Many people are afraid of snakes – indeed, humans and primates can detect snakes faster than innocuous objects. Quan Van Le of the University of Toyama and colleagues have found neurons in the primate medial and dorsolateral pulvinar that respond selectively to images of snakes. Compared to three other categories of stimuli – monkey faces, monkey hands and geometrical shapes – snakes gave the fastest and strongest responses, which were not reduced by low spatial filtering.

The response to snakes seems to be hardwired and the parts of the brain involved are unique to primates, among mammals. This gives hard neuroscientific evidence for the "snake detection theory", which suggests that primate vision evolved in part driven by the need to recognize snakes.