Reciprocal or independent hemispheric specializations: Evidence from cerebral dominance for fluency, faces, and bodies in right- and left-handers

Emma M. Karlsson, Leah Johnstone, David P. Carey

Abstract

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.