Explaining dual-action benefits: Inhibitory control and redundancy gains as complementary mechanisms.

Abstract

Performing two actions at the same time usually results in performance costs. However, recent studies have also reported dual-action benefits: performing only one of two possible actions may necessitate the inhibition of the initially activated, but unwarranted second action, leading to single-action costs. Presumably, two preconditions determine the occurrence and strength of such inhibition-based dualaction benefits: (a) response set reductivity and (b) action prepotency. A nonreductive response set (given when all possible responses have to be kept in working memory) creates inhibitory action control demands in single-, but not in dual-action trials, and the ensuing inhibitory costs are proportional to the level of action prepotency (i.e., an action that is easy to initiate is hard to inhibit). Here, we set out to test this hypothesis by varying representational characteristics in working memory (namely response set reductivity and action prepotency) across four experiments. In Experiments 1 to 3, we compared (a) a randomized mode of trial presentation to (b) intermixed, but predictable fixed sequences of trial types and (c) a completely blocked mode of presentation. As expected, dual-action benefits were strongly present in Experiment 1, significantly reduced in Experiment 2, and absent in Experiment 3. This pattern of results matches our predictions derived from the assumption that differential inhibitory costs in single-action trials are the root cause of dual-action benefits. Crucially, however, the results of Experiment 4 (in which response conditions were only partially blocked) pointed to a secondary source of dual-action benefits that was inseparable from inhibition-based effects in previous experimental designs: semantic redundancy gains.

Dual-Action Costs and Benefits in a Uni-Modal Single-Onset Paradigm

“…In the present paper, we investigated the effects of single- versus dual-action demands in a simple, uni-modal, single-onset paradigm. As predicted (Prediction 1), we did not observe DABs, but rather significant DACs, in line with the assumption that DABs are based on differential inhibitory costs due to inhibitory coding (Raettig & Huestegge, 2021, 2023) and in line with Hypothesis 1: Inhibitory coding is only employed in contexts where inhibition is easy and cost-effective (i.e., when multi-modal responses reduce the potential for intra-modal interference and crosstalk). Furthermore, in line with Prediction 2, directional switches were associated with better performance than all other kinds of switches, supporting Hypothesis 2: actions appear to be coded as bundles of distinctive features (entailing that left-to-right and right-to-left switches simply require inverting the polarity of a “laterality” feature).…”

“…Various mechanisms have been proposed to explain such dual-action costs (DACs), for example, a bottleneck during response selection (Pashler, 1994), limited cognitive capacity that is shared between action-control processes (Meyer & Kieras, 1997; Tombu & Jolicoeur, 2003; Wickens, 2008), or crosstalk between concurrent or sequential task demands (Huestegge, 2011; Navon & Miller, 1987). However, we have recently observed the opposite effect in a number of studies where performance improved when participants had to execute two actions at the same time (dual-action benefits, DABs; Huestegge & Koch, 2014; Kürten et al, 2022; Raettig & Huestegge, 2018, 2021, 2023).…”

“…It has been argued elsewhere that DABs result from action inhibition – more specifically, deriving a single-action representation from a dual-action representation by removing one of the component actions (Huestegge & Koch, 2014; Raettig & Huestegge, 2018, 2021, 2023). The underlying assumption here is that under certain circumstances, single actions are actually cognitively represented in terms of what not to do (“inhibitory coding,” cf.…”

“…Importantly, our own experiments always made use of two response modalities (i.e., two effector systems), manual versus oculomotor (Huestegge & Koch, 2014; Kürten et al, 2022) and manual versus vocal (Raettig & Huestegge, 2018, 2021, 2023), respectively. Thus, there is correlational evidence suggesting that multi-modality may be a critical precondition for the occurrence of DABs, and there is a plausible causal mechanism, too: DABs are (at least partly) driven by differential inhibitory costs when single actions are coded inhibitorily, and inhibitory coding may only happen when the context allows for easy, cost-efficient action inhibition.…”

Preparing for simultaneous action and inaction: Temporal dynamics and target levels of inhibitory control.

“…Much as redundant stimulus information (e.g., in congruent trials of the Simon task, Simon & Rudell, 1967) can facilitate responding compared to a situation without such redundant information (Ulrich et al, 2015), executing one action might facilitate the execution of a concurrent, highly code-compatible action in dual-action trials but not in single-action trials. Still, dual-actions in the present study were easier to execute mainly due to the strong response commission bias in single-action trials and not due to more efficient (i.e., faster) dual-action (vs. single-action) execution (but see Raettig & Huestegge, in press for dual-action RT benefits).…”