Action effect features, but not anatomical features, determine the Backward Crosstalk Effect: evidence from crossed-hands experiments.

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.

S1-R2 and R1-R2 Backward Crosstalk Both Affect the Central Processing Stage.

A frequent observation in dual-task experiments is that performance in Task 1 is influenced by conceptual or spatial overlap with features of Task 2. Such compatibility-based backward crosstalk effects (BCEs) can occur when overlap exists between the responses of two tasks-the R1-R2 BCE-or between the stimulus in Task 1 and the response in Task 2-the S1-R2 BCE. The present study investigated whether the S1-R2 BCE has a perceptual locus, and by implication, whether the two BCEs have a common processing locus or different ones. To this end, we applied the additive factors logic and manipulated the duration of the Task 1 perceptual stage. The results argue against a perceptual locus for both BCEs. As a possible explanation, we suggest that the R1-R2 BCE and the S1-R2 BCE have their locus within a capacity-limited central stage, but that they arise from different processes within this stage. The R1-R2 BCE influences Task 1 response selection, whereas the S1-R2 BCE influences Task 1 stimulus classification. A plausible though post-hoc model is presented within the Discussion.

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.

To prepare or not to prepare? When preparation of a response in Task 2 induces extra performance costs in Task 1.

In dual tasking, the no-go backward crosstalk effect (BCE) means that processing of Task 1 takes longer when Task 2 does not require a response (no-go trial) than when it requires a response (go trial). Thus, contrary to the usual observation, giving two successive responses counterintuitively reduces instead of increases performance costs for Task 1. Results from recent studies are in line with the notion that the no-go BCE reflects response inhibition, which is required to overcome an already prepared go response in Task 2, but which also spills over to motor execution in Task 1. No direct test of this hypothesis, however, has been carried out so far, and hence the present study was designed to fill this gap. The result of this study with n = 48 participants revealed that a no-go Task 2 impeded Task 1 performance when preparation of the Task 2 response was encouraged, but facilitated Task 1 performance when preparation of the Task 2 response was not encouraged.

The motor locus of no-go backward crosstalk.

A frequent observation in dual-task studies is the backward crosstalk effect (BCE), meaning that aspects of a secondary Task 2 influence Task 1 performance. Up to this point, 2 major types of the BCE were investigated: a BCE based on dimensional overlap between both stimuli and/or responses (the compatibility-based BCE), and a BCE based on whether Task 2 is a go or no-go task (the no-go BCE). Recent evidence suggests that the compatibility-based BCE has its locus inside the response selection stage. The available evidence for the locus of the no-go BCE is still mixed, however. To this end, the 3 experiments reported in the present study used an extended psychological refractory period (PRP) paradigm with 3 subsequent tasks. Applying the locus of slack logic in Experiment 1, the no-go BCE was not absorbed into the cognitive slack and, thus, a locus before response selection could be ruled out. Subsequently applying the effect propagation logic in Experiment 2 and 3, the no-go BCE arising in Task 1 was even inverted in Task 3. Because no propagation of the no-go BCE was observed, a locus before or in response selection could be ruled out. Thus, we conclude that the no-go BCE has its locus during motor execution. Because the no-go BCE and the compatibility-based BCE are located in different stages, we suggest that both types of the BCE do not share a common underlying mechanism. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Identifying the locus of compatibility-based backward crosstalk: Evidence from an extended PRP paradigm.

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

Action selection by temporally distal goal states.

In line with ideomotor theory, numerous response-effect compatibility (REC) studies have revealed evidence that action effects are anticipated prior to action initiation, as indicated by an REC effect: For example, a response is given faster when its effect occurs on the same rather than on the opposite side. So far, REC studies have only investigated immediate effects-that is, effects occurring immediately after the response is given. However, it may be argued that in everyday life many actions cause effects that do not occur immediately. Additionally, because actions can have more than one effect, desired effects occurring in the future may only be arrived at if fundamental effects are achieved first. In the present study, we investigated whether temporally more distal effects are anticipated in order to initiate actions, and how multiple, serially occurring effects are represented. To this end, a spatial REC paradigm was extended in such a way that a first, immediate effect (i.e., immediately following the response; E1) was followed 500 ms later by another visual effect (E2). An REC effect was only observed for the temporally more distal E2, and this result suggests that temporally more distal effects can also be anticipated during action selection.

Filled and empty motor reproductions of filled and empty intervals: Is there also a filled - reproduction illusion?

Previous studies have demonstrated that filled intervals are perceived as being longer than empty intervals of the same duration (i.e., the filled - duration illusion). In the present study, we asked whether the motor actions involved in filled and empty reproductions (a single continuous key press vs. two discrete key presses) would affect time estimates in a similar way. We hypothesized that reproductions of intervals of the same duration should be shorter for filled than empty reproductions (i.e., a filled - reproduction illusion). In two experiments, participants reproduced filled and empty intervals (ranging from 400 to 1,600 ms) using filled and empty reproductions. The results provided evidence for both kinds of illusions, even though the evidence was clearer for the filled - duration than for the filled - reproduction illusion. The present study demonstrates that in a situation in which both illusions work in concert, reproductions of the same interval can vary dramatically depending on the combination of interval and reproduction type.

A comparison of the psychological refractory period and prioritized processing paradigms: Can the response-selection bottleneck model explain them both?

Four experiments examined whether well-established phenomena from the psychological refractory period (PRP) paradigm are also observed in the prioritized processing paradigm, as would be expected from a common description of the 2 paradigms with the response selection bottleneck (RSB) model. Consistent with a generalization of the RSB model to the prioritized processing paradigm, Experiments 1 and 2 showed that this paradigm yields effects of SOA and stimulus discriminability analogous to those observed in the PRP paradigm. In Experiments 3 and 4, however, overall RTs and effect sizes differed between the PRP and prioritized processing paradigms in ways that are difficult to explain within the RSB model. Understanding the differences between these 2 paradigms offers considerable promise as a way to extend the RSB model beyond the domain of the PRP paradigm and to generalize our understanding of multitasking interference.

"Just do it when you get a chance": the effects of a background task on primary task performance.

Two experiments investigated multitasking performance with a new "prioritized-processing paradigm" in which participants responded only to a high-priority primary task when this task required some action, responding to a low-priority background task only when no action was required for the primary task. In both experiments, performance was worse on the primary task than on the same task performed in isolation, indicating that this attempt to give absolute priority to the primary task is not sufficient to protect it from multitasking interference. Multitasking interference was present for task-repetition trials as well as task-alternation trials, so the interference could not be completely explained as a task-switching cost. In addition, responses to the primary task were influenced by their compatibility with the responses associated with the stimulus for the background task, indicating that there was some activation of S-R associations within the background task even when this task did not require any response. The findings generalize a number of effects from the psychological refractory period and task-switching paradigms to the prioritized-processing paradigm, thereby providing hints as to the underlying mechanisms responsible for those effects. The "prioritized-processing paradigm" appears to have several desirable features for the study of multitasking interference.