Responses to mirror image stimulation and assessment of self-recognition in mirror- and peer-reared stumptail macaques

Ten stumptail macaques (Macaca arctoides), varying in experience of conspecifics and mirrors from no experience to extensive experience throughout infancy, were tested for reactions to mirror image stimulation. Monkeys reared only with mirrors or only with one other monkey were highly responsive to their reflections, exhibiting mostly positive behaviour. Monkeys with experience of both a fully accessible cagemate and mirrors were intermediate in responsiveness, while monkeys reared with mirrors but given experience of a live conspecific behind a transparent partition responded least of all to the mirror. Monkeys reared with no experience of conspecifics at all were the most responsive. Rearing experiences influence reactions to social stimuli such as mirror image stimulation, and considerations of the novelty and complexity of the stimuli are important. Despite the most extensive exposure to mirrors yet reported, none of the monkeys showed any evidence of self-recognition.