Re: [photo-3d] seeing 3-D: innate

[John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>From: "John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>
>Subject: Re: [photo-3d] seeing 3-D:  innate

>This was a very fascinating test, that I have often wondered about.  The
>problem is, how do you completely eliminate all monocular depth cues?  The
>cube and box would have to be designed very carefully, such that from the
>observer's distance and perspective the squares of the checkerboard pattern
>appeared identical in size and shape at the different distances (they would
>appear perfectly square only on-axis; from all other positions they would
>appear to be trapezoids).  And lighting.  Any shadows, texture, reflections,
>etc. would be very revealing.

>The most difficult monocular depth cue to try to eliminate would be that of
>relative motion.  It is very difficult for most people to hold their head
>perfectly still.  The slightest motion of the head would instantly reveal
>depth differences...


>Anyway, does anyone know how the researchers performing the checkerboard
>pattern experiment prevented their human or animal subjects from perceiving
>distances through relative motion?  Most animals and babies don't hold their
>head perfectly still for very long.

>JR

I have seen films of at least one test of this type (probably in psychology
class in high school), and my recollection is that there were no controls
of that type. (Or perhaps the film makers thought scenes of babies with their
heads clamped in place or wearing eye patches would be too disturbing for
high school students to watch).

My impression was that the study was to determine whether babies have
perception of a vertical drop and seek to avoid it, not the specifics of
how they perceive the drop. (I think at the time it was claimed that humans
have only two instinctive fears - falling and loud noises - and all other
fears are learned.)

If this recollection is correct, then the experiments would not be a valid
test of whether babies have stereoscopic depth perception.

John Roberts