There are 6 stars here, 3 light and 3 dark. Fixate the red spot and adapt to the solid flickering stars (above) and flickering outlines (below). All six stars reappear, but you see only four of them. The outlines are as effective adaptors as the solid flickering stars.
As in the previous movie, adapting to the flickering outline circles makes the test disks disappear from view. Adapting circles flicker at 1, 2, and 4 Hz, and the rotating dashed circle is also an effective adaptor; clearly flicker rate is not crucial.
Selective adaptation. Fixate each red spot in turn (4 experiments). Adapting to the external outlines (top row) makes these outlines disappear, leaving only disembodied quadrants. Adapting to the internal crosses (bottom row) makes each star look like a uniform gray.
Left: You can’t adapt out the subjective contours of a Kanisza square. But right, you can adapt out the objective L-shaped corners: now the subjective square looks like a foggy blob or luminous haze.
While focusing on the central spot, view the flickering contours that superimpose onto the edges of the dark (left) and light (right) pyramids. During the test period, the pyramids now appear to have the same luminance as the background. Copies if the central dark and light square are presented above the pyramids for the sake of comparison.
First adapt to the flicker of the semicircle, presented superimposed on the left edge of the disk. Following flicker adaptation, not only has the left edge of the disk disappeared, but also a brightness gradient is apparent, making the disk appear like a half moon. In the absence of edge information on the left half of the disk, the brain appears to interpolate the brightness levels from the unadapted right edge to the background level.
This demonstration shows a test field of seven randomly arranged low-contrast annuli. All the annuli have the same size and shape so none of them pops out. But now adapt to the set of flickering circles, maintaining strict fixation on the small white square. When the test annuli re-appear, you will notice that one of them seems to have turned into a solid disk, which pops-out from the background annuli.