Behavioral and physiological responses of mother and infant squirrel monkeys to fearful stimuli

The behavioral and adrenocortical responses of feral squirrel monkey mothers and their laboratory-born infants were measured following exposure to a live snake and to a flying predator model (hawk). The dyads were either socially or individually housed. The different stimuli were presented above the home cage for 1 hr; behaviors were observed during this period. Blood samples were obtained at the end of the test session and assayed for cortisol. The results indicated that individually housed dyads markedly increased their time spent in contact and their avoidance of the stimuli, and showed increased levels of cortisol when exposed to the snake or hawk model. Socially reared monkeys responded only to the snake. Thus, the presence of social partners ameliorated the response to the hawk model. The marked increase in contact during the presentation of the fear-eliciting stimuli may be partly responsible for the infants' response.