Data are presented to both support and extend research findings concerning the effects of early experience on nonhuman primate learning ability. Enriched monkeys tested in their home living environment performed more proficiently than monkeys separated from their living environments and tested in an adjoining room. Further, monkeys reared in enriched environments were superior to partially isolated controls on the complex oddity tasks but not on 2-choice discrimination or delayed-response problems.

Abstract. Delayed response ability, and to a lesser extent visual discrimination performance, is seriously impaired by extensive bilateral damage to the frontal lobes. Reciprocal anatomical connections between the frontal and temporal lobes suggested that massive lesions in both lobes might produce an impairment more complete than that resulting from frontal lobectomy alone. Five monkeys were given combined bilateral frontal and anterior-temporal lesions, and were found to be inferior to both frontal lobectomized monkeys and to unoperated controls on the object discrimination task. The combined lesion did not increase the deficit on delayed response over that obtained after only bilateral frontal lobectomy. Results indicate that the anterior-temporal neocortex is involved in the mediation of visual discrimination ability.

Bilateral ablation of dorsolateral frontal cortex in the newborn animal failed to produce the frontal lobe syndrome typical of the adolescent and adult stages. The crucial tests (delayed response, string tests, and discrimination learning) were performed 3 to 4 months postoperatively. At this time, no significant differences between normal animals and animals with prefrontal lesions were found.

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