Dual-task interference in left-handed subjects: hemispheric specialization vs manual dominance

Thirty-six left-handed subjects performed a dichotic listening task and two concurrent (verbal plus finger-tapping) tasks. Baseline tapping scores revealed both left- and right-hand dominance within left-handed subjects. Moreover when subjects were categorized as consistent or inconsistent for 'sidedness advantage' (e.g. consistent = same side for dominant hand and ear advantage), it was shown that the dual-task interference effects found on the concurrent tapping tasks were due to both hemispheric specialization and manual dominance.