Iring Koch

Control and interference in task switching--a review.

The task-switching paradigm offers enormous possibilities to study cognitive control as well as task interference. The current review provides an overview of recent research on both topics. First, we review different experimental approaches to task switching, such as comparing mixed-task blocks with single-task blocks, predictable task-switching and task-cuing paradigms, intermittent instructions, and voluntary task selection. In the 2nd part, we discuss findings on preparatory control mechanisms in task switching and theoretical accounts of task preparation. We consider preparation processes in two-stage models, consider preparation as an all-or-none process, address the question of whether preparation is switch-specific, reflect on preparation as interaction of cue encoding and memory retrieval, and discuss the impact of verbal mediation on preparation. In the 3rd part, we turn to interference phenomena in task switching. We consider proactive interference of tasks and inhibition of recently performed tasks indicated by asymmetrical switch costs and n-2 task-repetition costs. We discuss stimulus-based interference as a result of stimulus-based response activation and stimulus-based task activation, and response-based interference because of applying bivalent rather than univalent responses, response repetition effects, and carryover of response selection and execution. In the 4th and final part, we mention possible future research fields.

The role of inhibition in task switching: a review

The concept of inhibition plays a major role in cognitive psychology. In the present article, we review the evidence for the inhibition of task sets. In the first part, we critically discuss empirical findings of task inhibition from studies that applied variants of the task-switching methodology and argue that most of these findings— such as switch cost asymmetries—are ambiguous. In the second part, we focus on n-22 task-repetition costs, which currently constitute the most convincing evidence for inhibition of task sets. n-22 repetition costs refer to the performance impairment in sequences of the ABA type relative to CBA, which can be interpreted in terms of persisting inhibition of previously abandoned tasks. The available evidence suggests that inhibition is primarily triggered by conflict at selection of stimulus attributes and at the response level. Author Note

The Role of Response Selection for Inhibition of Task Sets in Task Shifting

Response selection in task shifting was explored using a go/no-go methodology. The no-go signal occurred unpredictably with stimulus onset so that all trials required task preparation but only go trials required response selection. Experiment 1 showed that shift costs were absent after no-go trials, indicating that response processes are crucial for shift costs. In Experiment 2, backward inhibition was absent after no-go trials. Experiments 3 and 4 demonstrated that response selection, rather than execution, causes backward inhibition. All 4 experiments showed effects of preparation time in go trials, suggesting that advance preparation must have also occurred in no-go trials. The authors concluded that inhibition of irrelevant task sets arises only at response selection and that residual shift costs reflect such persisting inhibition.

Cue-based preparation and stimulus-based priming of tasks in task switching

In this study, we investigated the interaction of three different sources of task activation in precued task switching. We distinguished (1) intentional, cue-based task activation from two other, involuntary sources of activation: (2) persisting activation from the preceding task and (3) stimulus-based task activation elicited by the task stimulus itself. We assumed that cue-based task activation increases as a function of cue—stimulus interval (CSI) and that task activation from the preceding trial decays as a function of response—stimulus interval. Stimulus-based task activation is thought to be due to involuntary retrieval of stimulus-associated tasks. We manipulated stimulus-based task activation by mapping each of the stimuli consistently to only one or the other of the two tasks. After practice, we reversed this mapping in order to test the effects of item-specific stimulus—task association. The mapping reversal resulted in increased reaction times and increased task shift costs. These stimulus-based priming effects were markedly reduced with a long CSI, relative to a short CSI, suggesting that stimulus-based priming shows up in performance principally when competition between tasks is high and that cue-based task activation reduces task competition. In contrast, lengthening the response—cue interval (decay time) reduced shift costs but did not reduce the stimulus-based priming effect. The data are consistent with separable stimulus-related and response-related components of task activation. Further theoretical implications of these findings are discussed.

Anticipated action effects affect the selection, initiation, and execution of actions.

This study investigated the impact of contingent action effects on response production. In Experiment 1 responses of varying intensity were initiated faster when contingently followed by auditory effects of corresponding rather than of noncorresponding intensity. This response–effect (R–E) compatibility influence was robust with respect to practice, and it was not due to persisting influences of preceding R–E episodes. These results support the conclusion that R–E compatibility reflects the impact of anticipatory effect representations in response production. Experiment 2 showed that anticipatory effect codes have an impact on early processes of response production (response selection) as well as on processes that immediately precede overt responding (response initiation). Finally, they also influence the way the actions are physically performed (response execution). The results support and specify ideo-motor theories of action control that assume movements to be controlled by anticipations of their sensorial effects.

Automatic and intentional activation of task sets.

Four experiments examined automatic and intentional activation of task sets in a switching paradigm. Experiment 1 demonstrated incidental task sequence learning that was not accompanied by verbalizable task sequence knowledge. This learning did not affect task shift cost and may be attributed to automatic task-set activation. In Experiment 2, both shift cost and learning effect increased when the response-cue interval was short, indicating the influence of residual, persisting activation of the preceding task set. In Experiment 3, learning disappeared with a long cue-stimulus interval (CSI), which resulted in a strong preparation effect. This preparation, however, reduced reaction time level but was not specific to task shifts. Finally, Experiment 4 showed that a within-subject C

Inhibitory processes in language switching: Evidence from switching language-defined response sets

We used language-defined response sets (digit names from 1 to 9 in different languages) to explore inhibitory processes in language switching. Subjects were required to switch between two (Experiment 1) or among three (Experiment 2) languages. In Experiment 1, we obtained a shift cost when subjects switched between their first and second language, between their first and third language, or between their second and third language. For each language pairing, the shift cost was larger for the relatively dominant language than for the nondominant language (i.e., asymmetric shift cost). In Experiment 2, we assessed inhibition of response sets as reflected in n-2 repetition cost (i.e., the difference between ABA and CBA language sequences). We discuss both effects with respect to inhibitory processes in language switching. The results suggest different functional characteristics of the processes underlying asymmetric shift cost and n-2 repetition cost.

Patterns, chunks, and hierarchies in serial reaction-time tasks.

Abstract The impact of relational structures (i.e., the systematicity of relations between successive items) on incidental sequence learning was investigated in a serial reaction-time (SRT) task while keeping constant the statistical structure. In order to assess the influence of relational structures in stimulus and response sequences separately, the strength of relational patterns in sequences of digits as stimuli and of keystrokes as responses was orthogonally varied. In Exps. 1 and 2, the variation of relational patterns was mainly effective in the keystroke sequence. In Exp. 2, in addition to the variation of relational patterns, the presentation of stimuli was delayed at serial positions that were incongruent with the relational structure. The results show that these incongruent pauses reduced the learning of strongly structured sequences of keystrokes but improved the learning of weakly structured sequences. Experiment 3 suggests that even higher-order relations between elementary patterns are utilized to accelerate responses. The data are interpreted as evidence for the impact of relational patterns, in addition to statistical redundancies, on the formation of chunks. Reasons are discussed for the finding that relational chunking was more pronounced in the keystroke than in the digit sequences.

Intention-based and stimulus-based mechanisms in action selection

Human actions can be classified as being either more stimulus-based or more intention-based. According to the ideomotor framework of action control, intention-based actions primarily refer to anticipated action effects (in other words response-stimulus [R-S] bindings), whereas stimulus-based actions are commonly assumed to be more strongly determined by stimulus-response [S-R] bindings. We explored differences in the functional signatures of both modes of action control in a temporal bisection task. Participants either performed a choice response by pressing one out of two keys in response to a preceding stimulus (stimulus-based action), or pressed one out of two keys to produce the next stimulus (intention-based action). In line with the ideomotor framework, we found intention-based actions to be shifted in time towards their anticipated effects (the next stimulus), whereas stimulus-based actions were shifted towards their preceding stimulus. Event-related potentials (ERPs) in the EEG revealed marked differences in action preparation for the two tasks. The data as a whole provide converging evidence for functional differences in the selection of motor actions as a function of their triggering conditions, and support the notion of two different modes of action selection, one being exogenous or mainly stimulus-driven, the other being endogenous or mainly intention-driven.

The role of external cues for endogenous advance reconfiguration in task switching.

Most studies of task-set switching rely on cuing paradigms, in which external cues indicate the upcoming task. The present study used an entirely predictable task sequence in a variant of the alternating-runs paradigm of Rogers and Monsell (1995). Preparation effects with purely internal memory cues were compared with those in another experimental group with additional external cues presented prior to the stimulus. External cues led to strongly reduced shift costs with prolonged preparation time. However, this effect was much smaller with internal cues only. To account for this differential effect of preparation time as a function of cue type, it is suggested that internal cues select the next task set, which is sufficient to perform the task. External cues additionally facilitate preparatory retrieval of task-specific stimulus-response rules. This account may also explain why incidental task-sequence learning based on internal cues did not reduce shift costs.