In this illusion named “
Dialogue du vent et de la mer” by
Prof. Akiyoshi Kitaoka, the image appears to wave while there is actually no moving component. The illusion is due to eye-movements and the local spatial contrast present in each element: the asymmetrical placement of the dark and bright edges around each blue element creates a local spatial luminance gradient that is replicated over space. With small eye-movements, this local spatial gradient is perceived as a local motion that spreads over space according to the distribution of the spatial gradient direction, hence the wavy nature of the perceived motion flow.
How do the properties of the local element affect the perception of this illusion? This widget allows you to play with some important parameters that directly affect the appearance of this illusion, for example:
- Contrast: the strength of the effect is directly correlated with the contrast between the dark and bright edges around the blue element;
- Gradient distribution: a smooth distribution enhances the illusion through spatial propagation while a local opponent distribution breaks it;
- Color: some color combinations provide a stronger sense of motion.
Note that if you stare carefully at the image without making any eye-movement, the motion illusion may disappear ! Let your eyes wander and the illusion comes back ! Be careful, this illusion may induce nausea or some visual discomfort...
This illusion was originally created by Prof.
Akiyoshi Kitaoka from Ritsumeikan University (Kyoto, Japan). Several other variations as well as some additional explanation can be found on his website:
http://www.psy.ritsumei.ac.jp/~akitaoka/wave-expe.html
Prof. Kitaoka specialized in visual perception and visual illusions of geometrical shape, brightness, color, in motion illusions and other visual phenomena like Gestalt completion and perceptual transparency, based on a modern conception of Gestalt Psychology. He became renowned through his Rotating snakes illusion. To learn more about all the illusions he created over the years, check out his website:
http://www.ritsumei.ac.jp/~akitaoka/index-e.html