Form perception in stumptail macaques following posterior parietal and lateral frontal lesions.

Monkeys with bilateral posterior parietal and lateral frontal ablations were compared with normal animals on a series of four tests for their ability to relate elements of a visual pattern on the basis of the Gestalt principle of proximity. The operated animals showed no clear impairment on these tests of perceptual grouping. The three groups of monkeys were then trained to discriminate two faces and tested for generalisation to different views of the same faces. The pariental-operated monkeys showed less generalisation than the other animals to lateral mirror-images of the training stimuli, but more generalisation to inverted mirror-images. It is concluded that any deficit in "gestalt" perception following such lesions must be at a relatively high level.