Plasma cortisol is associated with handedness in infant rhesus monkeys

In this research we examined the relationship between plasma cortisol and h andedness in infant rhesus macaques (Macaca mulatta). Specifically, we test ed the hypothesis that stress functioning is related to hemispheric special ization and manifested in a positive correlation between cortisol levels an d the frequency of right- versus left- hand use. we found a significant pos itive relationship between cortisol levels sampled at ages 1 and 3 months a nd lateral bias toward greater use of the right hand versus left hand sampl ed between ages 4 and 11 months. Further; we found a significant negative r elationship between cortisol sampled at age 5 months and strength of latera l bias (independent of direction). These data suggest an early developmenta l ii influence of stress functioning on hemispheric specialization for manu al control in infant monkey's. (C) 2001 John Wiley & Sons, Inc.