Visual Illusions

gray illusion

Our lab is always on the lookout for new visual illusions. We recently discovered a motion illusion that we call the Shifty Shade Illusion (Schloss & Udawatta, VSS2014). As shown below, motion is perceived when the center bars within each bar-triplet are removed to reveal the background. The illusion is not due to surface similarity matching between frames because motion is still perceived when the deleted region lightness is most similar to the background lightness (see middle row, middle two columns below). It is also not due to reversed phi (Anstis, 1970) because it persists even when contrast polarity is constant across frames. However, motion is not perceived when dark bars are deleted on dark backgrounds (top row, right two columns) or light bars are deleted on light backgrounds (bottom row, left two columns). Whether or not motion is perceived is strongly predicted by a model that codes for changes the relative edge contrast between the central and flanking regions across frames. Our model outperforms the standard motion energy model (Adelson and Bergen, 1985) in predicting observers’ percepts of the Shifty Shade Illusion.