Monkeys recognize the faces of group mates in photographs

Abstract

Nonhuman primates posses a highly developed capacity for face recognition, which resembles the human capacity both cognitively and neurologically. Face recognition is typically tested by having subjects compare facial images, whereas there has been virtually no attention to how they connect these images to reality. Can nonhuman primates recognize familiar individuals in photographs? Such facial identification was examined in brown or tufted capuchin monkeys (Cebus apella), a New World primate, by letting subjects categorize facial images of conspecifics as either belonging to the in-group or out-group. After training on an oddity task with four images on a touch screen, subjects correctly identified one in-group member as odd among three out-group members, and vice versa. They generalized this knowledge to both new images of the same individuals and images of juveniles never presented before, thus suggesting facial identification based on real-life experience with the depicted individuals. This ability was unexplained by potential color cues because the same results were obtained with grayscale images. These tests demonstrate that capuchin monkeys, like humans, recognize whom they see in a picture.face recognition ͉ individual discrimination ͉ oddity ͉ primate ͉ visual discrimination

Capuchin monkeys (Cebus apella) treat small and large numbers of items similarly during a relative quantity judgment task

“…All monkeys previously had been trained to use a joystick with their hands to control a cursor on a computer screen within the previous 6 months (see Evans et al, 2008 for training details), but this was their only prior experimental history with the joystick apparatus. However, one monkey (Mason) was trained on a touchscreen computer and had participated in several facial-recognition studies that involved discriminating conspecific faces (Pokorny & de Waal, 2009a, 2009b; Pokorny, Webb, & de Waal, 2011). The monkeys are socially housed and separate voluntarily for computer testing.…”

Monkeys benefit from reciprocity without the cognitive burden

“…It is important to note, however, that the same situation occurs between groups of wild capuchins, which also have frequent auditory and occasional visual contact with neighboring groups (30). Previous research with the same capuchins tested in the present study has demonstrated successful discrimination between in-group and out-group members' facial images without any additional cues by using a touchscreen face-recognition task (39).…”

Self-control assessments of capuchin monkeys with the rotating tray task and the accumulation task

“…They had participated in only a few cognitive studies in our laboratory that involved different quantity judgments (Beran and Parrish, in press; Parrish, Agrillo, Perdue, and Beran, 2016; Parrish, Brosnan, and Beran, 2015a). One monkey (Mason) was trained on a touchscreen computer and had participated in several facial-recognition studies that involved discriminating conspecific faces (Pokorny & de Waal, 2009a, 2009b; Pokorny, Webb, & de Waal, 2011). This was the first effort to assess their self-control using the RT and they had only very limited experience with the AC tasks used in Experiments 1 to 3.…”