Exploring the Limits and Sources of Sequential Modulations in Backward Crosstalk

Dual tasking typically comes with performance costs in at least 1 of the 2 tasks relative to their performance as single tasks. In addition, compatibility relations between stimuli and responses can affect task performance. We here focus on the (response-related) backward crosstalk effect (BCE): Response times in Task 1 are shorter if the responses in Task 1 and 2 share compatible rather than incompatible spatial features. Interestingly, the BCE shows a sequential modulation: It is larger after compatible Trials N – 1 than after incompatible Trials N – 1, although the underlying reasons remain unclear. We report 2 experiments. Whereas Experiment 1 replicated the sequential modulation, Experiment 2 did not when effector combinations changed from trial to trial. These results suggest that sequential modulations of the BCE do not occur when the context of a trial changes to a sufficient degree. Additional results from applying a diffusion model attribute the sequential modulation to less Task 2 response activation after incompatible Trials N – 1. This result offers insights into the mechanisms underlying task shielding in dual tasking.