Re: Color constancy

["Promod R. Pratap" <pratapp@UNCG.EDU>]

The process of perception involves a lot more than the chemistry of the retina.
It involves the transmission of the signal from the retina to the brain,
processing at various different stages before the signal gets to the brain,
processing the signal by the brain, and so on.  "Perception" is the sum total
of all these events.  Signal processing involves not only the state of the
signal transduction system (retina, optic nerve, brain, etc) at the instant the
signal is received, but also the history of the system.  Thus, your perception
of color is "colored" (pun intended) by your previous experiences.  A simple
example involves the perception of one field of view when your eye is adapted
to a field of view of a different color. (Actually, this IS a matter of
chemistry -- receptors that respond to the adapting color are bleached, so they
do not respond to that color for some time.)

I think Ludwik Kowalski is correct in his comments below.  Therefore, the
question of whether we perceive the same thing then becomes meaningless.  And
it does not matter if we have different chemistries, as long as we can
distinguish colors.  People who have color blindness cannot distinguish between
colors that others can.

Promod Pratap

> ----------------------------------------------------------------------
>
> Date:    Wed, 1 Nov 2000 16:12:49 -0700
> From:    Larry Smith <Larry.Smith@SNOW.EDU>
> Subject: Re: Color constancy
>
> At 5:41 PM -0500 11/1/00, Ludwik Kowalski wrote:
> > Larry Smith wrote:
> >
> > > But you haven't made a case for it varying from person to person
> > > (assuming they have the same chemicals in their retina).
> > >
> > > Why would you perceive a different color than I do under identical
> > > circumstances?
> >
> > Suppose the chemistry in your retina is dramatically different
> > from the chemistry in my retina, when we are looking at grass.
> > This would not prevent us from using the same word, green,
> > while referring to sensations.
>
> This is certainly true, but 1) is there any evidence that anybody (other
> than color-blind people) has different retinal chemistry than anybody
> else?, and 2) I explicitly assumed that most people have the same
> chemistry; given that assumption why would the perception be different for
> different people?
>
> Larry
>
> ------------------------------


----------------------
Promod R. Pratap
University of North Carolina at Greensboro
Department of Physics and Astronomy
PO Box 26170
Greensboro, NC 27402-6170
Phone: (336)334-3214 (office), (336)334-4279 (lab)
FAX: (336)334-5865