Rapid categorization of natural images by rhesus monkeys.

Two rhesus macaques were tested on a categorization task in which they had to classify previously unseen photographs flashed for only 80 ms. One monkey was trained to respond to the presence of an animal, the second to the presence of food. Although the monkeys were not quite as accurate as humans tested on the same material, they nevertheless performed this very challenging visual task remarkably well. Furthermore, their reaction times were considerably shorter than even the fastest human subject. Such data, combined with the detailed knowledge of the monkey's visual system, provide a severe challenge to current theories of visual processing. They also argue that this form of rapid visual categorization is fundamentally similar in both monkeys and humans.