Humans and great apes such as bonobos, gorillas and chimpanzees have the ability to recognize themselves in the mirror, a behavior otherwise known as self-recognition, but rhesus monkeys only see their reflection as another monkey or even a rival.
A group of Chinese researchers, however, has found that over time and with training, the rhesus monkey, a native to Central, South and Southeast Asia, can also learn to recognize their own image.
The macaques even get to enjoy looking at themselves in the mirror curiously examining their image just like humans once they have learned self-recognition, a sign of empathy in humans.
For their study published in the journal Current Biology on Jan. 8, neuroscientist Neng Gong, from the Chinese Academy of Sciences in Beijing, China, and colleagues, placed a group of seven monkeys in front of a mirror and then projected a red light dot on various locations of their face using a powerful laser light that caused mild irritation.
The animals were given food as a reward when they touch the illuminated area and after two to five weeks of training, the monkeys learned to touch the areas on their face that were marked by the laser dot or dye mark on the mirror.
Gong and colleagues also noticed that when they showed the animals the video mirror images of their face, the animals touched the virtual mark on it.
Most of the monkeys in the study likewise exhibited self-directed behaviors such as touching the mark on their face and then looking at or even smelling their fingers, which led to the researchers concluding that the monkeys have passed what is known as the mark test for mirror self-recognition.
"We show that rhesus monkeys could acquire mirror-induced self-directed behaviors resembling mirror self-recognition following training with visual-somatosensory association," the researchers wrote. "Four control monkeys of a similar age that went through mirror habituation but had no training of visual-somatosensory association did not pass any mark tests and did not exhibit mirror-induced self-directed behaviors."
Gong said that their study suggests that the brain of the monkey has the basic hardware for self-recognition but it just needs the right training in order to acquire the software to achieve this.
State University of New York evolutionary psychologist Gordon Gallup Jr., who developed the mark test for measuring self-recognition in animals, however, is skeptical pointing out that the study only showed that the monkeys could be trained to do something but this does not mean that the animals had a grasp of what they were doing.
