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

Examined the influences of birth order on behavior occurring in the initial, unstructured interactions of 40 mixed-sex dyads composed of a male and a female undergraduate who each had a sibling of the opposite sex. The design contrasted 4 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. Each pair of Ss was videotaped during their 5-min initial meeting. Ss then completed questionnaires about the interaction. Results indicate that Ss 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 born women were more likely to initiate the interaction and to exceed the rate at which their male partners smiled. (64 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)