Rapid detection of snakes by Japanese monkeys (Macaca fuscata): An evolutionarily predisposed visual system.

Humans appear extremely sensitive to biologically threatening stimuli, such as snakes. In visual search tasks, humans respond to pictures of snakes faster than pictures of flowers. The authors report that macaque monkeys (Macaca fuscata), reared in a laboratory and with no experience with snakes, respond, as do humans, to pictures of snakes among flowers faster than vice versa (Experiment 1). This was also the case when grayscale pictures were used (Experiment 2). These results provide the first evidence of enhanced visual detection of evolutionarily relevant threat stimuli in nonhuman primates.