A Boundary of Ideomotor Control: Semantic Labels Bias Selection but Do Not Tune Motor Execution

Classic ideomotor theory proposed that actions can be automatically triggered by internally evoked representations of action-related features. This study examined whether motor execution in ideomotor action is more closely linked to lexical-semantic labels or to perceptually based evaluative content. In Experiments 1 and 2, participants responded to the Korean words "short" and "long" by pressing left or right keys. Semantic labels alone did not modulate keypress response duration (RD). However, in Experiment 2, task-irrelevant auditory tones of varying durations produced a graded increase in RD. Experiment 3 tested whether this modulation reflected physical duration itself or the evaluative processes involved in distinguishing and categorizing stimulus durations. Participants categorized six auditory stimuli as "short" or "long," with categorization difficulty manipulated by varying the distance between boundary stimuli. RD increased gradually across stimulus durations, but this effect was not stronger in the easy condition despite the larger physical spacing between tones. In addition, RD showed a category-related increase beyond what could be explained by physical duration alone. Together, these findings suggest that motor execution is influenced less by lexical-semantic labels than by perceptually based evaluative and categorical processing, helping to clarify the level of mental content that serves as an ideomotor cue.