Re: weighting depth clues

[T3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>From: T3D Jim Crowell wrote:

>At 6:53 AM -0700 7/21/97, T3D Richard Young wrote:

>>I recently asked my colleague Gerald Westheimer at Berkeley "Why 3D?"
>>Here is his reply:
>>>There was an article the other day in the newspaper about a pilot who had an
>>>accident...

>...I find it very hard to believe that stereo is important for
>flying...except maybe in the cockpit, perhaps the guy reached for the
>throttle & missed?

I certainly make use of stereoscopic vision while driving. I believe takeoff
and landing are the most critical moments of a typical flight, at which time
objects on the ground are close enough for stereoscopic vision to be operative.

Incidentally, isn't it the movie "Flying Tigers" (set sometime around the
beginning of WWII), in which a pilot flunks his depth perception test,
flies anyway, and (naturally) crashes?  Granted that it's a fictional movie,
it may indicate that there was some interest at that time in depth perception
of pilots.

>>>   incidentally, about 98% of college biology students have acceptable
>>>stereopsis and 3-D is an exceedingly good tool for demonstrating molecular
>>>structure.  More people have full stereoptic capability than full color
>>>vision!

>That's interesting.  I wonder if that means there's actually a difference
>between college students & others or if it's a criterion effect?  i.e.
>there are probably degrees of stereoblindness, maybe the 7% figure was
>arrived at by placing the dividing line at a different point...

Also, the college students may understand the instructions for taking the
stereo vision tests better than the average population.

Regarding the comment in the previous post that 7% stereoblindness might
indicate low evolutionary pressure for stereo vision, I'm somewhat skeptical
too. As I understand it, stereoblindness is somewhat of a "fallback position"
as an alternative to functional blindness. I agree that the human visual
system places a far higher priority on achieving some form of vision than
on perfect stereo vision. The idea of evolutionary pressure (as an explanation
for a particular physical or behavioral feature of a modern organism) is
still considered somewhat controversial in some quarters, but perhaps it
could be argued that since humans and their predecessors have apparently been 
living in communities for millions of years, what mattered was that the
majority of those present have good stereo vision, so they could
hunt/fight/etc. for the benefit of the tribe.

Nowadays, cars and stairs continue to provide some evolutionary pressure to
favor development of stereo vision. :-)

John R


------------------------------