Motion Aftereffect (Waterfall Illusion)
Fixate on the central cross during the motion and watch the cycle at least three
times. Observe the motion aftereffect in the resting figure (the Buddha of
Kamakura). [There is a more flashy version on the next page.] The "Fullscreen"
mode (lowest button) can enhance the effect, but might be too slow depending on
your screen size and computer speed.
[Should nothing move here, try the older Flash version.]
You may also try to cover one eye, adapt over 3 cycles and then test with the other
eye (for this, you will need to stop the movie at the right point…). Well, how strong
is your “interocular transfer”?
This is often explained in terms of “fatigue” of the class of neurons encoding one
motion direction. It is probably more accurate to interpret this in terms of adaptation
or “gain control”.
We use the motion aftereffect in combination with EEG recordings as a tool to analyse
the human motion system (→motion projects). For a more detailed
explanation and a neat demo of the “waterfall effect” see George Mather’s MAE page.
Sources
Aristotle “De Somnis” (translated by Beare JI, 1931) University of Virginia Library ← chapter
2, G5r (search for ‘river’)
[Interestingly, Aristotle did not describe the reverse motion, rather “…things really
at rest are then seen moving”.]
Mather, Verstraten & Anstis (1998) The motion aftereffect: a modern perspective.
Cambridge, Mass: MIT Press
George Mather’s MAE page (part of his motion site)
Kohn, A, and Movshon, JA (2003) Neuronal adaptation to visual motion in area MT
of the macaque. Neuron 39: 681-691 [PDF]
The Motion Aftereffect homepage
Created: 1997-04-13
Last update: 2013-11-02