Heterosexual couples and homosexual rivals: Sex differences in romantic jealousy when the rival is the same sex as your partner

Research testing hypotheses derived from evolutionary psychology about sex differences in romantic jealousy has been hampered by a confirmationist hypothesis testing strategy. We report three studies conducted in Austria and Australia that employ a conditional hypothesis testing strategy to investigate variations in sex differences in jealousy under different relationship conditions, namely opposite-sex and same-sex infidelity among heterosexual individuals. In Study 1, heterosexual women found a same-sex sexual infidelity more aversive than heterosexual men did, and this difference persisted after adjusting for other likely predictors of this difference. In Studies 2 and 3, enhanced sexual jealousy in heterosexual men was not observed when the rival was the same sex as his partner. This effect was reversed for women, who were more distressed by sexual versus emotional infidelity when the rival was the same sex as her partner. An explanation for this set of findings, based on sex differences in sexual and attachment motivation, is proposed.