Which effect is responsible for trains seeming to be moving?
Answers
For example, when one is in a train at a station, and a nearby train moves, one can have the illusion that one's own train has moved in the opposite direction. Common sorts of vection include circular vection, where an observer is placed at the center of rotation of a large vertically-oriented rotating drum, usually painted with vertical stripes; linear vection, where an observer views a field that either approaches or recedes; and roll vection, where an observer views a patterned disk rotating around his or her line of sight. During circular vection, the observer feels like he is rotating and the drum is stationary. During linear vection, the observer feels like he has moved forwards or backwards and the stimulus has stayed stationary. During roll vection, the observer feels like he has rotated around the line of sight and the disk has stayed stationary.
After viewing continuous motion in the same direction for a long time, if you look at a stationary object, it appears to move in the direction opposite to the one you were viewing. This is sometimes called the "waterfall illusion" - if you look at a waterfall for a while, then look at a tree next to it, the tree appears to move upward. The demonstration above shows that this adaptation is local in the retina (to the right of where you were looking, you were adapting to rightward motion, to the left you adapted to leftward, and so on). We take this as evidence for the existence of neurons that are sensitive to motion and selective for the direction of motion, which adapt to the stimulus (analogous to color adaptation after-effects).