[visionlist] immunity from illusions (particularly visual illusions)

[Liu, Lei]

Maybe you want to test your students’ vision first, acuity, contrast sensitivity, color vision and so on. Some illusions may not survive impaired acuity or contrast sensitivity. I happen to have a Bangerter Foil Bar handy that generates different degrees of visual blur. I used it to test some online samples of visual illusions you mentioned. I failed to see the dots in the Hermann grid through some of the foils, in the original grid as well as the new ones in Perez, Archer & Artal’s 2010 paper (IOVS, 51:609-613). When viewed through a stronger Bangerter foil, areas A and B of the checker shadow demo do appear to have similar colors (B appeared to blend in with its darker neighbors). These are just my casual observations. There may have been controlled studies on the dependence of visual illusions on normal vision.
Best
Lei Liu
School of Optometry
University of Alabama at Birmingham

From: visionlist [mailto:visionlist-bounces at visionscience.com] On Behalf Of Dr. Katherine Moore
Sent: Saturday, February 11, 2017 9:08 PM
To: visionlist at visionscience.com
Subject: [visionlist] immunity from illusions (particularly visual illusions)

Dear vision experts,

I was hoping some of you could help me out with something that made me curious all of last semester. Last semester was about the fifth time I've taught Sensation & Perception. Even though my classes are small (less than 25 students), each time I teach this course I have a student or two who is unusual in some sensory way -- just one working eye, synesthesia, no sense of smell, blind, prosopagnosia, etc.

This past semester I had two students who did not experience illusions (out of just 10 students!) One of them truly did not experience any of the illusions. Another did not experience the vast majority of them. We mostly did visual illusions, but among the few auditory illusions we did, these students didn't experience them either. I have no reason to think the students were lying about it--they are very sincere people. And they both had trouble with an assignment that required students to view some new illusions, describe what they saw and what was really happening, and explain the illusion. These two students didn't see what the rest of the class saw, and only saw "what was really happening."

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 well as the color constancy and size constancy ones like the checkershadow illusion, Ames room, etc.

What do you all know about this, like what the cause could be for this immunity from illusions of many kinds, or individual variation in the experience of illusions?

Best,
Katherine

Katherine S Moore
Assistant Professor of Psychology
Arcadia University
450 S. Easton Rd
Glenside, PA 19038
Office: Boyer Hall room 128
Phone: (215) 517-2429
https://sites.google.com/a/arcadia.edu/amclab/
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