Current Biology, Volume 19 Supplemental Data Face Processing in the Chimpanzee Brain

Face expertise in chimpanzees Previous studies in our lab have demonstrated that chimpanzees, as opposed to monkeys, are highly skilled at discriminating unfamiliar conspecifics ’ faces. These studies have been conducted using computerized testing systems that present faces in a matching-to-sample (MTS) format (Figure S1). When first learning to discriminate unfamiliar conspecifics ’ faces in our lab, chimpanzees performed above chance on day one of testing. In contrast, rhesus monkeys with the same level of computerized training required over 100 presentations before their performance exceeded chance levels (Parr et al., 2000). A more complex version of the MTS task was then used to examine the recognition of specific individuals from faces. In these tasks, two different photographs of the same individual were presented as the matching pair, and a third picture of a different individual was used as the nonmatch. Thus, matching requires recognizing the facial configurations of the individuals and not specific features of the photographs. In these individual recognition (IR) tasks, chimpanzees also performed above chance within a single testing session after having seen each trial twice, whereas monkeys required an additional 60 trials before they performed above chance (Parr et al., 2000). This species difference was confirmed more recentl