[visionlist] [cvnet] Trying to demonstrate stereoscopic vision remotely

Wolfe, Jeremy M.,Ph.D. jwolfe at bwh.harvard.edu
Sat Mar 21 18:42:57 -04 2020

Hi Lester

I think you are leaving out the most straight-forward approach of teaching students how to free fuse

It works quite well with simple stimuli and a little practice.

Here is the relevant figure from our S&P textbook.

Good luck everyone!
[cid:C407D4C8-2FE6-4CE3-821B-69CDCE672280 at fios-router.home]

On Mar 20, 2020, at 10:45 PM, Lester Loschky <loschky at ksu.edu<mailto:loschky at ksu.edu>> wrote:

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Hi Everybody,

If you teach Sensation and Perception, and are currently preparing to teach it remotely, you may have the same question I have: how can you demonstrate stereovision remotely?

As preface, the following are methods I have used in in-person classes to demonstrate stereo vision:

  1.  an actual stereoscope and example stereoimages to share with students (including the classic Julesz square tile random-dot-stereogram image)
  2.  example stereoscopic lenticular lens images to share with students
  3.  red/green anaglyph images with sets of cardboard & plastic red/green anaglyph glasses
  4.  Google Cardboard plus cell phone to share with students
  5.  random dot autosterographic images
  6.  touching two pen tips together using two eyes versus one eye
  7.  learning about crossed vs. uncrossed disparity using two fingers at different distances

Unfortunately, my students don't uniformly have access to the apparatuses required for 1-4 above.

Re. # 3 (red/green anaglyph images), I've thought of having students order a single pair of red/green anaglyph glasses online.  However, it appears that the cardboard and plastic ones can only be purchased in bulk. (I guess they're too cheap to sell individually.)  They also might not arrive in time, but students could still enjoy them once they get them.

Re. #4 (Google Cardboard), I recall getting a free Google Cardboard from the NYTimes several years ago.  However, they are now no cheaper than $5 (Irisu, of India), and likely wouldn't arrive in time.

Regarding option #5 (random-dot autostereograms), I have found that since seeing random dot autostereographic images in depth requires perceptual learning, a large proportion of students don't manage to learn (within the short time period given in a single class period).  (Of course, many students may have a lot of time on their hands now, so they might keep at it long enough to learn to perceive them.  But there will definitely be a good proportion of students who don't try long enough to learn, and so don't get it.)

#6 (touching two pen tips together) is definitely something that can be done remotely.  However, it doesn't have the "Wow!" factor of other demonstrations.  It is more of an "oh, really..." experience to realize how much worse you are with one eye than two.

#7 (using two fingers at different distances to teach crossed vs. uncrossed disparity) can definitely be done remotely.  It is very educational, but again does not have the "Wow" factor.

There is also the finger "hot dog" illusion, which can be done remotely.  It is interesting, but quite different from all of the others in that stereoscopic depth perception is not involved.

For the related phenomenon of motion parallax, "wiggle vision" is a very nice demonstration:

Of course, depth perception from motion parallax is importantly theoretically related to stereoscopic vision (both involve two different images from two different views, one seen over time (and only needing one eye)--motion parallax--and the other seen simultaneously (and requiring two eyes)--stereovision).  But it is not the same as stereoscopic vision, so is a separate but related issue.

For the related phenomenon of binocular disparity, there is the famous "hole in your hand" illusion using a cardboard paper towel roll.  If students have a spare cardboard paper towel roll, they can do this remotely.  But, again, it is a theoretically related but separate issue.

Any other suggestions would be appreciated.

Best wishes,

Lester Loschky
Associate Director, Cognitive and Neurobiological Approaches to Plasticity Center
Department of Psychological Sciences
471 Bluemont Hall
1114 Mid-Campus Dr North
Kansas State University
Manhattan, KS  66506-5302
email: loschky at ksu.edu<mailto:loschky at ksu.edu>
research page: https://www.k-state.edu/psych/research/loschkylester.html
lab page: http://www.k-state.edu/psych/vcl/index.html

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Jeremy M Wolfe, PhD
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