On Fri, 02 May 2008 16:18:51 -0700, Darren New wrote:

> Jim Henderson wrote:
>> Well, the thing is, even when using just one eye, if your brain has had
>> practice at determining how far away stuff is, even with one eye you
>> adjust and still have depth perception.
> 
> Binocular vision really doesn't help much past about 15 or 20 feet.
> After that, it's size and relative velocities.

Yes, I thought I'd remembered hearing that somewhere as well.  But for 
those of us who have "normal" depth perception, just closing one eye 
doesn't reproduce the effect because our brains "fill in the blanks".  
But as you relate down below here, perhaps with a total change in 
environment, that might change the cues enough that the disorientation 
could create that effect.

> I read about this (supposedly true) tribe of natives that lived in the
> Amazon jungles forever. When taken out onto the plains, they thought the
> explorers were magicians, because they could make the cows the size of
> flies. Apparently, they'd never learned how perspective works as they'd
> never been able to see more than 20 feet thru the jungle in a straight
> line. (Couldn't say whether the story was true, but it's supposed to
> be.)

On the one hand, that makes some sense to me, but on the other hand, 
surely they would have recognized that they were moving away from the 
cows....

Jim

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