A preliminary study of 6 kittens and 6 rhesus monkeys, approximately two years old, indicated that:1. The kittens as compared to older cats adapted less well to laboratory routine and learned tasks of lever-pressing and audiovisual discrimination more slowly;2. The young monkeys adapted to laboratory routine as well as the older ones but took more time to master the lever-pressing; on the other hand, they learned a series of discrimination problems as quickly as did older pre-adolescents though again somewhat more slowly than adults;3. The young animals readily developed neurotic patterns under the stress of adaptive conflict but these reactions, though resistant to 7 to 17 months of retraining, were much less generalized than those in adult controls;4. Lesions in the amygdaloid and frontal areas induced heightened sexuality and general activity level respectively, but, despite 16 to 25 months of postoperative retraining, there was no (in cats) or little (in monkeys) amelioration of neurotic patterns in the young as compared with older animals;5. Reserpine and chlorpromazine also produced only minimal and transient effects on the experimentally induced neurotic behavior.Abstract Teaser