Snakes trigger alarm in our brains, study shows
Ever wonder why snakes inspire such fear? A new study on monkeys suggests that the brain has specific cells that fire off rapid warnings when confronted with slithery danger.
Certain neurons respond "selectively" to images of snakes, and they outpace comparable neurons that react to visuals of faces, hands or geometric shapes, the researchers say.
The report published on Monday in the Proceedings of the National Academy of Sciences offers new evidence to support the notion that primates evolved keen vision skills so they could survive the threats that snakes pose in the jungle.
"It really strengthens the argument that snakes are very important for the evolution of primates," said lead co-author Lynne Isbell, a professor in the anthropology department at the University of California Davis.
"Snakes elicited the strongest, fastest responses," said the study, co-authored by Quan Van Le of the University of Toyama in Japan and researchers at the University of Brasilia in Brazil. The research was done using two young macaque monkeys born in captivity in Japan. Researchers said they believed the monkeys had no chance to encounter snakes prior to the experiment.
Scientists surgically implanted microelectrodes in a part of the brain known as the pulvinar, which is involved in visual attention. Then they showed the monkeys various colour images on a computer screen, including snakes in various positions, threatening monkey faces, pictures of monkey hands and simple shapes like stars or squares.
Seeing a snake caused the brain to fire off rapid fear responses that were unparalleled.
Researchers found that of about 100 neurons that fired off when presented with at least one of the image types, 40 per cent had the largest response to snakes. That was the biggest group.