Abstract
Ambiguous visual information typically produces unstable visual perception. We have found that unambiguous tactile information about the direction of rotation of a globe significantly influences visual perception of a rotating globe (RG) whose 3D structure is ambiguous. Methods: The RG was created by projecting 240 moving white dots as if randomly distributed across the surface of a virtual globe rigidly rotating at 15 rpm about its vertical axis. Using optical techniques, the visual RG appeared in the same location as an unseen styrofoam globe covered with tiny bumps to simulate dots. This “tactile” globe (TG) was the same perceived size as the RG, and it could rotate at 15 rpm about its vertical axis in either a CW or CCW direction. Results: In one experiment observers tracked the direction of rotation of the RG for 1 minute while touching the TG as it rotated. The perceived direction of rotation of the RG was strongly biased by the direction of rotation of the TG. In a second experiment, the TG began to rotate at the same time that observers began to perceive the RG to be rotating in a given direction. When the rotation directions of the TG and RG were inconsistent, the perceived rotation direction of the RG changed to the opposite direction more quickly than in the condition in which the rotation directions were consistent. In a third experiment, we measured the initial perceived direction of rotation of the RG (1-sec presentation) after observers felt the TG rotating either CW or CCW with eyes closed, thereby engendering perception of rotation in one direction. In spite of the initial exposure to the rotating TG, the initially perceived direction of the RG was uninfluenced by the TG, in turn suggesting that results from Expts 1 and 2 are not attributable to imagery or to attention. Conclusion. Evidently the brain can draw on somatosensory evidence to influence the resolution of visual conflict.