Towards a taxonomy of inhibition-related processes: A dual-task approach
The ability to inhibit responses is key to controlled behavior and is commonly investigated with the stop-signal paradigm. The authors investigated how response inhibition is situated within a taxonomy of control processes by combining multiple forms of control within novel dual tasks. Response inhibition, as measured by stop-signal reaction time (SSRT), was impaired when combined with shape matching, but not the flanker task, and when combined with cued task switching, but not predictable task switching, suggesting that response inhibition may be weakly or variably impaired when combined with selective attention and set switching demands, respectively. Response inhibition was consistently impaired when combined with the N-back or directed forgetting tasks, putative measures of working memory. Impairments of response inhibition by other control demands appeared to be driven by task context rather than evoked control demands, as SSRT slowing was similar for trials where control demands were either present (e.g., task switch) or absent (e.g., task stay). These results were initially identified in a discovery sample and subsequently validated in a pre-registered analysis of a held-out sample of subjects (N = 33 and 33, respectively). Taken together, these results show that response inhibition processes are often impaired in the context of other control demands, even on trials where direct engagement of those other control processes is not required. This suggests a taxonomy of control in which response inhibition overlaps with related control processes, especially working memory.