<span>I believe it is light, but this is kind of a confusing question. Technically there is a independent and dependent variable in the question. The variable being manipulated is light, and the earthwork activity depends on the light. </span>
True, just look at the weather channel on TV :)
This illusion is an example of what you called an INDUCED MOVEMENT. It is called an induced movement because animated neon signs seem to move even though there is no physical movement in them. Induced movement or induced motion is an illusion in which people tend look into it moving even it is really not moving.
