Telling the right hand from the left hand: multisensory integration, not motor imagery, solves the problem.

Judging the laterality of a hand seen at unanticipated orientations evokes a robust feeling of bodily movement, even though no movement is produced. In two experiments, we tested a novel hypothesis to explain this phenomenon: A hand's laterality is determined via a multisensory binding of the visual representation of the seen hand and a proprioceptive representation of the observer's felt hand, and the felt "movement" is an obligatory aftereffect of intersensory recalibration. Consistent with the predictions implied by such a cross-modal mechanism, our results in Experiment 1 showed that manipulating observers' selective attention can evoke illusory feelings of movement in the "wrong" hand (i.e., the hand whose laterality does not match that of the stimulus). In Experiment 2, these illusions were readily extinguished in conditions in which binding was predicted to fail, a result indicating that cross-modal binding was necessary to produce them. These results are not explained by imagery, a mechanism widely assumed to account for how hand laterality is identified.