This illustration shows that another way to follow the racing car is to keep the eyes steady and to move just the head. This causes the image to project to exactly the same retinal location at each instant (assuming you move your head at precisely the correct angular velocity) as the car moves from right to left.

Once again, the percept is of the car moving from right to left. This percept will be the same as the two previous illustrations. How the brain distinguishes these different ways of following moving objects is the subject of much research. One more thing. Although I have presented three distinct ways of following moving objects, these illustrations are gross simplifications. In point of fact, when we follow moving objects we use various combinations of head and eye movements.

More information about movement perception is available.

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