Rhesus Monkeys (Macaca mulatta) Do Recognize Themselves in the Mirror: Implications for the Evolution of Self-Recognition

Abstract

Self-recognition in front of a mirror is used as an indicator of self-awareness. Along with humans, some chimpanzees and orangutans have been shown to be self-aware using the mark test. Monkeys are conspicuously absent from this list because they fail the mark test and show persistent signs of social responses to mirrors despite prolonged exposure, which has been interpreted as evidence of a cognitive divide between hominoids and other species. In stark contrast with those reports, the rhesus monkeys in this study, who had been prepared for electrophysiological recordings with a head implant, showed consistent self-directed behaviors in front of the mirror and showed social responses that subsided quickly during the first experimental session. The self-directed behaviors, which were performed in front of the mirror and did not take place in its absence, included extensive observation of the implant and genital areas that cannot be observed directly without a mirror. We hypothesize that the head implant, a most salient mark, prompted the monkeys to overcome gaze aversion inhibition or lack of interest in order to look and examine themselves in front of the mirror. The results of this study demonstrate that rhesus monkeys do recognize themselves in the mirror and, therefore, have some form of self-awareness. Accordingly, instead of a cognitive divide, they support the notion of an evolutionary continuity of mental functions.

Self-monitoring of social facial expressions in the primate amygdala and cingulate cortex

“…Notice that macaques have been repeatedly reported to fail the mirror self-recognition test (23,24) (but see ref. 25), yet strongly respond to self views (26), in line with the increased facial expressions we observed in the mirror condition ( Fig. S3B; P < 0.01, ANOVA) and comparable to the peer condition.…”

Do rhesus monkeys recognize themselves in mirrors?

“…Given the potentially profound importance of extending the capacity for mirror self-recognition to macaques, and the fact that the claim runs contrary to the overwhelming negative evidence in monkeys, this article needs to be examined with utmost care and scrutiny. Here, we identify numerous flaws with Rajala et al [2010], and conclude that their claim of self-recognition in rhesus monkeys is not supported by the evidence.…”

“…A recent article, however, claims to have demonstrated mirror self-recognition in rhesus monkeys [Rajala et al, 2010]. Individually housed monkeys had been fitted with acrylic blocks permanently attached to their skull for unrelated neurophysiological studies.…”

“…The problems in Rajala et al [2010] start with coverage of the self-recognition literature, which is both selective and inadequate. Among other things, it is stated that ''some'' elephants and dolphins have passed the mark test.…”

Evolution of consciousness: Phylogeny, ontogeny, and emergence from general anesthesia

“…The distinction between great apes and monkeys would seem to provide a clear demarcation in the capacity for consciousness between species. Numerous studies have supported this demarcation, with multiple failed attempts to detect self-awareness in monkeys, despite one recent report to the contrary (91). However, a number of methodological concerns limit enthusiasm for the one contrary study, and overall the data continue to suggest that macaques do not evidence MSR behavior (92).…”