Speech lateralization assessed by concurrent task performance

A sequential button pressing task using either the left or the right hand while concurrently performing a speech task was investigated. Subjects with left-hemisphere speech representation, determined by a dichotic monitoring task showed a lateralized practice effect: left-hand performance improved with practice during the speech task, but right-handed performance did not. Subjects with right-hemisphere speech representation showed disruption of either hand with concurrent speech, and no lateralized practice effect. The results from this study suggest the mechanisms mediating speech perception and speech production may not always be concordantly lateralized. A discriminant analysis of the data showed that 93% of subjects could be correctly classified according to side of representation of speech perception given the performance measures on the concurrent tasks.