Natural Rationality | decision-making in the economy of nature


The reciprocal rat

Research on reciprocity classically identified three cooperation mechanisms: 
  • kin reciprocity (A helps B because A and B are genetically related)
  • direct reciprocity (A helps B because B has helped A before--"tit for tat")
  • indirect reciprocity (A helps B because B has helped C before)
Recently, many suggested that we should also add a stronger type of reciprocity called, well,  "Strong reciprocity". Strong reciprocators cooperate with cooperators, do not cooperate with cheaters, and are ready to punish cheaters even at a cost to themselves. Strong reciprocity is a uniquely human phenomenon. Until now, only kin and direct reciprocity has been observed in animals. In PloS Biology,  Rutte and Taborsky showed that another reciprocity mechanism could be shared by humans and other animals is present in rats: generalized reciprocity. Contrarily to other kinds of reciprocity, generalized reciprocity does not requires individual identification: in kin, direct and indirect reciprocity, you need first to identify another agent as sharing genes with you, having helped you in the past, or having helped someone else in the past. Generalized reciprocity is more anonymous: since someone help you in the past, you are more willing to help someone in the future regardless of the past and futur agent's identity. People who found a coin in a phone booth are more likely to help a stranger pick up dropped papers than control subjects who had not previously found money. Since you don't need to track and identify other's behaviors,  generalized reciprocity is less cognitively demanding, and hence probably most common in nature. In Rutte and Taborsky's experiment, a rat can pull a stick fixed to a baited tray and produces food (an oat flake) for its 'partner' (another rat); the partner is rewarded but not the 'giver'. It turns out that rats who had previously been helped were more likely (20%) to help unknown partner than rats who had not been helped. Rats followed a " “anonymous generous tit-for-tat”. 



Rutte C, Taborsky M (2007) Generalized Reciprocity in Rats. PLoS Biol 5(7): e196 doi:10.1371/journal.pbio.0050196

  • Fehr, E., & Rockenbach, B. (2004). Human altruism: economic, neural, and evolutionary perspectives. Curr Opin Neurobiol, 14(6), 784-790.
  • Fehr, E., Fischbacher, U., & Gachter, S. (2002). Strong reciprocity, human cooperation, and the enforcement of social norms. Human Nature, 13(1), 1-25.
  • Gintis, H. (2000). Strong Reciprocity and Human Sociality. Journal of Theoretical Biology, 206(2), 169-179.