What does lack of language lateralization signify? Evidence of fluctuating asymmetry rather than hemispheric equipoise on non-lateralized tasks

In a study of patterns of language laterality in left- and right-handers, Woodhead <i>et al</i>. (Woodhead ZVJ, Thompson PA, Karlsson EM, Bishop DVM. 2021 <i>R. Soc. Open Sci</i>. <b>8</b>, 200696. (doi:10.1098/rsos.200696)) noted that several tasks showed no bias to the left hemisphere in left-handed individuals. This might appear to suggest that these functions were mediated by the two hemispheres working together equally-what can be termed 'hemispheric equipoise'. Here, I consider an alternative possibility that individuals show lateral bias on these tasks, but the bias can occur to either the left or right-a form of fluctuating asymmetry. Further analysis of the distributions of data from individuals in Woodhead <i>et al.</i> is compared with simulated data. The pattern of results suggests that the impression of hemispheric equipoise may be an artefact of reliance on group data: even though the group mean does not differ from zero, a high proportion of individuals are biased to the left or right.