Handedness Does Not Impact Inhibitory Control, but Movement Execution and Reactive Inhibition Are More under a Left-Hemisphere Control

The relationship between handedness, laterality, and inhibitory control is a valuable
benchmark for testing the hypothesis of the right-hemispheric specialization of inhibition. According
to this theory, and given that to stop a limb movement, it is sufficient to alter the activity of the
contralateral hemisphere, then suppressing a left arm movement should be faster than suppressing
a right-arm movement. This is because, in the latter case, inhibitory commands produced in the
right hemisphere should be sent to the other hemisphere. Further, as lateralization of cognitive
functions in left-handers is less pronounced than in right-handers, in the former, the inhibitory
control should rely on both hemispheres. We tested these predictions on a medium-large sample of
left- and right-handers (n = 52). Each participant completed two sessions of the reaching versions
of the stop-signal task, one using the right arm and one using the left arm. We found that reactive
and proactive inhibition do not differ according to handedness. However, we found a significant
advantage of the right versus the left arm in canceling movements outright. By contrast, there were
no differences in proactive inhibition. As we also found that participants performed movements
faster with the right than with the left arm, we interpret our results in light of the dominant role of
the left hemisphere in some aspects of motor control.