[Auditory lateralization in monozygotic twins: a study with dichotic consonant-vowel recall]

Auditory lateralization was examined in 21 monozygotic twin pairs (n = 42) and 52 singletons (healthy volunteers). Nine of the twin pairs were discordant for handedness, and 12 consisted of concordantly right-handed persons. All subjects were studied with a German dichotic consonant-vowel recall test using the syllables /ka/, /ta/, /pa/, /ga/, /da/ and /ba/ as stimuli. There was (i) a marked right-ear advantage in right handed singletons (as expected), (ii) no significant ear advantage among monozygotic twins (neither among those concordant nor those discordant handedness), and (iii) no relation between the direction of ear advantage within twin pairs. These data suggest that auditory lateralization is largely determined nongenetically.