Gesine Dreisbach

Our cognitive system must manage two opposing demands: staying focused on one task (stability) and switching between tasks when needed (flexibility). Traditionally, a trade-off has been assumed between these two control modes. Recent studies questioned this idea. However, they do not consider that experimental manipulations can influence stability and flexibility at different levels of information processing and that a trade-off may only exist within the same level. We introduce a novel paradigm designed to investigate flexibility and stability at different levels of information processing (task vs. stimulus level). Participants switched between two categorization tasks while ignoring distractors. Distractors either came from the same (within-task) or the alternative task (between-task) and were either response-congruent or incongruent. In Experiments 1 and 2, participants categorized words superimposed on distractor images representing the generic response categories (task level interference). In Experiment 3, they categorized letters or digits flanked by distractor letters or digits (stimulus level interference). Reduced interference from between-task distractors compared to within-task distractors in Experiments 1 and 2 show shielding at the task level. At the stimulus level (Experiment 3) both distractor-types interfered to the same extent, indicating that the shielding against between-task distractors got bypassed by the automatic retrieval of learnt stimulus-response associations. Across all three experiments, shielding against between-task distractors in the previous trial improved subsequent performance, when the task repeated (i.e. it improved stability), but impaired performance, when the task switched (i.e. it impaired flexibility). This finding supports a trade-off between flexibility and stability at the task level.

In the task-switching paradigm, the most prominent measure are the switch costs indicating worse performance on task switches compared to task repetitions. Previous research showed that introspective RT estimations capture the switch costs. However, the meaning of these introspective switch costs is not yet well understood. They may simply reflect the immediate experience of an executed response or rely on abstract theory-based knowledge about task transitions ("task switches are difficult and take longer"). The present study investigated how introspective judgments are formed during task switching. In Experiment 1, we tested participants' awareness of task transitions as a prerequisite of theory-based knowledge. On a random subset of trials, participants had to indicate whether the current task repeated or switched relative to the previous trial. Judgments were collected with a short (1000 ms) and a long (5000 ms) time window to distinguish intuitive from deliberate decisions. As predicted, participants reliably recognized the transition even with a short time window. In Experiment 2, we reduced immediate experience-based knowledge by introducing NoGo trials where participants had to refrain from responding. Hence, required RT estimations most likely relied on theory-based processes. The results showed introspective switch costs even in NoGo trials suggesting that participants may use theory-based knowledge to inform their judgments although experience-based influences of covert responses may also play a role. Taken together, our findings provide novel insights into introspection during task switching contributing to a better understanding of how task-switching performance may relate to decision-making.

The list-wide proportion congruency effect describes how the congruency effect varies depending on the frequency of incongruent trials within a block. Specifically, the congruency effect is larger in mostly congruent (MC) blocks compared to mostly incongruent (MI) blocks. Research has shown that adaptation to these blocks does not change symmetrically when transitioning between them: moving from MC to MI leads to a rapid decrease in the congruency effect while transitioning from MI to MC results in little or no increase (Abrahamse et al., 2013). We aimed to investigate this asymmetric list shift (ALS) effect in a within-participants design where all participants experienced both transitions (MC-MI and MI-MC). Throughout Experiments 1–3 using a color-word Stroop task, we identified various forms of practice – including trial-type, stimulus-specific learning, general RT decrease, and a decrease in congruency effects over time (see Schmidt, 2016) – that can either facilitate or obscure the ALS effect, depending on the order in which participants experienced the transitions. In Experiment 4, using a face-name version of the Stroop task, where we minimized practice-related confounding factors by employing more complex stimuli and used a new stimulus set in the second transition, an ALS effect was observed regardless of the order of transition and for frequency-unbiased (i.e., 50% congruent) items. The role of practice effects and implications for the (in)-flexibility of control adaptations will be discussed.

Sociomotor theory – an extension of ideomotor theory – suggests that actions can also be represented in terms of the effects they elicit from others. But what if those others violate one’s action effect anticipations? Here, we introduce a novel joint goal-setting paradigm to investigate effects of co-actors’ occasional and overall unreliability on an individual’s goal selection. In a first step, the participant moved a target halfway from the bottom center to the top left or right corner of the computer screen. In the second step, the co-actor moved the target to its final left or right position. In a learning block, the co-actor always continued the participant’s target movements. In the test block(s), the co-actor produced congruent action effects in 50% (unreliable) vs. 80% (reliable co-actor) of the trials. Experiment 1 consisted of one (between-participants), Experiment 2 and 3 of two (within-participants) test blocks; in Experiment 3, the co-actor changed between blocks. Results of Experiments 1 and 3 reveal that participants repeated their corner choice more often after incongruent trials, but only when the co-actor was generally reliable. Implications in terms of sociomotor action control and joint action are discussed.