title: Number of older brothers and sexual orientation: new tests and the attraction/behavior distinction in two national probability samples.
abstract: The extent to which number of older brothers or "fraternal birth order" predicted the 2 main components that researchers have traditionally used to conceptualize sexual orientation-that is, psychological attraction and sexual behavior-was examined in 2 recent national probability samples. In both studies, fraternal birth order predicted same-sex attraction in men, with each additional older brother increasing the odds of homosexual attraction by an average of 38%. Results also indicated that the fraternal birth order/same-sex attraction relationship in men was independent of sexual behavior, including early same-sex behavior. No sibling characteristics predicted sexual orientation in women. Results suggest experience-based theories (e.g., early same-sex play) of the fraternal birth order effect in men are unlikely to be correct.
authors.affiliation: Department of Community Health Sciences, Brock University, St. Catharines, Ontario, Canada. tbogaert@spartan.ac.brocku.ca
authors.forename: Anthony F
authors.initials: AF
authors.lastname: Bogaert
mesh_terms: D000293:Adolescent; D000328:Adult; D001722:Birth Order; D005260:Female; D006716:Homosexuality / Q000523:psychology*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012725:Sexual Behavior; D035781:Siblings / Q000523:psychology*; D018709:Statistics, Nonparametric; D006113:United Kingdom; D014481:United States