping the lower ranking individual against the higher ranking individual who would normally win the fight.  De Waal called this the "control role" of the alpha male (1982, 124-25).  He thought the control role of the alpha male was "not so much a favor as a duty," because his position depended on keeping the peace and protecting the females and the children from attack so that they will help him in repulsing his male rivals.

In his later writings, de Waal has identified the "control role" as "policing"--intervening impartially to control conflict.  This term "policing" was first used by biologists studying social insects as the term for how insects monitor behavior and suppress conflict through impartial enforcement of norms by bystanders.  (I have written about the "bee police" here.)

                                                "The Surprising Science of Alpha Males"

Against de Waal's claims, Tomasello and his colleagues have asserted that de Waal has not presented any direct tests of third party punishment of violations of cooperation among chimpanzees or other primates.  In 2012, they reported their own experimental study in which 13 captive chimpanzees were presented with an opportunity to engage in third-party punishment, but they failed to do so (Riedl et al. 2012).  Three chimpanzees occupied three separate cages designated as "victim," "thief," and "actor."  A tray of food was in front of the victim's cage.  The thief could pull a rope to drag the tray towards his own cage and thus steal the food.  While observing this theft, the actor could pull a rope or press a button to collapse the food tray into a box out of reach of the chimpanzees.  The actor was either dominant over the thief or subordinate to the thief.  But in neither case did the actor punish the thief for stealing the food from the victim.  However, in a test of second-party punishment, where the thief stole food from the actor, and the actor was dominant over the thief, the actor did punish the thief.  This seemed to show that chimpanzee punishment is restricted to retaliation against personal harm, when the punisher is in a position of dominance.

De Waal and his colleagues insist that they have observed third-party policing, or intervening impartially to control conflict, in captive groups of pigtailed macaques and chimpanzees (Flack et al. 2005; von Rohr et al. 2012).  They do concede, however, that this is one of the rarest forms of conflict management among primates, and that most of the policing interventions that do occur are carried out by a few dominant individuals.

De Waal suggests that Tomasello's failure to see third-party punishment in his experiment arose from his limited laboratory setting in which two or three apes were brought into a very contrived situation.  De Waal describes his own experimental setting that mimics natural conditions in which many individuals have an open choice for cooperation, competition, and enforcement mechanisms (Suchak et al. 2016).  A group of 11 captive chimpanzees was put before a pulling apparatus where two or three individuals were required to pull together to obtain a food reward.  The experiment took place in 94 one hour sessions--occurring two to three times per week--that were videotaped.  During these sessions, the chimpanzees could pull jointly at the apparatus to obtain the reward, and this would be counted as a cooperative act.  They were also free to engage in competitive acts--freeloading (stealing the reward without pulling), displacement (taking someone's place at the apparatus), or fighting.

The cooperative pulling experiment was originally designed by Meredith Crawford in 1937 to test for cooperation among chimpanzees.  Since then, many different species of animals have been tested with cooperative pulling experiments.  The Wikipedia article on this is good.

Over the 94 hours of de Waal's experiment, there were a total of more than 600 competitive interactions (freeloading, displacement, or fighting) and 3,565 cooperative interactions--an average of one cooperative act every 2 minutes.  The rate of cooperation versus competition fluctuated over the 94 hours--starting with high cooperation then dropping to more competitive interactions and finally rising to almost complete cooperation at the end.

There were 175 attempts at freeloading, and 91 were successful (63%).  Most of the punishment for freeloading was second-party punishment--that is, the victim of freeloading retaliated against the freeloader.  Third-party outsiders intervened to punish freeloaders only 14 times (8% of the freeloading events).  Four of these third-party interventions were impartial or policing interventions, in which a dominant chimp intervened to stop a fight between a freeloader and a victim of freeloading.  In nine of the 10 partial interventions, the intervening dominant individual favored the victim of freeloading over the freeloader.  So third-party punishment did occur, but it was quite rare.

The primary means for enforcing cooperation was not direct punishment but partner choice.  Victims of freeloading or displacement chose to withdraw from the freeloading and displacing individuals, and then they sought out individuals of similar rank who could be counted on to cooperate.  Partner choice can be seen as indirect punishment or indirect reciprocity, in which individuals cooperate with those who have a reputation for being cooperative.

The rarity of the third-party punishment seen by de Waal and his colleagues might explain why Tomasello and his colleagues have not seen this at all.  This also suggests that nonhuman primates show only the evolutionary precursors or building blocks for the fully developed third-party punishment practiced by human beings.


de Waal, Frans.  1982. Chimpanzee Politics: Power and Sex Among Apes. New York: Harper and Row.

Flack, Jessica, Frans de Waal, and David Krakauer. 2005. "Social Structure, Robustness, and Policing Cost in a Cognitively Sophisticated Species." The American Naturalist 165: E126-E139.

Flack, Jessica, Michelle Girvan, Frans de Waal, and David Krakauer. 2006. "Policing Stabilizes Construction of Social Niches in Primates." Nature 439: 426-429.

Reidl, Katrin, Keith Jensen, Josep Call, and Michael Tomasello. 2012. "No Third-Party Punishment in Chimpanzees." Proceedings of the National Academy of Science 109: 14824-14829.

Suchak, Malini, Timothy Eppley, Matthew Campbell, Rebecca Feldman, Luke Quarles, and Frans de Waal. 2016. "How Chimpanzees Cooperate in a Competitive World." Proceedings of the National Academy of Science 113: 10215-10220.

von Rohr, Claudia Rudolf, Sonja Koski, Judith Burkart, Clare Caws, Orlaith Fraser,  Angela Ziltener, Carel van Schaik. 2012. "Impartial Third-Party Interventions in Captive Chimpanzees: A Reflection of Community Concern." PLoS ONE 7: e32494.

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