Two types of backward crosstalk: Sequential modulations and evidence from the diffusion model.

In multitasking, the backward crosstalk effect (BCE) means that Task 1 performance is influenced by characteristics of Task 2. For example, (1) RT1 is shorter when the two responses are given on the same (compatible trial) compared with opposite sides (incompatible conflict-trial; compatibility-based BCE), and (2) RT1 is longer when Task 2 is a no-go relative to a go task (no-go BCE). We investigated the impact of recently experienced trial and conflict history on the size of such BCEs. Similar to the Gratton effect in standard conflict tasks, clear sequential modulations were observed for the two kinds of BCEs, which were present following (1) compatible trials and (2) go-trials and inverted following (1) incompatible and (2) no-go trials. Furthermore, recent evidence from mental chronometry studies suggests that the compatibility-based BCE is located inside the response selection stage, while the no-go-based BCE arises in motor execution. Against this background, a diffusion model analysis was carried out to reveal the reason(s) for the sequential modulations. As expected, for the compatibility-based BCE, changes in drift rate explain the sequential modulations, but for the no-go BCE changes in non-decision time are important. The present results indicate that both BCEs not only differ fundamentally in their underlying processes, but also in the way cognitive control is adjusted.