[visionlist] observer rejection query

[martybanks at berkeley.edu]

We find that a lot of inexperienced observers can't initially see depth in
random-element stereograms. They see them as flat. Not sure what
percentage, but I wouldn't be surprised if it's 25%. With practice, the
great majority learn to see depth just fine.

Nearly all inexperienced observers can see depth in stereo photographs
where other depth cues are consistent.

Regards,

Marty

>
> A query to all psychophysicists, and especially to those working in
> binocular
> vision.
>
> We are working on a study using a large number of totally naive observers
> (dozens of people rather than 3-4).  We're finding that many cannot
> achieve
> threshold in a binocular vision task, sometimes around 25% of people.
>
> That sounds like a lot, until you start sampling the psychophysics
> literature,
> where binocular vision (and other) studies often report that 'observer X
> was
> rejected because they could not do the task'.  With just a handful of
> observers, losing 1 _could_ really reflect 25%.  Question is: HOW MANY
> people
> typically can't do these tasks?  I'd like to work out a reasonable
> expectation
> for the proportion of observers who deliver unusable data (whether
> reported in
> publications or not).
>
> I'd be very pleased if you could let me know your own experiences from
> your lab
> studies (or others you may know of).
>
> I will summarise any responses and post on visionlist.
>
> regards
>
> Julie Harris
>
> **********************************
>
>
> Julie M. Harris
> Professor of Psychology
> School of Psychology
> University of St. Andrews
> St. Mary's College
> South Street
> St. Andrews
> KY16 9JP
>
> Julie.Harris at st-andrews.ac.uk
>
>
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