[visionlist] immunity from illusions (particularly visual illusions)

Prof. Michael Bach michael.bach at uni-freiburg.de
Sun Feb 12 11:49:52 -05 2017

Dear Katherine + All:

> …This past semester I had two students who did not experience illusions (out of just 10 students!)
> … and only saw "what was really happening.”
I find that hard to accept, since most “illusions” are a consequence of normal visual processing

> The illusions spanned the course, which is to say they touched upon many different causes. For example, the Hermann grid variations, including the "disappearing dots" one that went viral this summer/fall were affected,
As Klaus says: this would strongly depend on eye movement, that's also the case for the Snakes illusion.

> as well as the color constancy
No aftereffect? How about the Lilac Chaser?

> and size constancy ones like the checkershadow illusion,
Someone who’s not affected by that should have trouble judging material surfaces under realistic lighting conditions

> Ames room
I can believe that. Many Ames models have subtle clues to the oblique interpretation.

How about motion aftereffects? Stepping feet? Wagon-wheel effect? Reverse Spoke Illusion? Sigma Motion? Stroboscopic alternative motion? Angle stuff, e.g. <http://michaelbach.de/ot/ang-arch/> etc. etc.
Can you get them to perceive their blind spot <http://michaelbach.de/ot/cog_blindSpot/>? Do they perceive multistability?

If none of the above is seen – I would have great doubts. Also a good test: fake illusions (e.g. Herman Grids with veridical luminance patches)

Fascinating, thank you! Best, Michael
Prof. Michael Bach PhD, Eye Center, University of Freiburg, Killianstr. 5, 79106 Freiburg, Germany. 
Michael.Bach at uni-freiburg.de   <http://michaelbach.de>

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