Abstract
Previous studies demonstrated that human motor actions are not always monitored by perceptual awareness and that implicit motor control plays a key role in performing actions. In addition, appropriate evaluation of our own motor behavior is vital for human life. Here we combined a reaching task with a visual backward masking paradigm to induce an implicit motor response that is congruent or incongruent with the visual perception. We used this to investigate (i) how we evaluate such implicit motor response that could be inconsistent with perceptual awareness and (ii) the possible contributions of reaching error, external visual cues, and internal sensorimotor information to this evaluation. Participants were instructed, after each trial, to rate their own reaching performance on a 5-point scale (i.e., smooth-clumsy). They also needed to identify a color presented at a fixation point that could be changed just after the reaching start. The color was linked to the prime-mask congruency (i.e., congruent-green, incongruent-blue) in the practice phase, and then inconsistent pairs (congruent-blue or incongruent-green) were introduced in the test phase. We found early trajectory deviations induced by the invisible prime stimulus, and such implicit motor responses are significantly correlated with the action evaluation score. The results suggest the "conscious" action evaluation is properly monitoring online sensory outcomes derived by implicit motor control. Furthermore, statistical path analyses showed that internal sensorimotor information from the motor behavior modulated by the invisible prime was the predominant cue for the action evaluation, while the color-cue association learned in the practice phase in some cases biases the action evaluation in the test phase.