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

Area of Science:

• Cognitive Neuroscience
• Psychology
• Human Perception

Background:

• Judging hand laterality, especially at unusual angles, can trigger a strong sensation of bodily movement without actual motion.
• Previous explanations often involve mental imagery, but a novel hypothesis suggests a cross-modal mechanism.

Purpose of the Study:

• To test the hypothesis that hand laterality perception involves multisensory binding between visual and proprioceptive inputs.
• To investigate if illusory feelings of movement are an aftereffect of intersensory recalibration.
• To differentiate this cross-modal binding mechanism from mental imagery accounts.

Main Methods:

• Two experiments were conducted manipulating selective attention and testing conditions designed to disrupt cross-modal binding.
• Participants judged the laterality of visually presented hands in various orientations.
• Illusory movement sensations were measured under different attentional and binding conditions.

Main Results:

• Experiment 1 demonstrated that manipulating selective attention could induce illusory movements in the incongruent hand, supporting the cross-modal binding hypothesis.
• Experiment 2 showed these illusions diminished when cross-modal binding was disrupted, confirming its necessity.
• The findings challenge imagery-based explanations for hand laterality perception.

Conclusions:

• Hand laterality perception relies on a multisensory binding process linking visual hand stimuli with the observer's own proprioception.
• Illusory bodily movement sensations are an obligatory consequence of this cross-modal recalibration.
• This mechanism provides a more accurate explanation than mental imagery for the observed phenomena.