Editing Motion perception (section)

==The aperture problem==
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[[Image:aperture problem animated.gif|thumb|275px|The aperture problem. The [[grating]] appears to be moving down and to the right, [[perpendicular]] to the orientation of the bars. But it could be moving in many other directions, such as only down, or only to the right. It is impossible to determine unless the ends of the bars become visible in the aperture.]]
The motion direction of a contour is ambiguous, because the motion component parallel to the line cannot be inferred based on the visual input. This means that a variety of contours of different orientations moving at different speeds can cause identical responses in a motion sensitive neuron in the visual system.