The effects of lesions of area V4 on the visual abilities of macaques: colour categorization.

Monkeys with V4 lesions and unoperated controls were tested behaviourally for their perception of the colour categories red, green, blue and yellow. As expected, the monkeys with V4 lesions took longer to acquire the colour discriminations. However, the pattern of learning was the same in the two groups of animals. Both the lesioned and the control animals made more errors when the stimuli to be discriminated belonged to the same colour category than when they belonged to different categories and thus showed normal colour categorization. The results suggest that monkeys with V4 lesions perceive the colour spectrum according to the same fundamental perceptual categories as normal monkeys and humans, and thus support the view that, in the colour domain, the four basic perceptual categories are constructed by chromatic mechanisms operating earlier than visual area V4.