Attachment in monkey infants raised in variable- and low-demand environments.

12 bonnet macaque (Macaca radiata) mother-infant dyads were studied. For 14 weeks, beginning when the infants were a mean age of 11.2 weeks, the dyads were housed and observed under different foraging-demand conditions for the mothers: 6 dyads in a low-foraging-demand (LFD) condition and 6 dyads in a variable-foraging-demand (VFD) conditions. For VFD mothers, demand varied between low and high in 2-week blocks. Differences between the LFD and VFD groups were minimal during this period; there was, however, more maternal grooming and shorter separation bouts in the VFD group than in the LFD group. The dyads were then challenged by brief introductions to a novel environment. The challenge revealed that frequency of breaking dyadic contact and levels of play were significantly lower for the VFD infants than for the LFD infants, perhaps as a consequence of less secure attachment.