Motion perception is the process of inferring the speed and direction of objects that move in a visual scene given some visual input. One explanation of motion perception involves a form of unconscious inference. That is, when we walk around or move our head in a particular way, we unconsciously expect that images of stationary objects will move on our retina. We discount such movement on the retina as due to our own bodily motion and perceive the objects as stationary. This site has a lot of examples of this if you want to take a look at it.