Uncorking the central bottleneck: Even novel tasks can be performed automatically.

Can people perform two novel tasks in parallel? Available evidence and prevailing theories overwhelmingly indicate that the answer is no, due to stubborn capacity limitations in central stages (e.g., a central bottleneck). Here we propose a new hypothesis, which suggests otherwise: people are capable of fully parallel central processing (i.e., bypassing the central bottleneck), yet often fail to do so, mainly due to preparation neglect. This preparation-neglect hypothesis was evaluated in four dual-task experiments pairing novel tasks (Task 1 and Task 2) using arbitrary stimulus-response mappings. Experiment 1, using a classic psychological refractory period (PRP) procedure, replicated the finding of dozens of previous PRP studies: none of the participants bypassed the bottleneck, instead exhibiting large dual-task interference on Task 2 (445 ms). In Experiment 2, the same dual-task PRP trials were randomly intermixed with single-task trials on Task 2, to boost preparation on that task. Here, nearly half the sample of participants bypassed the central bottleneck, exhibiting small dual-task interference on Task 2 (48 ms). Two additional experiments showed that initial practice does not by itself enable bottleneck bypassing, but boosting preparation of Task 2 (via intermixing single-task trials of Task 2) does. We conclude that, when properly prepared, people are capable of far more dual-task automaticity than was previously believed. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Bypassing the central bottleneck with easy tasks: Beyond ideomotor compatibility.

Maquestiaux, Lyphout-Spitz, Ruthruff, and Arexis (2020) demonstrated that ideomotor-compatible (IM) tasks (e.g., pressing the left key when an arrow points left) can operate automatically, entirely bypassing the central bottleneck that constrains dual-task performance. But is bottleneck bypassing a specific consequence of IM compatibility or is it due to task ease? To answer this question, we tested the automaticity of a task that was easy but not IM. The task was easy due to the high semantic compatibility between the stimulus and the response: saying "ping" when hearing "pong" and "pong" to "ping" in Experiment 1, saying "low" when hearing "high" and "high" to "low" in Experiment 2. We presented it as Task 2, along with a Task 1 that was not easy, due to the use of an arbitrary stimulus-response mapping. Single-task trials were randomly intermixed with dual-task trials and then used as baselines to assess dual-task costs and to simulate distributions of inter-response intervals (IRIs) predictive of bottleneck bypassing vs. bottlenecking. The results of both experiments provided converging evidence that the entire Task 2 bypassed the bottleneck on virtually all trials: very small dual-task costs, high percentages of response reversals, and a close match between the observed IRI distributions and that predicted by bottleneck bypassing. Neither ideomotor compatibility nor task speed (the semantic task was not particularly fast) explain these findings. We therefore propose that the key to bypassing the central bottleneck is the ease with which people can fully load the stimulus-response mapping into working memory.

Ideomotor compatibility enables automatic response selection.

A task is ideomotor (IM)-compatible when there is high conceptual similarity between the stimulus and the associated response (e.g., pressing a left key when an arrow points to the left). For such an easy task, can response selection operate automatically, bypassing the attentional bottleneck that normally constrains dual-task performance? To address this question, we manipulated the IM compatibility of a Task 2 that was performed concurrently with a non-IM-compatible Task 1, using the psychological refractory period procedure. Single-task trials, randomly intermixed with dual-task trials, served as a baseline against which to assess dual-task costs. The results indicated bottleneck bypassing (i.e., simultaneous response selection on both tasks) when Task 2 was IM-compatible, as evidenced by negligible dual-task costs on Task 2 (as well as on Task 1), very high percentages of response reversals, and weak correlations between Task-1 and Task-2 reaction times. These findings were supported by a fine-grained simulation analysis of inter-response intervals. We conclude that the perception of an IM-compatible stimulus directly activates the response code, which can then be selecting automatically, without recruiting central attention, consistent with A. G. Greenwald's (Journal of Experimental Psychology, 94, 52-57, 1972) original theory of IM compatibility.