Below, for example, the rapid temporal alternation of two images results in transparency**
The transparency percept in the movie cannot be mediated by the mechanisms which create transparency in other situations, such as monocular static displays like the top one on the right. Many report that in this image they perceive bright tilted bars laying on top of dark bars. This is similar to what is perceived via temporal alternation above, but unfortunately there are limitations to the static technique, some of which can be overcome by the temporal alternation method. For example, using the conventional static method, one cannot present two colors in the same location without additional spatial context (i.e., an area where the colors do not overlap).
An explanation based on the static mechanism for the rapidly alternating display would posit that the two patterns sum internally and static cues subsequently allow decomposition into separate surfaces. To the contrary, summing the two patterns results in the bottom pattern on the right, which does not appear transparent. A simple nonlinearity before summation also is not the explanation, as the transparency works with a simple flickering light.
This phenomenon, among others, suggests that central stages of the human visual system tend to integrate over 100 msec or more of stimulation.
This phenomenon also provides a new way for graphics designers, artists, and engineers to present two things in the same location. For some more examples, click here.