Published on January 8, 2019 | Updated on January 29, 2019

CORTEX conference by Neng Gong

October 10th, 2017

Mirror Self-Recognition in Monkeys

Self-consciousnessis a hallmark of higher intelligence that can be reflected by mirror self-recognition (MSR). In contrast to human and some great apes, monkeys have consistently failed the MSR test. Here, we demonstrated that monkeys have the ability of MSR by two different training methods. First, monkeys were trained in front of a mirror to touch a light spot on their faces produced by a laser light that elicited an irritant sensation (visual-somatosensory training). After training, monkeys had learned to touch the face area in front of a mirror, and showed typical mirror-induced self-directed behaviors. However, this direct training on the monkey's face by the sensation-induced face-touching caused controversy that whether the observed MSR behaviors were just a simple conditioned response. Then we designed a new training strategy that the monkey was only trained to use the mirror as an instrument to find hidden object. We trained monkeys to touch with spatiotemporal precision a laser pointer light spot on an adjacent board that could only be seen in the mirror (visual-proprioceptive training), without any training on the monkey's face or body. After training, all monkeys spontaneously passed the standard mirror mark test, and showed typical MSR behaviors. Thus, the previous failure of demonstrating MSR in animals could be attributed to the lack of the ability in visual-proprioceptive association for the mirror images, rather than the absence of bodily self-consciousness. Our findings shed light on the origin of MSR and self-consciousness and suggest a new approach to studying its mechanism.