The influences affecting sibling interaction among adults were investigated. Twenty-one predictor variables, subsequently reduced to nine, were examined through multiple regression analysis for their contribution to the explained variance in three dependent measures: frequency of contact with an adult sibling, obligation to have contact with the sibling, and desire for contact with the sibling. The predictor variables represented four conceptual areas of influence on sibling interaction: qualities of the sibling relationship; structure of the sibling constellation; structure of the siblings' families of procreation; and demographic characteristics of the siblings. Geographic proximity was also examined.

The investigation utilized adult respondents over 25 years of age, with living siblings. The sample was drawn from the Roanoke, Virginia, urbanized area using a two-stage systematic design involving telephone and mail surveys. A completed sample of 313 adults was obtained, yielding a net response rate of 82%. The respondent in each household and the respondent's sibling were chosen at random.

The reduced predictor equation explained 69% of the variance in frequency of contact, 37% of the variance in obligation to have contact, and 65% of the variance in desire for contact. The combination of the predictors was statistically and substantively significant for each of the criterion measures.

The results suggest that proximity, emotional closeness, obligation, and sex are the most important influences on adult sibling interaction in general. The relative contribution of these predictors, however, varies for the different aspects of interaction represented by the criterion measures. Proximity is more explanatory of actual behavior, but relationship qualities are more important in explaining the motivation for contact.