Investigating multidimensionality of language lateralisation in left and right handed adults: an update on Woodhead et al. 2019

A previous study we reported in this journal suggested that left and right handers may differ in their patterns of lateralisation for different language tasks. However, it had too few left handers (N=7) to reach any conclusions. For this update paper, further participants were added to the sample to create separate groups of left (N=31) and right handers (N=43). Two hypotheses were tested: 1) that lateralisation would be weaker at the group level in left than right handers; and 2) that left handers would show weaker covariance in lateralisation between tasks, supporting a two factor model.All participants performed the same protocol as in our previous paper: lateralisation was measured using functional transcranial Doppler sonography during six different language tasks, on two separate testing sessions. The results supported hypothesis 1, with significant differences in laterality between groups for four out of six tasks. For hypothesis 2, structural equation modelling showed that there was stronger evidence for a two factor model in left than right handers; furthermore, examination of the factor loadings suggested that the pattern of laterality across tasks may also differ between handedness groups. These results expand on what is known about the differences in laterality between left and right handers.