Association of Serum-Free-Testosterone Level with Hand Preference in Right-Handed Young Females

Abstract

The relationship between the degree of right-hand preference and serum free-testosterone level was studied in right-handed female subjects, who were 17–19 years old. It was assumed that free testosterone levels in serum of young female subjects would reflect the perinatal testosterone levels. Hand preference was assessed by the Edinburgh Handedness Inventory (Geschwind score, GS) and Waterloo Handedness Questionaire (Waterloo score, WS). The degree of the right-hand preference linearly and significantly increased as the serum free-testosterone level increased in the moderately right-handed (GS = < 70) subjects. There was only a marginally significant negative linear correlation between these parameters in the strongly right-handed subjects (GS > 70). These results only partly supported the testosterone hypothesis of cerebral lateralization that testosterone would slow the growth of the left cerebral hemisphere, reducing the degree of right hand preference. The results also suggested a trophic effect of testosterone especially on the left cerebral cortex in females. Activational effects of testosterone may also contribute to an increase in the degree of right-hand preference in right-handed young females.

Key Words:

• Handedness
• testosterone
• cerebral lateralization
• female
• brain