The backward crosstalk effect (BCE) in dual tasking means that characteristics of Task 2 of 2 subsequently performed tasks influence Task 1 performance. This observation indicates that certain features of the second response are already activated to some degree before the first response is selected. Therefore, the BCE challenges bottleneck models, which assume that Task 2 response selection does not begin until Task 1 response selection is finished. Instead, an extended model with a capacity-unlimited response activation stage prior to the bottleneck as the locus of the BCE was suggested. To determine the exact locus of the BCE within the stages of task processing, 5 experiments were carried out. Experiments 1 to 4 were psychological refractory period-like experiments with 3 subsequent tasks. A prebottleneck locus of the BCE was ruled out in Experiments 1 to 3 by using the locus of slack logic. Additionally, a postbottleneck locus of the BCE was ruled out in Experiment 4 by using the effect propagation logic. To further support this latter conclusion, Experiment 5 applied a go-signal manipulation. Taken together, the results of all 5 experiments strongly suggest that the BCE has its locus in the capacity-limited stage, which contradicts the widely accepted notion that a capacity-unlimited stage of response activation preceding response selection proper is the locus of the BCE. (PsycINFO Database Record

The Backward Crosstalk Effect (BCE) indicates that response features of Task 2 in a dual-task paradigm influence even Task 1 performance. However, it can be assumed that responses are represented with multiple features in the cognitive system. In this regard, Ideomotor Theory suggests action effects as one central response feature in human action control and an earlier study by Janczyk, Pfister, Hommel, and Kunde (Cognition 132: 30-43, 2014) already provided some evidence that action effects are a crucial determinant of the BCE. The present study aimed to further investigate which response features are critical for the BCE. Therefore, a crossed-hands manipulation was implemented in two experiments to examine whether the spatial position of the actual response and thus its associated action effects or the body-side of the effectors' anatomical connection determine the BCE. Analyses revealed that even when participants press a left response key with the right hand and vice versa, the usual BCE occurs. These results indicate that the BCE depends on spatial features of the action effects rather than on anatomical features and thus provide additional support for the assumption that action effects have an important influence on the BCE and on action control in general.