Illusory motion capture and release in rotating 3-D figure in humans.

An illusory bar emerges in a cleft between two opposing gratings. When the gratings rotated around the vertical axis in three-dimensional (3-D) space, the illusory bar was seen either (i) rotating with the inducing gratings or (ii) as a stationary and opaque tape located in front of gratings. This illusion seems to be caused by the different temporal dynamics of the illusion and its inducers, especially by the slower extinction rate for the illusory bar than its inducers. The illusion is a psychophysical demonstration of an illusory figure becoming spatially and temporally loose from its inducers, suggesting that they are processed separately in the brain. This indicates that illusory figures are not only by-products of normal vision but have their own important function.