Action planning modulates perceptual confidence through action monitoring processes

Abstract Dominant models of metacognition suggest that sensory information quality determines perceptual confidence, but recent accounts propose that motor signals also affect confidence judgments. In this study, we investigated the impact of motor planning of perceptual responses on decision confidence, testing two hypotheses. The “fluency hypothesis” suggests that ease of motor response selection and preparation enhances confidence. In contrast, the “monitoring hypothesis” posits that increased action monitoring during response selection boosts confidence, potentially counteracting response fluency. In three pre-registered experiments, participants reported the orientation of a stimulus and indicated their confidence in their response. A cue induced action planning that was either congruent or incongruent with the response side used to report the stimulus orientation. Across experiments, we consistently observed higher confidence when participants prepared spatially incongruent actions compared to congruent ones, regardless of response accuracy. In the third experiment, electroencephalography (EEG) revealed an increased fronto-central P2 amplitude for incongruent actions, suggesting that incongruent action planning heightened early attentional resources needed to resolve response conflict. Incongruent action plans also modulated post-response ERPs at centro-parietal channels (e.g., Pz), typically linked to confidence and error monitoring. These findings align with the “monitoring hypothesis” suggesting that the degree of action monitoring during response selection modulates retrospective decision confidence. Public Significance Statement While virtually every decision we make leads to an action, the role of motor processes in decision making has been largely neglected. Our results show that retrospective confidence in a perceptual discrimination task is boosted when the motor execution is spatially incongruent with motor preparation, independently of the correctness of the response. Electroencephalography recordings indicate that this effect could be explained by a larger involvement of early attentional resources related to action monitoring, which has an impact on confidence computations. Taken together, these results suggest that action planning information might trigger monitoring mechanisms susceptible to alter retrospective confidence in our decisions, implying that motor processes are not only the output, but also an input of the decision mechanisms.