Androgenic influences on neural asymmetry: Handedness and language lateralization in individuals with congenital adrenal hyperplasia.

This study tested the hypothesis that prenatal androgen levels influence hand preferences and language lateralization, two manifestations of neural asymmetry. Participants were individuals with congenital adrenal hyperplasia (CAH, a genetic disorder that results in excess adrenal androgen production beginning prenatally) (40 females; 29 males) and their unaffected relatives (29 females; 30 males) who ranged in age from 12-45 years. The Edinburgh-Crovitz Inventory and the performance of five simple tasks (the Handedness Activities Test) were the measures of hand preferences, and a dichotic listening task composed of consonant-vowel nonsense syllables was the measure of language lateralization. No sex differences were observed among relative controls in hand preferences or language lateralization. Male participants with CAH were less consistently right-handed for writing than unaffected male relatives, when those who had been forced to switch writing hands from left to right were considered with left-handers as being not consistently right-handed. There were no other significant differences between individuals with CAH and unaffected relatives. These results do not support the hypothesis that prenatal androgens influence language lateralization, nor do they support the Geschwind-Behan-Galaburda model that posits a key role for testosterone in the development of cognitive problems in males, secondary to changes in hemispheric development and cognitive lateralization. Hormonal influences on handedness, although not always consistent, may be more likely. However, given that sex differences in both language lateralization and handedness are small, it is possible that limited sample size precludes the detection of consistent group differences.