NEUROBEHAVIORAL ASSESSMENT IN RHESUS-MONKEY NEONATES (MACACA-MULATTA) - DEVELOPMENTAL-CHANGES, BEHAVIORAL STABILITY, AND EARLY EXPERIENCE

This prospective study documented developmental changes, individual stability, and the effects of early experience on the neurobehavioral repertoire of nursery-reared rhesus monkey neonates (Macaca mulatta) tested repeatedly across the first month of life. Thirty-six infants were tested three times weekly on a substantially modified version of the Neonatal Behavioral Assessment Scale. The infants were reared under several conditions in which their exposure to animate and inanimate objects varied. Eleven infants were reared with only a cloth, 8 were reared with an upright cloth-covered surrogate, 7 were reared with an upright movable cloth-covered surrogate, and 10 were reared with an upright movable cloth-covered surrogate and regular exposure to peers and novel toys. Infants reared with a movable surrogate demonstrated superior motor maturation in comparison to those reared with only a cloth or cloth-covered surrogate. However, infants reared with a movable surrogate as well as exposure to peers and novel toys showed not only greater motor maturation than cloth-reared infants but also greater responsiveness on orientation items and lower ratings of fearfulness when compared to infants in the three other conditions. Furthermore, the data indicate that behavioral stability of individual differences can be demonstrated in individuals undergoing rapid developmental change regardless of rearing conditions.