Lateral differences in schematic face encoding during dual-task performance with increasing levels of difficulty.

20 normal, right-handed, familial dextral men performed (a) unimanual finger tapping, (b) encoding of schematic faces at three levels of difficulty (3, 5, and 7 faces), (c) verbal production, (d) concurrent tapping and verbal production, and (e) concurrent tapping and face encoding. Subsequent recognition of faces was disrupted more by concurrent left-hand tapping than by concurrent right-hand tapping, supporting both the hypothesis that the right hemisphere mediates face encoding in adults and Kinsbourne and Hicks' (1978) "functional cerebral distance principle." Left- and right-hand tapping rate and variability were not asymmetrically affected by either verbal production or face encoding. While there was an increase in generalized interference effects on face encoding, the degree of asymmetry of the interference remained constant. In addition, as the difficulty of the memory task increased, variability of tapping rate decreased. This was discussed in terms of attention and automatic motor programming.