A SEX DIFFERENCE IN TURNING BIAS IN HUMANS

A large body of literature has documented the existence of individual preferences in turning direction among rodents which appear to be depe ndent on striatal dopaminergic mechanisms. Recent work has indicated t hat humans also demonstrate individual turning preferences, and that t hese preferences may also be related to the nigrostriatal dopamine sys tem. We describe here a new method for measuring turning preferences i n humans and report a sex difference in the magnitude of the direction al preference. While both males and females tended to turn towards the right, this tendency was significantly stronger among females. Analys es of test-retest reliability across two sessions (1-2 weeks apart) in dicated that, in general, the rotation task elicited consistent turnin g biases. However, the turning biases of males and of females using or al contraceptives were significantly more consistent than those of reg ularly cycling females. These results are compatible with the animal l iterature and provide indirect evidence that ovarian hormones may modu late the mechanism(s) underlying this motor asymmetry.