Adrenocortical and behavioral reactions by differentially raised rhesus monkeys

Monkeys reared in social isolation or with an agemate were tested at 19 months for Cortisol responses following (1) ACTH injection and (2) initial experience in a novel playroom. Isolates had higher basal Cortisol, but did not differ from peer-raised monkeys in absolute Cortisol rise induced by ACTH or by the playroom experience. However, isolates did show more fear-disturbance-emotional behavior than did peers. The data suggest that basal Cortisol level may be a meaningful correlate of behavioral differences produced by differential rearing experiences in monkeys, but Cortisol rises induced by novel and complex stimulation are not correlated with these behavioral effects.