Psychology, Department of


Date of this Version



Stevens, J.R. & King, A.J. (2012). The lives of others: Social rationality in animals. In R. Hertwig, U. Hoffrage, & the ABC Research Group (Eds.), Simple heuristics in a social world (pp. 409-431).


Copyright 2012 Oxford: Oxford University Press.


Amanda sits waiting in a nail salon. She is on a day out with her two neighbors Bridget and Camille, who are already being serviced by different attendants. After observing Bridget’s body jolt several times, Amanda makes her way over to Camille’s attendant for her own service. By using a simple social cue, Amanda has likely saved herself a good bit of pain and may even have established a life-long relationship with the apparently more skilled attendant.

If you replace “nail salon” with “cleaning station”, these circumstances apply perfectly well to an instance of social rationality in fish! Cleaner fish (e.g., the cleaner wrasse, Labroides dimidiatus) establish cleaning stations to feed on parasites attached to the skin of various species of client fish. Sometimes, though, instead of taking the parasites, the cleaner fish bite a piece of skin or mucus—both of which are preferred to parasites. When this happens, the client fish jolt. These jolts, paired with the client fish chasing the nippy cleaners, provide social cues about the cooperativeness of the cleaners, and client fish use this information when deciding which cleaner to visit (Bshary, 2002). Attending to the behavior, choices, and decision outcomes of others can be beneficial, and this socially savvy behavior is by no means restricted to nail salons and cleaning stations, or even to any particular species or class of animals. Instead, we shall argue that social rationality is a key aspect of the lives of animals.