Re: an optical illusion?

[Maurice Barnhill <mvb@UDEL.EDU>]

Rick Tarara wrote:
> ...
>  The question still remains why
> the brain would trigger one eye to preferentially view the blue and the
> other the red (I'm assuming this is the case since covering one eye makes
> the illusion disappear.)
> ...
> Rick
The brain will do just about anything to improve perception.  I have
eyes with very different amounts of nearsightedness.  One naturally
focusses nearby and gives very blurred vision at a distance, and the
other normally focusses at a distance and is quite unable to see
anything nearby very clearly.  My brain uses the information from one
for things nearby and the other for things far away, giving me clear
vision for all distances.  I didn't even know about this until I got old
enough that the clear regions from my two eyes no longer overlapped and
I started having trouble playing racketball for lack of 3D perception in
middle distances.

If the difference between the best-focus points of red and blue is large
enough, I would not be surprised if the brain somehow arranges to get
sharply focussed red in one eye and sharply focussed blue in the other,
and combines the two images selectively to get an overall sharp image.
In that case you *would* need both eyes to see the distance illusion.
--
Maurice Barnhill (mvb@udel.edu)
Department of Physics and Astronomy
University of Delaware
Newark, DE 19716