Anxiety in rhesus monkey infants in relation to interactions with their mother and other social companions.

In this study the anxiety-related components of rhesus monkey infant behavior at an early stage of social development were examined. Eight rhesus infants (age 30-40 weeks) belonging to 3 captive groups were administered with an anxiogenic drug (beta-CCE; 0.2 mg/kg) and an anxiolytic drug (midazolam; 0.2 mg/kg). Saline solution was used as placebo. All infants were tested twice with each drug (four times with placebo) and their behavioral interactions with their mother and other social companions were recorded in 1-hr observation sessions. No convulsant or sedative effects of the drugs were observed. beta-CCE was associated with an increase in time spent by the infant with its mother and a concomitant reduction in proximity with other individuals and in social play. Midazolam did not affect the mother-infant interaction but increased the infant's locomotor activity away from the mother and its proximity and social play with juveniles and subadults when compared to peers. These results suggest that, although infant anxiety can be experimentally induced, it is not a major component of the mother-infant relationship. Infant anxiety, however, might affect the formation of other social bonds and play a part in the development of avoidance responses toward other individuals.