The Hering to Wundt Illusion

Ewald Hering and Wilhelm Wundt were two independent researches who studied similar but opposite illusory effects. The Hering Illusion bends a pair of vertical bars outwards; the Wundt Illusion makes the same bars appear to bend inwards. Use the Slider Bar to move the vertical bars across the illusory backgrounds.

 

New research describes these illusions in terms of the brain's ability to project our world view into the future (The Vision Revolution, 2009).  The burst patterns in the background make the brain think we are moving forward (Hering) or backward (Wundt).  Having decided this, the brain insists that the red bars should begin distorting appropriately as they come forward and sweep by us on either side. The brain thinks we will pass between the red bars as we move ahead, or have passed between them as we move backwards.

 

There is a one 10th of a second delay between the instant we "see" something move and when we perceive that something.  It may not sound like much but it can be critical if you're watching a tennis match or swinging at a pitched ball at more than 90  miles an hour.  To compensate for the built-in delay the brain has learned to project our world view one 10th of a second into the future; this way we always see in the present.  What you are seeing in these illusions is an illusory construct created by the brain; this is what the brain thinks each of the scenes should look like one 10th of a second into your future.

 

Flash: A. A. Azevedo © 2010
Additional Artwork; R. Ausbourne

 

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