Individual differences in lateralization: effects of gender and handedness.

Male and female left- and right-handers participated in 3 experiments designed to investigate 3 components of performance asymmetry in lateralized tasks. Experiment 1 used a consonant-vowel-consonant (CVC) identification task measuring quantitative differences in hemispheric abilities and hemispheric control and qualitative differences in hemispheric strategies. The quantitative data revealed that left-handers have a smaller performance asymmetry than do right-handers and that both groups have the same degree of increased accuracy when stimuli are presented bilaterally. Handedness affected the qualitative measures of men, not of women. Experiment 2 used nominal and physical letter-matching tasks with bilateral presentations and measured the flexibility of callosal function. The results suggest that left-handers have less flexible interhemispheric communication than do right-handers and show no effect of gender. Experiment 3 used a chair identification task indexing hemispheric arousal bias. Left-handers tended to have more aroused right than left hemispheres, whereas the distribution of right-handers was centered around 0 arousal bias. Intertask analyses revealed a relationship between arousal bias and metacontrol, where individuals with more aroused right hemispheres tended to use a right-hemisphere strategy in the bilateral condition of the CVC experiment. Intercorrelations between measures from the experiments revealed only a limited relationship between metacontrol patterns in the CVC task and a measure of callosal flexibility in the physical letter-matching task. The results are discussed in the context of the relationships between dimensions of hemispheric asymmetry.