Effects of Lateralization of Language on Cognition Among Left-Handers.

Atypical language lateralization is associated with a different organization of the entire brain. However, it remains unknown whether this cerebral organization is linked to differences in cognitive task performance. In this study, several neuropsychological tests requiring fast processing speed were administered to left-handed participants, classified based on their language lateralization: left language dominance (n = 48), bilateral (n = 15), and right language dominance (n = 23). A factor analysis was conducted to derive three cognitive function dimensions: reading, articulation, and verbal reasoning; spatial processing; and interference/inhibition. The results showed that right language dominance was associated with poorer overall performance, particularly on tasks related to spatial processing, reading, articulation, and verbal reasoning. We conclude that the atypical development of language lateralization is accompanied by lower cognitive skills in tasks requiring speed of processing and interhemispheric connectivity.