An ‘indirect reputation’ experiment in four great ape species

Reputation is defined as knowledge of a person’s typical behaviour based on that person’s past behaviour. Indirect reputation refers to knowledge gained from observing events between third parties. This experiment was devised as a methodology for learning about indirect reputation in non-human apes (inspired by a recent body of human experiments). Four great ape species (Pan troglodytes verus, Pan paniscus, Gorilla gorilla gorilla, Pongo pygmaeus abelii) were tested on a simple paradigm where every subject passively observed two types of food sharing incident that occurred between human actors. One (1) was a nice person incident (a "nice" person gave some of her grapes to a human who begged for them). The other (2) was a nasty person incident (a "nasty" person refused to allow the beggar to take any grapes). After observing both incidents, the subject was allowed into a compartment where both nice and nasty persons were sitting side-by-side at plexiglas windows (with open food holes). Both humans were holding a container of grapes but neither fed the subject. This was a test of which human (nice/nasty) the subject prefers to approach. One measure of preference was the percentage of seconds that the subject spent at either window. Only chimpanzees (n = 17) spent significantly more seconds at the nice person’s window than the nasty person’s. The results were not significant for bonobos (n = 5), orangutans (n = 5), or gorillas (n = 5). One interpretation of these data is that chimpanzees were using the passively observed incident to guide their subsequent food seeking behaviour