Vision, haptics, and attention: new data from a multisensory Necker cube

When looking monocularly at a three-dimensional (3-D) Necker cube two percepts alternate: a cube and a truncated pyramid. The latter is due to a depth reversal. We studied the effect of haptic information by having participants hold the cube with their hands and explore two of its vertices. Touch reduces the likelihood of the pyramid, consistent with a multisensory view of 3-D form perception. In addition, when the hand alternates between stationary and haptic exploration, the onset of the hand movement plays a crucial role in inhibiting reversals. A temporal analysis revealed that suppression occurred within a window lasting a few seconds from motion onset. In experiment 1, we monitored eye movements and instructed participants where to fixate. Although the percept does depend on which vertex is fixated, we ruled out a role of changes of fixation as a mediating factor for the effect of motion onset. In experiment 2, we introduced a change of position of the exploring hand as a new typ...