What Makes Psychology Different?

From: Stevan Harnad (harnad@cogsci.soton.ac.uk)
Date: Mon Oct 16 1995 - 17:16:15 BST

Thinking Psychologically: 1 (Monday 9 October, 1:40)

Hi Psych Thinkers:

This is a summary of our first seminar.

First a list of who was there:

Nick Bollons
Judy Chatwin
Donna Crumley
Emma Fletcher
Susie Petrie


Alexandra Bilak

(My fault, because I first posted the Wednesday time, which turned out
to be the wrong one...)

We agreed tentatively to meet on Fridays at 11 am (next meeting will be
Friday 20 October) with Monday at 11 am as the alternative time on the
weeks Friday doesn't work.

Before I summarise what we talked about, please remember that you should
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Now in the seminar I asked each of you there why you were studying
psychology. There were various answers, but then I asked what Psychology
was, and a certain amount of uncertainty arose. It emerged that it had
something to do with thinking and the mind, so I asked what kinds of
questions are raised in psychology, what kinds of answers are given, and
what, if anything, makes the kinds of answers given different from those
in other fields, such as mathematics and physics.

Nick suggested that the difference might be that in Psychology you can't
prove that your answers are true, so I asked him what "proof" was. It
turned out that proof is something formal: Something is proved to be
true if it can be shown that if it weren't true, that would lead to a
contradiction. That is (roughly) how proof in mathematics works.

And there is no other field than mathematics in which you can prove
things are true. (Well, philosophers and logicians also have proofs, but
that is a long story -- we might touch on it later.) Other fields,
especially sciences, such as physics, chemistry and biology, don't PROVE
that the answers they give you are true, they just give you a lot of
evidence that makes it very LIKELY that it's true.

So the difference between psychological answers and nonpsychological
answers is not that you can't prove the psychological ones are true,
because because you can't prove truths in any scientific field, nor
in most other fields either.

To show what a transition you make from the world of things that are
provably true (like 1 + 1 = 2, which is true on pain of contradiction)
to the world of things that are true only on the weight of evidence,
I introduced Hume's Problem of Induction: "Induction" is generalising to
the future on the basis of past evidence (compared to "deduction," which
is, basically, mathematical proof).

We are tempted to say that overwhelming evidence is almost as good as
proof, but is it? Is it even any better than just tossing a coin? The
trick is to show why you are better off basing your conclusions on
evidence rather than just tossing a coin. Well, you are tempted to say
that it's because the evidence has worked before: It makes sense for me
to expect that it's going to rain when the pressure and humidity are
high, because in the past, when pressure and humidity were high it
tended to rain much more often than not. So that's why I should pay
attention to past evidence and base my conclusions and predictions on

But if that was supposed to show me that it's best to base my
predictions on past evidence, it doesn't seem to work, because it seems
to depend on my already ASSUMING that it's best to base my predictions
on past evidence. How? Because you tell me: you're best to assume it
will rain when pressure and humidity are high, because of the evidence
that in the past it has tended to rain when pressure and humidity was

But what is on trial here? It is whether it's a good idea to base my
predictions on past evidence. What do you give me as a reason for
thinking it's a good idea? That in the past it has worked! So you
are using induction to justify induction! But if what I'm worried about
is whether it's a good idea to trust past evidence, your telling me that
I shouldn't worry because in the past it has worked isn't exactly
helpful, is it?

Never mind. We can settle for the fact that only proof brings certainty;
and predictions based on the past SEEM to work, so if it ain't broke,
don't fix it: If induction ever starts to fail us, that's the time to
start worrying.

But back to psychology: Another candidate for what makes psychology
different is that people, unlike objects and machines, are
unpredictable. Not only can you not PROVE that they will do or think or
feel this or that, you can't even PREDICT it on the basis of evidence.

Well, the first question is whether this is true only of people (and
animals): The weather is only predictable up to a point; there's
unpredictability there too. And there are some things, like turbulence
and chaos and certain things in quantum physics, that are COMPLETELY
unpredictable, much moreso than we are.

Besides, to a great extent we ARE predictable.

So unpredictability can't be what makes psychological phenomena

But then it became clear that the reason unpredictability was brought up
in the first place was that what -- was it Emma or Donna (I remember who it
was but haven't yet matched the names) -- had in mind was "free will":
You can't predict perfectly what I'm going to do, because, after all,
I'm the one who decides whether or not to do it! And I could always change
my mind if I feel like it.

Mind over matter? The problem with free will is what it's up against.
There is an awful lot of physics -- physics that has worked for an
awfully long time, on an awful lot of evidence, from tiny subatomic
objects to human-size ones like us, all the way to planets and stars in
galaxies light years away from our own -- and all the evidence of
physics has suggested that everything consists of matter and energy,
that energy can take certain forms, and that it is ALWAYS CONSERVED
(neither created nor destroyed, it just changes forms: mechanical to
potential energy when you push a rock up a hill; atomic energy into
heat when you explode a nuclear weapon, etc.).

There have been experiments to see how the mind might fit into this
world of matter: These experiments have been done by
parapsychologists, to show that sometimes you can move things just by
willing it. I described a big upright pinball machine, like a Japanese
Pachinko machine, that spits balls up in the air and then they come down
various paths, usually the middle, sometimes a little to the left,
sometimes a little to the right, to make, on the average, a bell-curve
shape). Human subjects were asked to try to make the machine "skew" the
bell curve leftward or rightward (i.e., make more of the balls go to the
left or the right) using only their minds (not their hands -- the
machine worked automatically; they just sat there concentrating on
influencing the direction balls went).

Sometimes some of them succeeded, with a lot more balls going right
than middle or left. The probability that this would happen was very
low. The trouble was, they couldn't do it consistently. Sometimes it
worked, sometimes it didn't. And even when it worked, it was simply a
very improbable result, something that would happen rarely.

Well, rare things DO happen sometimes. And it was apparent that even if
they did do it with their "wills", they couldn't do it "at will". It
just sometimes happened.

Very few people are willing to put aside the HUGE evidence favoring the
conservation laws of physics because of a few rare events that occur
when medium sized human bodies are in the same room with Pachinko
machines. In the scheme of things, it sounds much more likely that these
are the effects of chance rather than the power of the mind.

Never mind. The free will question doesn't depend on paranormal effects
like mental spoon-bending, we are tempted to reply. It's there even when I
do something perfectly normal, like looking at a pen on my right or my
left, and deciding whether to take one or the other. So supposing you do
that: I put two identical pens in front of you and ask you ("please, if
you are willing, not because I order you to do so, but by your own free
choice") to pick one or the other, whichever you wish to pick.

So you pick the left one. And suppose I try to tell you that you HAD to
pick that one, because of complicated events that started with the "Big
Bang" that started our universe, and continued through the birth of
galaxies and stars, and then the sun and our solar system, the earth,
the oceans, life on earth, the evolution of our species, the advent of
the 20th century, through to the birth of your parents, and of
yourself, and the genes you inherited plus the history you went through
-- all of which conspired to MAKE you pick the left one...

Nonsense, you reply; I picked it because I felt like it; I chose to; I
could have done the opposite just as easily if I wanted.

Fine, you did it because you felt like it: What made you FEEL like it?
Did you CHOOSE to feel like it? Can you really tell me a detailed,
conscious story of what led up to your decision to pick the left pencil
rather than the right one? IS there such a story?

This was almost the end of the seminar; just at the end, the idea of
"reasons" came in: The idea that rocks may move just because of causes,
but people do things for REASONS (or rather, reasons can be causes too,
for people). That sounded like something -- more promising, perhaps,
than unprovability or unpredictability, or even "free will" -- for
setting apart the psychological from the nonpsychological.

We will continue with that next week, but if this summary inspires some
questions or comments, please do send them to me (at the email address:
hsem -- no need to write the rest) and it'll circulate to the rest
of the class, and I'll reply and archive it on the Web as our Skywriting

Remember also to quote the passages you are commenting on, preceding
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Chrs, Stevan

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