The effect of occipital lesions on visually guided behavior in the monkey. I. Influence of the lesions on final capacities in a variety of problem situations.

Abstract

7 macaques were studied, all of them but one having occipital lobectomies in 1 hemisphere, and 5 of them having all or a large part of the macular cortex of the opposite hemisphere removed. Tests were made after both stages of operation. Tests were made on the following: (1) liminal discrimination of monochromatic colors, (2) liminal discrimination of light intensity, (3) discrimination of geometric figures, (4) choice capacity, (5) immediate memory, (6) insight, (7) searching ability, (8) reaction on patterned string tests. Operated animals showed final performance within the range of normal animals. When retention was involved (pattern tests) there was temporary loss of function which could not be accounted for in terms of operative shock, simple forgetting, or loss of learned associations. Persistence of preoperative orientation responses and the existence of a gap in the visual field were postulated to account for the errors in retention. Closing of the gap in the visual world was thought to take place through learning to use perceived objects as inferring the existence of a larger situation and by gradual development of a capacity to respond on the basis of less than normal cues.