Effects of early parenting on growth and development in a small primate

We report here a study of the impact of caregiver-infant relationships on physical growth and behavioral development in a small primate, the common marmoset. Somatic growth was assessed from measurements of body weight, knee-heel length, head-tail length, head circumference, and pudendal pad width in females or testis volume in males obtained from unanesthetized monkeys. Behavioral information was gathered by focal animal samples for discrete rearing behaviors. Our data suggest that the frequency of positive parental behaviors during infancy is correlated with stature when the monkeys reach 10 and 20 wk of age. Furthermore, we found that juveniles that were mistreated by their parents during infancy were smaller in body weight, knee-heel length, and head-tail length, and they demonstrated abnormal social behavior. Finally, to address whether the apparent decreased growth observed in the young animals that had experienced negative parenting was also associated with alterations in hypothalamic-pituitary-adrenal (HPA) axis function, we examined the plasma ACTH and cortisol responses to synthetic ovine corticotropin-releasing hormone (oCRH) in these animals. We found that the incremental cortisol response to exogenous oCRH was significantly lower in the young adults that had experienced negative parenting during infancy compared with those who had nonabusive parents, indicating altered hypothalamic-pituitary-adrenal axis function in these animals. Our findings suggest that the quality of parental care influences later growth and behavior in the young marmoset.