Lateralised dual-task performance: the effect of muscular-repositioning.

In two experiments subjects performed tapping tasks requiring different degree of muscular repositioning while concurrently performing a speech task. In all concurrent speech conditions right-hand performance was disrupted more than left-hand performance, but the degree of this differential disruption did not alter as a function of the muscular repositioning requirements of the dual-tasks. It was concluded that rapid muscular repositioning does not appear to be the source of lateralised interference effects observed in concurrent task studies. However, it may be argued that some minimum level of repositioning is required, particularly if the differential effect reflects a lateralisation of "kind" rather than of "degree". This needs further research. One relevant factor proposed here which may alter the degree of lateralised effects is the degree of muscular effort required to perform each of the dual-tasks.