The internal temporal dynamic of unconscious inhibition related to weak stimulus-response associations

Unconscious inhibition has generally been perceived to be dependent on stimulus-response (S-R) associations. Some research has shown that the inhibition related to strong associations increases with response latency to the target. Although this finding suggests that the inhibitory process may need time to unfold, its exact internal temporal dynamic remains to be elucidated. This study examined the role of spontaneous reaction time (RT) fluctuations on sensorimotor processes using letters (Experiments 1 and 2) and faces (Experiment 3), which are more ubiquitous in our environment and do not contain strong associations as stimuli in fixed and free-choice tasks. The results averaged across trials showed that there was no negative compatibility effect in either fixed or free-choice tasks. However, when trials were classified by their response latency, the results indicated that compatibility effects decreased and became negative with longer RTs in the fixed task. These results suggest that the internal temporal dynamic of unconscious inhibitory mechanisms related to fixed responses remains effective for stimuli that do not contain strong S-R associations.