The Contextual Specificity of Pausing: Interpreting Electromyographic Partial Responses During Action Cancellation and Attentional Capture

Abstract A recent theoretical model of action stopping posits that the reactive cancellation of movement is underpinned by two dissociable processes: a rapid, involuntary “pause” that transiently suppresses motor output, and a slower, voluntary, suppression/retuning of motor output. Notably, the pause process has been posited to generalise broadly to infrequent and salient stimuli (irrespective of whether they bear an imperative to stop) and to be observable as suppression in electromyographical (EMG) recordings. Over two experiments (N = 24 in each), participants completed standard stop signal and flanker tasks, and novel flanker task variants, where flanking arrows occurred infrequently (33% of trials), with or without a delay relative to the central imperative stimulus, or coincident with a stop signal. Presenting flankers infrequently specifically increased slowing to incongruent trials, with no effect on congruent or neutral trials (relative to a condition with flankers on every trial), and only after at least three preceding trials with no flanking stimuli. When flanker stimuli were presented infrequently, and after a delay, they did not reliably elicit suppression of EMG. These results highlight the contextual specificity with salient infrequent stimuli elicit behavioural slowing and EMG suppression, challenging the notion of a broadly generalisable pause process. EMG analysis also revealed that stop signals which occurred synchronously with flanker arrows resulted in faster stopping than stop signals without flanker arrows, highlighting the sensitivity of the stopping process to stimulus features. Collectively, these results challenge recent interpretations which attribute covert muscle activation to specific neural mechanisms. Competing Interest Statement The authors have declared no competing interest. Footnotes Some disambiguation was provided for part of the results