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Simple Summary This study focused on two characteristics of human motor control regarding an acquired skill. First, when performing a movement and generating errors, our movement is corrected based on the errors even if we do not have the intention to correct them. Second, our movement outcomes are always varied even when trying to perform the same movement repeatedly. Although previous studies have examined the relationship between the magnitude of movement correction and motor variability, their findings have been inconsistent. We hypothesized that the impact of motor variability might depend on the error size driving the movement correction and investigated the relationship between different error sizes. Data showed that larger motor variability led to a greater correction of movement when a large, not small, error occurred. The results provide further knowledge regarding the role that motor variability plays in motor learning. Previous studies have demonstrated the effects of motor variability on motor adaptation. However, their findings have been inconsistent, suggesting that various factors affect the relationship between motor variability and adaptation. This study focused on the size of errors driving motor adaptation as one of the factors and examined the relationship between different error sizes. Thirty-one healthy young adults participated in a visuomotor task in which they made fast-reaching movements toward a target. Motor variability was measured in the baseline phase when a veridical feedback cursor was presented. In the adaptation phase, the feedback cursor was sometimes not reflected in the hand position and deviated from the target by 0 degrees, 3 degrees, 6 degrees, or 12 degrees counterclockwise or clockwise (i.e., error-clamp feedback). Movements during trials following trials with error-clamp feedback were measured to quantify implicit adaptation. Implicit adaptation was driven by errors presented through error-clamp feedback. Moreover, motor variability significantly correlated with implicit adaptation driven by a 12 degrees error. The results suggested that motor variability accelerates implicit adaptation when a larger error occurs. As such a trend was not observed when smaller errors occurred, the relationship between motor variability and motor adaptation might have been affected by the error size driving implicit adaptation.

Imitation-inhibition training, requiring the inhibition of automatic imitative tendencies, has been proposed to enhance self-other distinction. Previous studies demonstrated that the training improves the ability of not only understanding others’ visual perspectives but also empathizing with them. We investigated the relationship between training and empathy in the recognition of others’ emotional states. All participants were trained on the first day and completed the self-reported empathy and facial expression recognition task the next day. This task consisted of a facial mimicry restricted block and an unrestricted block. The facial muscle activity and facial stimuli of participants were different in the restricted block because they had to hold chopsticks horizontally with their mouths, which interferes with facial mimicry. Consistent with a previous study, imitation-inhibition training increased self-reported empathy. Regarding recognition of facial expression, the performance of the control group declined due to interference with facial mimicry; on the other hand, the performance of the imitation-inhibition training group did not decline. These results suggest that imitation-inhibition training increases self-reported empathy and allows for a similar level of recognition of others’ emotional states, regardless of discrepancy between the condition of self and others.