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Context, specifically the perceived figure or ground of an ambiguous form that surrounds a diagonal line segment, can influence the discrimination of that line segment even though the physical attributes of the context remain the same during figure-ground reversals. When the line segment was flashed on a region of the form seen as figure, discrimination was twice as accurate as when the line segment was flashed in isolation, and it was at least three times as accurate as when the line segment was flashed on that same region seen as ground.

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If some regions of a random-dotfieldare flickered, then the nonflickering areas appear to stand out in depth in front of the flickering regions. This perception of depth is optimal within a limited range of temporal frequencies. The average temporal luminance of the flickering and nonflickering regions was kept equal, so the depth segregation is not due to a luminance difference. In fact, depth is seen even when the average temporal luminance of the flickering regions is twice that of the steadily presented regions. The magnitude of perceiveddepth is affected by the percentage of luminance modulation: depth is maximal at 100% modulation and diminishes as the percent modulation decreases. We charted the tuning function using alternating flickering and nonflickering random-dot bars and found it to be similar to those of visual channels most sensitive to high temporal frequency.If areas of a filled visual field are flickered, the fMckering regions appear to lie in depth well behind the nonflickering regions (Wong & Weisstein, 1983a). When parts of a random-dot field were flickered so that the display consisted of alternating flickering and non flickering "bars" composed of dots, the nonflickering "bars" were seen to stand out in front of the flickering "bars."The nonflickering "bars" appear to form coherent rectangular shapes located in front of a background of flickering dots. The impression is not different from that of a row of figures contrasted against a flickering backdrop. The perceived depth effect reminds one of random-dot stereograms in which an area of dots may appear to float out in space in front of a background. Figure 1 is a representation of what the percept looks like to an observer. The flickering areas appear to stay at a constant depth behind the nonflickering areas rather than receding and approaching with the on-and-off cycle of the flicker. In other words, once the area is flickered at the appropriate temporal frequency, the flickering area remains steadily at a constant depth behind the nonflickering areas.The depth segregation produced by flicker-flickerinduced depth-is not due to a luminance difference between the flickering and nonflickering areas, since the average temporal luminance of all the regions was kept equal. It is also not dependent on the textural elements making up the visual field, since we obtained the effect with dots, horizontal lines, and vertical lines; nor does it depend on a specific configuration of the flickering and nonflickering regions, since we obtained this effect with "bars" made up of different textures and with concentric squares. The effect is not dependent on the density of dots filling the flickering and nonflickering regions, provided there is an adequate number of dots to define a region. Moreover, we found that a temporal frequency of about 6 Hz produced the greatest depth separation between the flickering and nonflickering areas, suggesting that visual channels responding pri-229