Reactions of capuchin monkeys (Cebus apella) to multiple mirrors.

This study attempted a new manipulation to prompt mirror self-recognition in a monkey species through simultaneous exposure to two mirrors. Four capuchin monkeys (Cebus apella) were exposed to one large and one small mirror object with different reflective or configurational properties, which was thought to deepen their understanding of mirrors. The monkeys predominantly engaged in looking behaviours towards the large mirror, which decreased over sessions. There was also an increase in looking behaviours towards the small mirror object when it reflected an undistorted image compared to the control condition. No instances of self-directed responses, oblique looks or manipulations of both mirror objects in combination were observed. The results confirm and expand on previous reports of failure to find evidence of mirror self-recognition in monkeys.