The right side of the brain helps people recognise themselves in a picture, say US researchers. A team from the Beth Israel Deaconess Medical Center in Boston report their findings in the current issue of Nature.
The study joins a growing body of evidence that demonstrates the right hemisphere plays an important role in self-awareness. Studies of self-awareness may provide unique insights into consciousness and doctors hope eventually to use such information to help people with disorders that include a lack of awareness of self and others, such as schizophrenia, autism and depersonalisation syndrome.
Keenan and colleagues worked with five patients who had each half of their brain anaesthetised briefly as part of preoperative testing for brain surgery to treat epilepsy.
Each patient was shown and asked to remember a morphed computer image blending the patient's own face with the face of a famous person.
After the anesthesia wore off, patients were asked to choose which face they remembered seeing, their face or the famous face, although they saw only the morphed image when they were under anaesthesia.
While the left hemispheres of the five patients were anaesthetised, their right brains could apparently recognise themselves in the morphed images. But after numbing of right hemisphere four out of five patients only remembered seeing the famous person.
In a follow-up experiment, 10 people in the neurology department were shown a morphed image of their face with the face of a famous person and a second image of a familiar colleague's face with a famous face. Researchers found significantly greater right brain activity when people viewed a self-morph compared to a co-worker-morph.
"One of the astonishing findings in psychology is that humans and the apes (including chimpanzees, orangutans, and some gorillas) are the only species that recognise their own faces in a mirror," says Keenan, who began researching self-awareness as a graduate student. "It has been thought that this ability is a hallmark of consciousness. To know that our own face is ours inevitably requires a knowledge of the self. Without self-knowledge, it would be seemingly impossible to recognise who we are."
Puce, who studies face recognition, says that the people in Keenan's experiments would have been using their right brain to recognise the familiar faces of colleagues and famous people - regardless of whether they remembered their name.They used the language skills and verbal memory of the left brain to remember the names of the famous people.