"Our findings suggest that the monkey brain has the basic 'hardware' (for mirror self-recognition), but they need appropriate training to acquire the 'software' to achieve self-recognition," said Neng Gong from Chinese Academy of Sciences.
In contrast to human and some great apes, monkeys have consistently failed the standard mark test for mirror self-recognition in all previous studies, the researchers noted. But once they were trained in mirror self-recognition, they continued to use mirrors spontaneously to explore parts of their bodies they normally do not see.
In the new study, monkeys were trained on a monkey chair in front of a mirror to touch a light spot on their faces produced by a laser light that elicited an irritant sensation. After two-five weeks of training, monkeys learned to touch a face area marked by a non-irritant light spot or odourless dye in front of a mirror.
Most of the trained monkeys five out of seven showed typical mirror-induced self-directed behaviours, such as touching the mark on the face or ear and then looking and/or smelling at their fingers as if they were thinking something like, "Hey, what is that there on my face?"The findings come as hopeful news for people who are unable to recognize themselves in the mirror due to brain disorders such as mental retardation, autism, schizophrenia, or Alzheimer's disease, the researchers said.
The study appeared in the journal Current Biology.