Attachment relationships in infant twins: the effect of co-twin presence during separation from mother.

In this study the roles of the mother and the co-twin in inhibiting emotional arousal and reducing manifest distress of a twin who had been isolated in a modified strange situation were compared. The subjects were 15 children, each a member of a twin pair. The subjects were placed in a playroom under three conditions in the following order: (a) mother and twins present; (b) twins together, mother absent; (c) subject isolated from both co-twin and mother. The episodes in which all partners were together were alternated with brief separations. The subjects' distress was minimal when they were separated from the mother with the co-twin present. Upon reunion, stable social behavior was quickly restored. However, separation from the mother and co-twin produced a high level of distress for the subjects. When reunited, the isolated twin initiated physical contact with the mother, soliciting and receiving comfort from her. Furthermore, the distress of the isolated twin was transmitted to the co-twin who had remained with the mother during the isolation period. The nonisolated twin also solicited comfort from the mother. The presence of the co-twin during the reunion following isolation had little effect in reducing the subject twin's distress.

Neonatal sex and birth-order effects on behaviors of mothers and temporary caretakers during bottle-feeding.

This study examined the effects of neonatal sex and birth order on maternal caretaking patterns for pre-attachment behaviors shown by mothers and instrumental behaviors seen in both mothers and temporary caretakers. Observational category scores were obtained for mothers of 20 newborn infants and for temporary caretakers observed in a 15 min bottle-feeding situation. A repeated measures analysis of variance design was used to partition categories into caretaking classifications and to evaluate the effects of infant sex and birth order. Significant main effects for caretaker (p less than .05) were obtained: six mother-high, pre-attachment categories, and seven mother-low, instrumental behavior categories. Maternal scores sensitive to infant sex and birth order were identified from Caretaker x Sex x Birth Order interactions (p less than .05). Birth order differences affected maternal behaviors directed toward sons more substantially than those directed toward daughters. Mothers held first-born sons upright in tactual contact with the trunk, whereas daughters were held supine on the lap and exposed to frequent maternal smiling.

Early social deprivation and the ontogeny of unrestricted social behavior in the laboratory rat.

The unrestricted adult social and nonsocial behavior of albino rats isolated from 21 to 70 days of age was compared with the behavior of rats receiving normal social experience. Isolated animals exhibited aberrant self-manipulative behaviors during the period of isolation, and both isolate-reared males and females were more aggressive than their group-reared counterparts. The hypothesis that females are buffered against the effects of social isolation received little support. Numerous gender differences and differences in the gender of the object of social response were found for both isolate- and group-reared rats. Gender and Rearing Conditions were relatively independent influences on behavior with few Gender x Treatment interactions reaching significance.