dichotic listening task 2006 schizophrenia

classification of individuals into for example left- and right-handers as well as those with a left- and right-hemispheric dominance in language processing. Several studies investigated the relationship between language lateralization and handedness on the categorical level, i.e. Since speech impairment syndromes such as aphasias in patients with unilateral brain damage were found to be less severe in left-handers 7, it was assumed that these two asymmetries are to some extent associated and may even share a common genetic foundation 8, 9. A number of studies have demonstrated that about 85–90% of the population shows a left-hemispheric dominance in several language-related tasks 2, 3, 4, 5, 6. One of the best known functional hemispheric asymmetries is the lateralization of the human language system 1. Furthermore, sex differences seem to be present in language lateralization when the power of the study is adequate suggesting that endocrinological processes might influence this phenotype. Overall, these findings indicate that the direct associations between language lateralization and motor asymmetries are much weaker than previously assumed with Bayesian correlation analyses even suggesting that they do not exist at all. We also found differences in the extent of language lateralization between males and females with males exhibiting higher dichotic listening LQs indicating more left-hemispheric language processing. Footedness LQs were not correlated with dichotic listening LQs, but individuals with atypical language lateralization also exhibited higher rates of atypical footedness on the categorical level.

We complemented these analyses with Bayesian statistics and found no evidence in favor of the hypothesis that language lateralization and handedness are related.

Here, only 0.4% of the variance in language lateralization were explained by handedness. While we found significantly more left-handed individuals with atypical language lateralization on the categorical level, we only detected a very weak positive correlation between dichotic listening lateralization quotients (LQs) and handedness LQs using continuous measures. Overall, we found a right ear advantage indicating typical left-hemispheric language lateralization in 82.1% of the participants. In this study, we comprised data from 1,554 individuals sampled in three previous studies in which language lateralization measured via dichotic listening, handedness and footedness were assessed.

While several studies have suggested that there are higher rates of atypical right-hemispheric language lateralization in left-/mixed-handers, an accurate estimate of this association from a large sample is still missing. Human language is dominantly processed in the left cerebral hemisphere in most of the population.

Dichotic listening task 2006 schizophrenia