Rhesus monkeys don't realize that when they look in a mirror, they are seeing their own face, but a new study has demonstrated that the monkeys can learn to recognize themselves in mirrors.
Neng Gong of the Chinese Academy of Sciences, said that their 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.
In earlier studies, scientists had offered monkeys mirrors of different sizes and shapes for years, even beginning at a young age. While the monkeys could learn to use the mirrors as tools for observing other objects, they never showed any signs of self-recognition. When researchers marked the monkeys' faces and presented them with mirrors, they didn't touch or examine the spot or show any other self-directed behaviors in front of those mirrors in the way that even a very young person would do.
In the new study, Gong and his colleagues tried something else. They sat the monkeys in front of a mirror and shined a mildly irritating laser light on the monkeys' faces. After 2 to 5 weeks of the training, those monkeys had learned to touch face areas marked by a spot they couldn't feel in front of a mirror. They also noticed virtual face marks in mirroring video images on a screen. They had learned to pass the standard mark test for mirror self-recognition.
The researchers said that the findings in monkeys 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 study is published in the Cell Press journal Current Biology.