Phantom contour
A phantom contour is a type of illusory contour. Most illusory contours are seen in still images, such as the Kanizsa triangle and the Ehrenstein illusion. A phantom contour, however, is perceived in the presence of moving or flickering images with contrast reversal. The rapid, continuous alternation between opposing, but correlated, adjacent images creates the perception of a contour that is not physically present in the still images. Quaid et al. have also authored a PhD thesis on the phantom contour illusion and its spatiotemporal limits (University of Waterloo) which maps out limits and proposes mechanisms for its perception centering around magnocellularly driven visual area MT (see also Quaid et al., 2005 on www.pubmed.com). Example One example of this illusion involves stimuli consisting of two similar frames, with uniform grey backgrounds: in one frame, the top half contains white dots and the bottom half contains black dots. A second frame contains the reverse of the first frame, in which the white dots of the first frame are replaced with black dots and the black dots are replaced with white dots. The rapid alternation between these two frames reverses the polarity of the dots, while keeping their positions static. At high