| ISLE | Chapter 8
| Motion Aftereffect
The motion aftereffect, first discussed by Aristotle, is also known as waterfall illusion (Verstraten, 1996; Wade, 1996). An aftereffect is a sensory experience that occurs after prolonged sensory exposure to one stimulus that alters how we experience other stimuli after the prolonged exposure. Another way to observe this illusion at home is to watch the credits at the end of a movie without taking your eyes of the television screen. After watching the credits for two minutes, have a friend of family member hit the pause button. You will see an illusion of the movie credits moving up the screen even though you know the video is now stopped. Aristotle observed this by looking at non-moving surfaces after watching the downward motion of waterfalls.
To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.
On the Illustration tab,
click or touch (if you have a touch screen) any where on the grating to start the motion of the grating.
Stare in the middle of the grating while it moves. After the motion stops notice your perception of the still
grating. You can even look around the room at other objects to see if you experience the same effect.
On the Illustration tab, you can adjust these parameters:
Adaptation Duration: you can see how long the grating moves to create the motion aftereffect from 10 to 60 seconds.
Direction of the grating the grating is either vertical or horizontal.
Direction of Motion: the grating and move Forward (down for vertical gratings and to the right for horizontal gratings) or
Backward(up for vertical gratings or left ofr horizontal gratings)
Type of Grating: Squarewave: alternating black and white bars or Sinewave: fuzzy bars.
Grating Size: proportion of the vertical screen drawing area. So a grating size of 0.25 will have 4 bars on the screen.
Grating Speed how fast the grating moves in cycles/second. So a grating speed of 2 means that the grating will move the
distance of two cycles in a second (one black and one white bar = 1 cycle). Thus the larger the bar, the fater it moves
for the same grating speed.
At the top of the settings page is a Reset button. Pressing this button restores the settings to their default values.
Change the settings below to alter how the motion aftereffect illustration operates.