A "bent twig" model which incorporates Annett's genetic handedness theory with an environmental component predicted characteristics of college women likely to excel on a mental rotation task. Those likely to have the necessary combination of genetic potential and prior experiences are right-handed women with non-right-handed relatives who rate themselves high in spatial experiences. This subgroup significantly outperformed all other groups of right-handed women on the Vandenberg Mental Rotation Test. This study provides support for the view that family handedness and spatial experiences are important factors influencing mental rotation ability in women.