Demonstrating the twinkle aftereffect
The twinkle aftereffect movie linked to below will have a red dot at the center. To experience the twinkle aftereffect, first position yourself close to the screen, say 50 cm away.
Start the movie and stare at the red dot in the center during the entire time. At the end of the movie, the screen will change to grey. Continue staring at this objectively blank screen and you should then experience faint twinkle where the two grey rectangles were before.
1440x900 version- warning: large (169 Mb) movie file
A clinical use for the twinkle aftereffect
The twinkle aftereffect is a useful tool for exposing defects in the visual field (ref 3 below). When used in such a way, the participant views the twinkling for several seconds as in the previous demo. Subsequently, the entire screen goes grey and the participant may experience twinkling in the areas of the visual field defects. The visual field defects play the role that the grey rectangles did in the previous movie. Here are the twinkle field defect test movies:
1440x900 version- warning: large (171 Mb) movie file
- Anstis 1989
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- Crossland MD, Dakin SC, Bex PJ (2007) Illusory stimuli can be used to identify retinal blind spots. PLoS ONE, 2:e1060.
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- Crossland MD, Bex PJ (2008) The twinkle aftereffect is pre-cortical and is independent of filling-in. Journal of Vision, 8(11):13, 1-10.