Sequential modulation of backward crosstalk and task-shielding in dual-tasking.

Abstract

In dual-task studies, Task 1 performance is often improved when Task 2 requires a spatially compatible response (i.e., 1 on the same side)-the backward crosstalk effect (BCE). This BCE is taken as evidence that at least some of the tasks' central processing related to response selection occurs in parallel, and the size of the BCE has been interpreted as an index of how well Task 1 is shielded against influences from the concurrent Task 2 processing. In 3 experiments, it is investigated whether the compatibility status of the previous trial influences the BCE similar to the Gratton effect observed for conflict tasks. In all experiments, the BCE was large after a compatible trial but absent (or reversed) after an incompatible trial, thus a Gratton-like sequential modulation of the BCE. This result suggests rapid bottom-up adjustments as a consequence of just-experienced incompatibility of responses. One explanation is that the degree of allowed parallel processing during Task 1 response selection is adjusted according to recent experience.