Rotating Snakes Illusion


In the Rotating Snakes illusion, subjects see what appears to be spontaneously rotating circular snakes. This type of illusion has been named a “Peripheral Drift” illusion, as the motion only occurs in your peripheral vision. When you focus on a circle, the rotation will cease. There hasn’t been evidence to show that a colored version is more effective than a black and white image. The main building block to allow this illusion to be effective is a sequence of fourĀ  elements of varying luminance; this would be a series of four colors beginning with a black (or darkest color) and ending with white (or the lightest color). Large scale organization is critical as the individual blocks to not evoke a sense of movement.

It is believed that theĀ  four elements of luminance generate local motion signals. Studies have been done that measure the shape of temporal impulse response (TIR) function corresponding to the brightness of the stimuli. With the relative contribution of the transient component falling with decreasing brightness, researchers believe that transient factor of the TIR caused the strength of the illusion.

Retinal ganglion cells carry information to the retina to many different locations within the brain. There are two main categories of these cells, X and Y. X cells have an momentary response initially, but do not show sustained response to stimulus. Y cells respond faster and show more transient responses to the same stimulus. The receptive fields of these cells allow the cells to potentially decipher contrast within the illusion, but not the raw luminance.

Many participants of studies reported that if they focused on the imagine, the illusion failed. This shows that there is a need for the image to be refreshed by blinking or moving the eyes to sustain the illusion.



info from: Understanding the Rotating Snake Illusion by Martin O’Reilly

One response to “Rotating Snakes Illusion”

  1. Aliya Saffran says:

    This is interesting! I used to see this all the time and I’ve always wondered how it works.

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