Abstract
We all experience repeated, reliable pairings of self-generated movements that result in visual sensations. Simply wave your hand in front of your open eyes and you will invariably perceive visual motion. Given this consistent pairing of kinesthetic and visual sensations, is it possible that experiencing only one of the paired sensations could give rise to the other?
We tested this possibility in three groups of blindfolded volunteers. People in Group A slowly waved their own hand in front of their face, those in Group B waved a cutout of a hand in front of their face, and Group C had the experimenter wave his hand in front of participants' blindfold. Participants rated resulting visual experience on a six-point scale ranging from “no visual experience” to “I perceive an outline of a moving hand.” Importantly, participants were given two successive test trials, and deceptive instructions explicitly led them to expect no visual sensation on one of the two trials. This created a bias against our proposed hypothesis. Nevertheless, people in Group A reported substantially higher visual ratings than those in Group C (main effect of group: F(2, 85)=5.72, p=0.005; planned t-test: t(55)=3.37, p=0.001). Ratings from Group B were between those from Groups A and C. Importantly, Group A participants who reported perceiving visual motion did so on both trials (t(27)=0.76, p=0.46) despite expecting no visual sensation on one of the trials. Preliminary data suggest that this illusory visual motion perception may be stronger when a dominant hand is used.
In conclusion, we show that self-generated movements are sufficient to yield visual sensations when executed in a way that typically results in the reliable pairing of vision and kinesthesia. We are currently exploring whether illusory visual motion is stronger in expert musicians, who have had years of training on intricate hand motions.