Object permanency and delayed response as spatial context in monkeys with frontal lesions.

Frontally lesioned monkeys (Macaca jasicularis) were significantly impaired relative to controls on a task (similar to that used by Piaget to test the development of object permanency) which required subjects to retrieve a grape hidden under one of three baskets. All monkeys with such lesions completely failed to reach criterion on an additional set of tasks in which the baskets were moved (i.e. the spatial context was modified) while controls performed these tasks with relative ease. Both deficits were shown to be attributable to an inability of "frontal" monkeys to process a varying spatial context.