Lateralized interference effects of concurrent verbal tasks on sequential finger tapping.

Twenty-four right-handed subjects concurrently performed both a sequential finger tapping task and a verbal task with or without visual guidance. The concurrent verbal tasks consisted of shadowing with vocalization and of memorizing without vocalization. The result showed that (1) both verbal tasks interfered with right hand tapping but not with left hand tapping, (2) lateralized interference was stronger in the shadowing than in the memorizing condition, and (3) performance did not differ under the visual and the non-visual guidance conditions. These data suggest that non-vocalized verbal tasks interfere with concurrent motor performance by the right hand, and that this lateralized interference effect is weaker than the effect produced by vocalized verbal tasks.