A large-scale estimate on the relationship between language and motor lateralization

Abstract

Human language is dominantly processed in the left cerebral hemisphere in most of the population. 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. 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. Overall, we found a right ear advantage indicating typical left-hemispheric language lateralization in 82.1% of the participants. 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. Here, only 0.4% of the variance in language lateralization were explained by handedness. We complemented these analyses with Bayesian statistics and found no evidence in favor of the hypothesis that language lateralization and handedness are related. 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 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. 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. 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.

Dichotic Listening Performance and Interhemispheric Integration After Administration of Hydrocortisone

“…We partly con rmed our initial hypotheses since there was indeed no effect of cortisol increases on FHAs as measured via an emotional and verbal dichotic listening task in line with the ndings ofBerretz, Packheiser, et al (2020). Previous studies byBrüne et al(2013) andStanković and Nešić(2020) found effects of stress on lateralized face perception.…”

How Asymmetries Evolved: Hearts, Brains, and Molecules

“…Handedness, too, is effectively a cerebral asymmetry, not a manual one, and is commonly associated with the left-hemispheric dominance for speech. The correlation is in fact much weaker than previously assumed [40]. Some 95 percent of right-handers are left-cerebrally dominant for language, but so are 70-80 percent of left-handers [41].…”

Handedness Development: A Model for Investigating the Development of Hemispheric Specialization and Interhemispheric Coordination

“…Therefore, if handedness is to be related to hemispheric specialization for speech production, we need to focus on differences in hand preference or skill, not narrative identity or questionnaire scores [19]. For example, Packheiser et al [20] found no association between lateralization for language (as measured by ear differences in dichotic listening) and handedness for over 1500 adults. Handedness was measured by the EHI using four common classification schemes, including one based on latent class analysis.…”

“…In part, this is because we lack suitable models of the distribution of each and therefore have no way of assessing whether their joint probability occurs by chance. For example, dichotic listening data from 1554 individuals revealed that over 82% of participants had left-hemisphere language comprehension [20]. However, no relation was identified with handedness (as measured by common questionnaire results), leading the authors to conclude that it is unlikely that handedness and language lateralization are associated.…”