Modeling graded response congruency effects in task switching

The Effect of Aging on Response Congruency in Task Switching: A Meta-Analysis

OBJECTIVES

Response-congruency effects in task switching are the observed slowing of response times (RTs) for incongruent targets which afford more than one response (depending on task) in comparison to congruent stimuli that afford just one response regardless of the task. These effects are thought to reflect increased ambiguity during response selection for incongruent stimuli.

METHODS

The present study presents a meta-analysis of 27 conditions (from 16 separate studies) whose designs allowed investigation of age-related differences in response-congruency effects on RT.

RESULTS

Multilevel modelling of Brinley plots and state-trace plots showed no age-related effect on response congruency beyond that which can be explained by general age-related slowing.

DISCUSSION

The results add to the growing body of evidence of no age-related decline in measures of attention and executive functioning.

Same same but different? Modeling N-1 switch cost and N-2 repetition cost with the diffusion model and the linear ballistic accumulator model

In three task-switching experiments, we investigated the relationship of n-1 switch cost and n-2 repetition cost. N-1 switch cost is observed when participants are asked to switch from one classification task to another, e.g., from judging a digit as odd or even to judging a digit as smaller or larger than five. N-2 repetition cost is observed when participants are asked to switch among three tasks (thereafter called A, B, and C). This cost is observed when the task on trial n-2 is repeated in trial n (i.e., in task sequences like ABA) compared to when it is switched (i.e., in task sequences like CBA). So far, the n-1 switch cost is assumed to be caused either by reconfiguration processes or by episodic-memory inertia from the previously activated task-set. N-2 repetition cost is thought to reflect lingering inhibitory processes for resolving conflict among tasks. Whereas both views are integrated in some models, it is up to date unclear whether n-2 repetition cost is related to n-1 switch cost. To examine this relationship, we decomposed the processes underlying n-1 switch cost and n-2 repetition cost using a diffusion model analysis as well as a linear ballistic accumulator model. The results showed that n-1 switch cost reflects interference caused by the residual activation of the previous task set as indicated by slower evidence accumulation processes. In contrast, there were no consistent parameter modulations underlying n-2 repetition cost. These findings emphasize that different cognitive processes are involved in n-1 switch cost and n-2 repetition cost.

Does Task Activation in Task Switching Influence Inhibition or Episodic Interference?

N-2 repetition costs in task switching refer to slower responses to ABA sequences compared to CBA sequences, reflecting the persisting inhibition of task A across the ABA sequence. The magnitude of inhibition is thought to be sensitive to activation levels of interfering tasks. This is supported by larger n-2 repetition costs when the response-cue interval (RCI) is reduced: At short RCIs, a just-performed task is highly active when a new task is required, triggering more inhibition. However, recent work has shown that much of the n-2 repetition cost measures episodic interference, rather than inhibition. The current study addressed whether RCI manipulations influence inhibition or episodic interference. N-2 repetition costs were considerably reduced when episodic interference was controlled. Increasing the RCI led to equivalent reductions in the n-2 repetition cost for inhibition and episodic components of the cost, but for the former, the cost was entirely absent at longer RCIs.

Increased cognitive control after task conflict? Investigating the N-3 effect in task switching

Task inhibition is considered to facilitate switching to a new task and is assumed to decay slowly over time. Hence, more persisting inhibition needs to be overcome when returning to a task after one intermediary trial (ABA task sequence) than when returning after two or more intermediary trials (CBA task sequence). Schuch and Grange (J Exp Psychol Learn Mem Cogn 41:760-767, 2015) put forward the hypothesis that there is higher task conflict in ABA than CBA sequences, leading to increased cognitive control in the subsequent trial. They provided evidence that performance is better in trials following ABA than following CBA task sequences. Here, this effect of the previous task sequence ("N-3 effect") is further investigated by varying the cue-stimulus interval (CSI), allowing for short (100 ms) or long (900 ms) preparation time for the upcoming task. If increased cognitive control after ABA involves a better preparation for the upcoming task, the N-3 effect should be larger with long than short CSI. The results clearly show that this is not the case. In Experiment 1, the N-3 effect was smaller with long than short CSI; in Experiment 2, the N-3 effect was not affected by CSI. Diffusion model analysis confirmed previous results in the literature (regarding the effect of CSI and of the ABA-CBA difference); however, the N-3 effect was not unequivocally associated with any of the diffusion model parameters. In exploratory analysis, we also tested the alternative hypothesis that the N-3 effect involves more effective task shielding, which would be reflected in reduced congruency effects in trials following ABA, relative to trials following CBA; congruency effects did not differ between these conditions. Taken together, we can rule out two potential explanations of the N-3 effect: Neither is this effect due to enhanced task preparation, nor to more effective task shielding.

Task inhibition, conflict, and the n-2 repetition cost: A combined computational and empirical approach

Task inhibition (also known as backward inhibition) is an hypothesised form of cognitive inhibition evident in multi-task situations, with the role of facilitating switching between multiple, competing tasks. This article presents a novel cognitive computational model of a backward inhibition mechanism. By combining aspects of previous cognitive models in task switching and conflict monitoring, the model instantiates the theoretical proposal that backward inhibition is the direct result of conflict between multiple task representations. In a first simulation, we demonstrate that the model produces two effects widely observed in the empirical literature, specifically, reaction time costs for both (n-1) task switches and n-2 task repeats. Through a systematic search of parameter space, we demonstrate that these effects are a general property of the model's theoretical content, and not specific parameter settings. We further demonstrate that the model captures previously reported empirical effects of inter-trial interval on n-2 switch costs. A final simulation extends the paradigm of switching between tasks of asymmetric difficulty to three tasks, and generates novel predictions for n-2 repetition costs. Specifically, the model predicts that n-2 repetition costs associated with hard-easy-hard alternations are greater than for easy-hard-easy alternations. Finally, we report two behavioural experiments testing this hypothesis, with results consistent with the model predictions.

Learning a nonmediated route for response selection in task switching

Two modes of response selection--a mediated route involving categorization and a nonmediated route involving instance-based memory retrieval--have been proposed to explain response congruency effects in task-switching situations. In the present study, we sought a better understanding of the development and characteristics of the nonmediated route. In two experiments involving training and transfer phases, we investigated practice effects at the level of individual target presentations, transfer effects associated with changing category-response mappings, target-specific effects from comparisons of old and new targets during transfer, and the percentages of early responses associated with task-nonspecific response selection (the target preceded the task cue on every trial). The training results suggested that the nonmediated route is quickly learned in the context of target-cue order and becomes increasingly involved in response selection with practice. The transfer results suggested that the target-response instances underlying the nonmediated route involve abstract response labels coding response congruency that can be rapidly remapped to alternative responses, but not rewritten when category-response mappings change after practice. Implications for understanding the nonmediated route and its relationship with the mediated route are discussed.