What to do – Follow the red dot with your gaze. Observe that some of the squares in the background seem to shift. The effect is fleeting for me – sometimes strong, sometimes missing. But all motion here –apart from the red dot– is illusory.

What else to do & observe – With the popup menu, select “lanes” rather than the circle. Many more settings wait for you to play with them (“Ranomize” is not useful yet).

Comment – This is a variant of the Pinna-Brelstaff illusion which already appeared in their 2000 paper. The same explanation applies.


Pinna B, Brelstaff GJ (2000) A new visual illusion of relative motion. Vision Res 40:2091–2096  [PubMed]

Comments by Ben Backus

More sources on the other Pinna-Brelstaff page.


Created: 2003-Sep-20

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Last update 2018-06-12 by Michael Bach