Select occluder type:

Real occluders
Virtual occluders

What to observe:

Theoretical significance

The fact that we experience motion from two stationary objects flashing on and off is sometimes explained by saying that they stimulate an elementary motion detector in much the same way as a moving object. However, this can not explain why the motion of the red square is lost in the conditions with additional occluders. It is particularly difficult to see why an elementary motion detector should react differently to the version with the virtual occluders, because here the stimulus is absolutely identical in the regions close to the red squares. An alternative, more convincing explanation is that the brain seeks an interpretation that explains the events in the stimulus. In the standard condition, the motion interpretation explains the appearance and disappearance of the red square at different positions. In the two conditions with occluders, the motion of the occluders provides an explanation for the disappearance and apparence of the occluders, and at the same time for the disappearance and appearance of the red square. Hence, the interpretation that the red squares are moving is not necessary.