one another, maintaining relatively large individual distances. Like their bonnet counterparts, pigtail dyads are initially mutually focused on one another, maintaining long periods of contact and nursing. But unlike the bonnets, pigtail mothers do not allow others to contact their young infants, and as the infants attempt their initial excursions from them, the pigtail mothers actively restrain and protect them closely. Within a few months, however, the pigtail mothers, as they move towards returning estrus, begin active and vigorous rejection, removal, and weaning of their four-to-eight-month-olds. ( Rosenblum, 1971 a).
Of relevance to the diverse and often delayed effects of these differences in the pattern of the early attachment relationship are two salient outcomes of these normative species differences. Despite the fact or perhaps because of the fact that pigtail mothers actively reject their infants repeatedly over a period of months, pigtail infants, in marked contrast to similar aged bonnets, show dramatic negative responses, including mild depression following the birth of a sibling, and frequently show marked and often sustained depression in response to maternal separation ( Rosenblum & Kaufman, 1968). Moreover, when observed over long periods of the life cycle, pigtails show continued high levels of attachment to their mothers and their siblings, whereas bonnets show little selectivity for contact or interaction with members of their consanguinal family units, including the mother ( Rosenblum, 1971b). Thus, rejection by the mother, in spite of the increases in time apart that may initially ensue, nonetheless appears to result in increased rather than diminished dependence on and attachment to the maternal and other associated figures.
What then are the possible mechanisms through which these diverse patterns of early interaction impact upon the infant's developing changes in the intensity and exclusivity of attachment to the mother? I suggest that this body of data may be understood, at least in part, in terms of the way in which the infant's movements into the nondyadic world are orchestrated. In keeping with classic concepts of arousal and learning (cf. "The Yerkes-Dodson Law"), when infants are forced or otherwise coerced into breaking contact with the mother, their capacity to learn the distinguishing features of their environment and the responses appropriate to them is diminished as a consequence of the relatively high level of fear or anxiety that these young animals experience during these forced periods of noncontact.