On the social advantages of having an older, opposite-sex sibling: Birth order influences in mixed-sex dyads.

Abstract

This study examined the influences of birth order on behavior occurring in the initial, unstructured interactions of 40 mixed-sex dyads composed of a man and a woman who each had a sibling of the opposite sex. The design contrasted four different dyad types: (a) a firstborn man paired with a firstborn woman, (b) a firstborn man paired with a last born woman, (c) a last born man paired with a firstborn woman and (d) a last born man paired with a last born woman. Results indicated that individuals with an older, opposite-sex sibling were particularly likely to have rewarding interactions with strangers of the opposite sex. Relative to firstborn men, last born men talked nearly twice as long, asked more questions, and evoked more gazes, verbal reinforcers, and self-reported liking from their female partners. Relative to firstborn women, last bora women were more likely to initiate the interaction and to exceed the rate at which their male partners smiled. These findings are inconsistent with Toman's (1961, 1976) family constellation theory but are consistent with the results of various empirical studies that have also documented the greater social skills of later borns.