Re: [visionlist] immunity from illusions (particularly visual illusions)

Hi, All.  

1) In fact there were many studies of individual differences in visual processing prior to Jeremy’s work, and some of us made them our focus at various times. See here:

Since publishing this short review a year ago, I’ve become aware of many other studies of individual differences that I neglected to include, e.g., studies dealing with stereo and binocular vision. 

2) Regarding individuals who don’t see illusions…  About 5-10 years ago, I met a few people in my S&P courses who reported being blind or relatively blind to illusions, much like what Katherine Moore wrote about.  

I think it would be worth specifying theillusions that individuals like these can and can’t see, and if the deficits are selective or if they truly span many different illusions. There is certainly a range of abilities in the ability to see illusions, with some old research showing a weak general factor that accounts for a range of illusions (e.g. Thurstone, 1944; Roff, 1953, and to a lesser extent, Coren & Porac, 1987).  But I think the most recent research shows that variability in the ability to see illusions is quite selective, with individual differences in the ability to see one type of illusion being a poor predictor of the ability to see other types of illusions. That was a surprise to me. See the recent research by Cappe et al, 2014, and by Grzeczkowski et al. 2017 (in press but available online from Vision Research) (both studies are from Herzog’s lab).  Although Grzeczkowski et al. 2017 don’t discuss illusion blindness per se, they provide a discussion of the research on individual differences in illusions, and they provide a short discussion of Piaget’s (1969) ideas.  Grzeczkowski et al. suggest that there are no common factors for illusions in healthy individuals.  


David Henry Peterzell, Ph.D., Ph.D.–Professor, John F. Kennedy University

On Feb 13, 2017, at 6:42 AM, Simon Rushton wrote:

Piaget looked at suseptibility to illusions in great detail (see his book, Perception, for a summary), he charted in detail, how they changed quite markedly across the developmental span.  Some increase, some decrease.  He categorised the illusions as well, he claimed to be able to explain which increased and which decreased with age.  I was always interested in how his findings fit (or didn’t fit) with the two-visual system story.  Similar questions seem to be prompted if there are significant individual differences.  I never found anyone that thought Piaget’s findings were worth spending any time looking into (note his book is difficult to follow, probably due to the unfamiliar concepts and the translation from French), but maybe his work might shed some light on the individual differences that are being reported here.  His book has a lot of data in it so it might be worth looking for evidence of individual differences within an age group.


On 12 Feb 2017, at 16:53, Qasim Zaidi wrote:

There are individual differences, but they have not been much studied until the recent push by Jeremy Willmer at VSS.

I had a brilliant undergraduate at Columbia, who went on to be a star grad student at MIT, has done start-ups, been CTO of multiple companies, won an Emmy, etc etc, and he had no simultaneous brightness or color induction, as measured by objective methods (nulling on a 2AFC adaptive staircase).  He was also a meticulous observer in motion experiments, where he saw all kinds of effects.

You may want to see what else is different about these students.  I suspect that they will be normal on low level detection and discrimination experiments, but that may still be worth checking.



Qasim Zaidi PhD

SUNY Distinguished Professor

Graduate Center for Vision Research,

State University of New York College of Optometry,

33 West 42nd St, New York, NY  10036.

Office: 212-938-5542; Lab: 212-938-5756; Fax: 212-938-5537


“Dr. Katherine Moore” writes:

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 s 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? 



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


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