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

Russell Hamer russhamer2 at gmail.com
Sat Mar 21 21:11:28 -04 2020

Wonderful image.  Only I am unable to diverge, but I can do all the crossed
stereograms immediately.  Many people I show stereograms to have the same
The hard problem - perhaps harder than finding demos that work well and are
easy to do - is when you try to explain how stereopsis is accomplished in
the brain.  Telling them that there are cells in cortex sensitive to
retinal disparity is not an adequate explanation, even though it is heading
in the right direction.  The correspondence problem is quite difficult for
students to wrap their heads around.  So what's an in-between way of
discussing this for non-specialists that goes beyond saying  "well there
are these special binocular cells that respond to retinal disparity...and
then a miracle happens..."


On Sat, Mar 21, 2020 at 8:20 PM Wolfe, Jeremy M.,Ph.D. <
jwolfe at bwh.harvard.edu> wrote:

> 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!
> On Mar 20, 2020, at 10:45 PM, Lester Loschky <loschky at ksu.edu> wrote:
>         External Email - Use Caution
> 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:
> http://www.well.com/user/jimg/stereo/stereo_gate.html
> https://www.3dwiggle.com/2016/06/28/5-wigglegrams-you-need-to-see-before-you-die/
> 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,
> Les
> --
> Lester Loschky
> Professor
> 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
> 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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