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From: eyal@wisdom.BITNET (Eyal mozes)
Newsgroups: mod.ai
Subject: Re: Representationalist perception
Message-ID: <8607182115.AA00604@ucbvax.Berkeley.EDU>
Date: Fri, 18-Jul-86 18:52:25 EDT
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Posted: Fri Jul 18 18:52:25 1986
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David Sher writes:
>I may be confused by this argument but as far as visual perception is
>concerned we are certainly not aware of the firing rates of our individual
>neurons.  We are not even aware of the true wavelengths of the light that
>hits our eyes.  We have special algorithms built into our visual hardware
>that implements an algorithm that decides based on global phenomena the
>color of the light in the room and automatically adjusts the colors of
>percieved objects to compensate (this is called color constancy).  However
>this mechanism can be fooled.  Given that we don't directly percieve
>the lightwaves hitting our eyes how can we be directly percieving objects
>in the world?

That's exactly the point. We DON'T perceive lightwaves, images or
neuron firing-rates; we directly perceive external objects. The light
waves, our eyes, and the neural mechanisms (which are MECHANISMS, not
algorithms) are not the objects of our perception; they are the MEANS
by which we perceive objects. This will seem implausible only if you
accept the diaphanous model of awareness.

Stephen Barnard writes:
>Consider what happens when we look at a realistic
>painting.  We can, at one level, see it as a painting, or we can see
>it as a scene with no objective existence whatsoever.  How could this
>perception possibly be interpreted as anything but an internal
>representation?

Sorry, I can't follow your argument. Of course, a realistic painting is
a representation; but it is not an INTERNAL representation.  Gibson's
books do contain long discussions of paintings; but he specifically
distinguishes between looking at a painting (in which case you are
perceiving a representation of the object) and directly perceiving the
object itself.

>Gibson emphasized the richness of the visual stimulus,
>arguing that much more information was available from it than was
>generally realized.  But to go from this observation to the conclusion
>that the stimulus is in all cases sufficient for perception is clearly
>not justified.

Gibson did not deny that there are SOME cases (for example, many
situations created in laboratories) in which the stimulus is
impoverished. His point was that these cases are the exception, rather
than the rule. Even if we agree that in those exceptional cases there
is some inference from background knowledge, this doesn't justify
concluding that in the normal cases, where the stimuli do uniquely
specify the external object, inference also goes on.

Since I can't possibly do justice to these issues in a short electronic
message, let me repeat my recommendation of Kelley's book.  It
discusses all these issues in detail, and presents them very clearly.
I'm sure it will be of great value even to those who'll end up
disagreeing with its conclusions.

        Eyal Mozes

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