The dual task paradigm: speech dominance or manual dominance?

Two hundred and sixty monolinguals divided into subgroups based on gender, handedness, and familial left-handedness, were given a concurrent task, verbal-manual interference paradigm. The primary purpose of the study was to test whether the dual task interference effects were more related to hemispheric speech or manual dominance factors. The dominant hand, regardless of handedness, underwent relatively more tapping interference than the nondominant hand. The obtained results seriously question the basic assumptions underlying the interpretation of the dual task paradigm as an assessment index for hemispheric language lateralization. A possible explanation of this result that is in keeping with known hemispheric language representation proportions in left-handers is offered based on left hemisphere ipsilateral control of the left hand.