A minor role for hemispheric specialization in determining pseudoneglect: A pre-registered replication-extension study

Neurologically intact individuals display a mild asymmetry in spatial attention that can be measured during experimental spatial tasks such as line bisection. Although this phenomenon, known as pseudoneglect, is traditionally explained as the consequence of right hemisphere dominance for visuospatial attention, surmounting evidence suggests this is not its sole or even its most important determinant. For instance, a recent fMRI study in left-handers revealed that rare individuals with a reversed, left hemispheric dominance (LHDS, N = 23) also demonstrated left-sided pseudoneglect, although their spatial bias was less marked compared to typically lateralized controls (N = 40). The current study sought to replicate and extend these findings in a broader cohort of right-handers (N = 75) and left-handers (N = 181), while addressing methodological limitations of the original study. Contrary to the predictions of the hemispheric specialization account, pseudoneglect was not reversed in LHDS participants (N = 49). However, the pseudoneglect effect was reduced compared to controls with typical cerebral laterality (N = 207) due to a population-level randomization of pseudoneglect in the LHDS group. These results align with those of the original study, supporting a multifactorial interpretation of pseudoneglect, with hemisphere specialization as one among many determinants rather than being the predominant cause.