Afterimages
Jennifer Alexander
What is an afterimage?
An afterimage is an image that is perceived after the original source of stimulation is removed. A visual afterimage usually occurs after one views a high-contrast stimulus for 30-60 seconds. Playing with afterimages doesn’t hurt the brain!
Types of afterimages:
- motion after-effect
Color After-Effects
:Every color has an opposing color. (Yellow/Blue) (Red/Green) (Black/White) For example if you look at a yellow stimuli for 30-60 seconds and then look away you will see a blue after image.
Stare at the center of this flag for 30-60 seconds and then look away at a white surface. What do you see? You should see a red, white, and blue flag.
You can find this flag on the internet at: http://www.tc.umn.edu/~scott/flash/flag.html
Motion After-Effects:
This occurs when you stare at something that is moving in a particular direction for at least 30-60 seconds. When you look away from the movement and look at a stationary scene it will appear to move in the opposite direction.
Examples:
-waterfall illusion
if you look at a waterfall for about one minute and then look away at the stationary image that you see will appear to be moving in the opposite direction
http://www.biols.susx.ac.uk/home/George_Mather/Motion/MAE.HTML
- spiral motion aftereffect
when you stare at a spiral that appears to be moving inward and then look away at a stationary image it will briefly appear to be expanding out and moving in the opposite direction.
http://dogfeathers.com/java/spirals.html
Tilt After-Effects:
This occurs when you stare at these high contrast lines that are slightly tilted and then look at a different tilt.
Example: Stare inside the circle which is in the center of the middle square. After viewing this for about 30-60 seconds then look at the center of the square on the left. The lines should appear to be slightly tilted to the right even though they are vertical. When you try the right square you will not see a tilt after-effect because the orientation of the lines is too different from the lines in center square.
