If one stares consistently at movement in a particular direction for even a short time, subsequently viewed stationary scenes briefly appear to move in the opposite direction. This phenomenon was known to the Ancient Greeks, but the first modern report of it is often attributed to Robert Addams (1834), who observed the effect while viewing a waterfall at Foyers in Scotland. This demonstration was created from a view of the Falls of Foyers. After gazing at the movie for about 30 seconds (keep your eyes still by fixating on the tree branch in the middle of the falls), pause the movie (click on the pause button in the lower left corner) while maintaining fixation. Do you see an after-effect of movement?
The 'motion after-effect' can be explained by adaptation in visual neurones that respond selectively to moving contours in the image (see Barlow and Hill, 1963). In the absence of image motion, cells tuned to different directions produce roughly equal responses. Exposure to a particular direction of motion alters this balance in favour of cells tuned to the opposite direction, leading to the illusion. A review of modern research on the phenomenon can be found in Mather et al. (1998).
link: http://www.lifesci.sussex.ac.uk/home/George_Mather/Motion/
The 'motion after-effect' can be explained by adaptation in visual neurones that respond selectively to moving contours in the image (see Barlow and Hill, 1963). In the absence of image motion, cells tuned to different directions produce roughly equal responses. Exposure to a particular direction of motion alters this balance in favour of cells tuned to the opposite direction, leading to the illusion. A review of modern research on the phenomenon can be found in Mather et al. (1998).
link: http://www.lifesci.sussex.ac.uk/home/George_Mather/Motion/
