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.