Your Biological Disposition to Spotting Snakes

Ever spotted a snake in the undergrowth and wondered how the little jerk’s camouflage failed him? There may be a biological reason for this: you have cells in your brain that respond specifically to snakes.

A study published in PNAS found that an extra cluster of neurons in the pulvinar, a region of the brain that receives signals from the eyes, is responsible for identifying snakes. Lots of mammals have pulvinars, but only primates have the extra cluster. Researchers attached electrodes to the pulvinars of macaques—which could interpret the activity of ninety-one different neurons—and trained them to press a button when they were presented with a picture. Pictures of other monkeys, foliage, and geometric shapes didn’t faze the macaques too much, but pictures of snakes prompted a strong response from all ninety-one neurons. This is particularly striking, as the macaques had never seen a snake before.

This supports previous research, which has seen both rural and urban children equally quick at spotting snakes and monkeys who had never seen snakes identifying them as objects they fear. Researchers theorize that primates evolved this very specific ability as a way of defending ourselves against a dangerous and regularly encountered adversary. We think that researchers should next look into why this ability seems to abandon us every time we visit the zoo, or, alternatively, whether there are actually snakes in that damn reptile house, because we just see logs, leaves, and rocks.

This is a test