Reciprocal or Independent Hemispheric Specializations: Evidence From Cerebral Dominance for Fluency, Faces, and Bodies in Right- and Left-Handers

Objective : There are distinct cortical regions that respond preferentially to human faces and bodies. It is generally accepted that these face- and body-selective regions are lateralized to the right hemisphere, but unknown how frequently these biases occur or if they are lateralized in a complementary fashion to language processing. Method : Functional magnetic resonance imaging (fMRI) was used to examine face and body lateralization in two samples of right-handers (n's = 31 and 18) and left-handers (n's = 43 and 24) with "typical", left hemisphere, language dominance to examine the frequency of these biases. Crucially, we also recruited individuals with "atypical," right hemisphere, language dominance (n's = 17 and 10) to examine complementarity with language. Results : Language typical right-handers had consistent population-level and average right-sided biases for face and body perception. Language typical left-handers had population-level biases for faces in Sample 2, but not Sample 1; and for bodies in Sample 1 but not Sample 2. Language typical left-handers were, on average, right-lateralized for faces in both samples, but right-lateralized for bodies in Sample 1 only. Language atypicals did not have a population-level bias for body or face perception, and were, on average, left-lateralized for faces in Sample 1, but not in Sample 2. Language atypicals were not lateralized for body perception. Conclusions : These results add to the growing literature which suggests that many right hemisphere processes are not lateralized in a fully complementary fashion to language. Left-handers seem to have more varied lateralization patterns even when language dominance is controlled for. Public Significance Statement This research demonstrates differences in patterns of complementary brain processes across the hemispheres in left- and right-handers. We also show that the rare kind of brain dominance for language is not associated with specialization of body and face processing to the non-language hemisphere as a matter of routine. These data are important for models which claim unusual hemispheric dominance in individuals with neurodevelopmental conditions, as well as for our understanding of the nature of brain asymmetries in left-handed people.