Impacts of early social experience on cognitive development in infant rhesus macaques

Abstract

Although much is known about the influences of early life experiences on the neurobiology and behavior of macaque models of child development, there is scant literature on cognitive development with respect to early rearing. Here, we examined the effects of rearing condition on affective reactivity and cognitive development in infant rhesus macaques. Infants were pseudo-randomly assigned to one of the two rearing conditions: nursery reared (NR, N = 32; 16 peer-reared, 16 surrogatepeer-reared) or mother-peer-reared (MPR, N = 7). During the first month of life, infants were administered the Primate Neonatal Neurobehavioral Assessment (PNNA). Beginning at 4 months old, infants were tested on cognitive tasks that assessed reward association, cognitive flexibility, and impulsivity. We found no gross cognitive differences between MPR and NR infants. However, MPR infants were more reactive than NR infants on the PNNA. Additionally, reactivity on the PNNA correlated with impulsivity, such that infants who were more reactive at 1 month of age completed fewer trials correctly on this task at 8-10 months. These findings are the first to directly compare cognitive development in MPR and NR infants, and add to the existing literature elucidating the influences of early social experience on temperament and development.

Longitudinal effects of early psychosocial deprivation on macaque executive function: Evidence from computational modelling

“…Limited research focused on early psychosocial deprivation effects on cognition in infant macaques have produced mixed findings (e.g. [ 40 , 41 ]), with research comparing deprived versus non-deprived animals especially rare. Discrepancies in findings concerning effects of early psychosocial deprivation on cognitive ability may stem from differences in age at assessment and use of different measures at different time-points, and no studies thus far have focused on EF specifically.…”

“…No previous research has used an ‘A-not-B’ task to look at macaque EF development or effects of early psychosocial deprivation, though a version such as that used with human infants could offer a valuable way to test EF without removal of the animals from their home enclosure and extensive training. A data collection approach that requires these two elements is starting to be adopted by other researchers [ 41 , 49 ], who argue that it enables a more direct comparison of cognitive development in macaques exposed to early psychosocial deprivation versus non-exposed macaques.…”