Are subjects' perceptual asymmetries on auditory and visual language tasks correlated?: a meta-analysis.

A number of studies have investigated the correlation between subjects' perceptual asymmetries on auditory and visual language tasks. With few exceptions, these studies have found low, nonsignificant correlations between the two types of perceptual asymmetries. However, variations in subjects' perceptual asymmetries on these tasks reflect not only individual differences in language lateralization but also several extraneous variables (e.g., random errors, individual differences in left-right attentional biases). Thus, low correlations between the two types of asymmetries may reflect "masking" by these extraneous variables rather than a "true" cross-modal dissociation. Consistent with this view, a meta-analysis of prior studies revealed a small, but significant correlation between the two types of asymmetries for left-handers. The correlation was nonsignificant for right-handers, presumably reflecting stronger attenuation caused by limited variability in language lateralization in this group. Possible factors mediating significant correlations between the two types of perceptual asymmetries include certain language processes shared by the two types of tasks, cross-modal consistency in individual differences in lateralization of certain modality-specific language processes, and cross-modal consistency in individual differences in left-right attentional biases.