The effects of varying environmental demands on maternal and infant behavior.

3 groups of macaque mother-infant dyads were observed while each lived in ecological settings that differed in their level of foraging demand and, hence, the amount of work each mother was required to perform to obtain her daily rations. 2 groups (LFD and HFD) lived in stable low- and high-demand environments, respectively. The third group (VFD) lived in a variable-demand environment in which 2-week periods of HFD and LFD conditions were alternated, without external cues. Observations suggested that VFD subjects were unable to predict or rapidly adapt to the biweekly changes in food availability. Whereas LFD adults scored lowest in dominance-related behaviors and highest in affiliative behavior (social grooming), VFD adults showed the highest levels of dominance patterns and the lowest levels of grooming. VFD infants showed the most sustained clinging to mother, the lowest levels of social play and exploration, the highest levels of affective disturbance, and repeated evidence of depression as the study progressed. These findings suggest that in monkeys, as in humans, when, because of competing demands, mothers are psychologically unavailable to their infants, attachments are less secure, normal development is disrupted, and psychopathological patterns are more likely to emerge.