[spam] Re: Perceptual Illusions (was Re: Ricks theory of uniform correspondence.)

[Martin_Taylor2]

Martin Taylor 2006.08.28.20.56]

[From Rick Marken (2006.08.28.1600)]

So what is a perceptual illusion? The Wikipedia definition of optical illusion (the most familiar kind of perceptual illusion) is as follows: An optical illusion is characterized by visually perceived images that, at least in common sense terms, are deceptive or misleading. Deceptive and misleading relative to what? Since perceptions are the only reality we can know directly, how can they be misleading? Perceptions simply are what they are.

What is a perceptual illusion in the context of the PCT epistemology?

Consider how you would discover that a perception is an illusion. You perceive something else that "ought" to have some relation to the original perception. For example, a line looks curved, but when you lay beside it something like a rule that looks straight, the two both look the same. So, you say to yourself, either the ruler that looks straight isn't straight, or the line that looks curved isn't curved. But it _looks_ curved.

Now you have two different perceptions of the "same" thing. Assuming that there exists an external reality, they can't both be accurate representations of that reality. So, one of them (or both) must be what we call an illusion.

People make fun of Bishop Berkeley for thinking he proved the existence of a rock by kicking it. But he did have a point, in that two very different perceptions that "should" have had a certain correspondence actually did have that correspondence. If his foot had gone straight through where the rock seemed to be, he presumably would have judged the visual rock to have been an illusion.

We say there's an illusion when perceptions that, according to our experience, should have a known relationship don't have that relationship. It proves nothing about "reality", but if the reality exists, then at least one of the perceptions doesn't properly correspond to it. That perception shows an illusion.

Usually, when we talk of an illusory perception, there are more than just two, and they all should correspond, but only one of the group fails to fit with the others. That one has the illusion.

Of course, my ideas are all illusions, too!

Martin

[Bill_Powers1]

[From Bill Powers (2006.08.29.0715 MDT)]

The movers arrive today.

Rick Marken (2006.08.28.1600) –

OK. I think we can all agree
that perception is reality and reality is the current state of our
scientific models.

Why am I not happy with that? Ah, same reason I give for determining what
is an illusion: Things which are equal to the same thing (or each other)
are equal to each other. If perception is reality and the current state
of our scientific models is reality, then perception is the current state
of our scientific models.
In a sense that is right, in that PCT contains a definition of perception
that allows for unconscious perception (presence of a neural signal
in an afferent pathway). However, this leaves out two things: awareness,
and Real Reality.
Bob Clark and I, in the early 1950s, decided that there are three kinds
of reality: Real reality, directly perceived reality, and deduced
reality. The second two can be experienced.
Real Reality is everything that exists.
Directly Perceived Reality is the part of Real Reality that can be
experienced. Experience can’t be denied. If you see a pink elephant in
the corner of the room, there is no way to deny that you see it, the
room, the corner, the label “pink elephant,” and so on. That
experience is happening.
Deduced Reality is a subset of Directly Perceived Reality. It is the set
of all statements (thoughts, etc.) about other parts of directly
perceived reality. “That pink elephant is not real” is a
statement belonging to deduced reality. You can also be aware of the
statement “That pink elephant IS real,” and that, too, would be
part of deduced reality, as would the statement “Those two
statements are contradictory.”
Models belong to deduced reality. In large part, they refer to the parts
of Real Reality that we cannot experience. All we can ever know about
Real Reality, according to our PCT model, is what our sensory endings
present to us in the form of neural signals, which appear to us as
intensities, sensations, configurations, … system concepts. According
the PCT model, these experiences are functions of something that lies
outside our sensory endings in the part of the universe that is partially
described by the models of physics, chemistry, and so forth. We do not
know what functions those are; there is no way we know of yet that
will allow us to discover perceptual transformations that are common to
all input functions in all human beings. Or as I’ve been saying, we
cannot discover any degrees of freedom that are in excess of the number
of degrees of freedom of our perceptual systems. That statement, of
course, is part of deduced reality.

Best.

Bill P.