Ontogenic development of dyadic social relationships: Assessing individual roles

Socialization processes lead to creation and differentiation of social relationships. It is often difficult to qualify them, especially due to ontogenic changes of social behavior. In this paper, an attempt is made to assess the role of each partner in a dyad by defining the quality of their overall relationship. A Social Investment Index (SII) was devised to describe these roles throughout ontogeny. SII is expressed as (G% - R%)/2, where G% and R% represent the difference between the sum of cohesive behaviors and that of disruptive behaviors divided by the overall sum of these behaviors given (G%) or received (R%) by one individual in a dyad. Results from a longitudinal study of the development of social behavior in one infant mangabey (Cercocebus albigena albigena) are used as an example. The developmental changes of the SII are presented in three dyads in a single-male group: mother-infant; "aunt"-infant; and juvenile male-infant.