Recognition of monkey faces by monkey experts

Human beings automatically discriminate human faces at the individual level. Infants aged 3 months implicitly recognise monkey faces, but this capacity disappears as recognition skills mature. Expertise is known to affect recognition capacities for different categories of stimuli that are not even face-like in their configuration. We have explored the capacity of adult experts and non-experts in primatology to recognise monkey faces in both explicit and implicit recognition tasks. In the explicit task, where subjects received the instruction to recognise a face seen previously, experts proved to be more accurate than non-experts. Experts were more affected by inversion than non-experts, suggesting that the processing of those faces is based on their configuration, as is generally observed for human faces. This replicates findings from Diamond and Carey (J Exp Psychol Gen 115:107-117, 1986) in dog experts. In the implicit recognition task, assessed by a visual paired comparison task where no instruction of recognition was given, automatic discrimination was observed for human faces but not for monkey faces. These results suggest that experience acquired by the time of adulthood did not lead the experts to develop recognition skills to the point of matching those exhibited for human faces.