LINGUIST List 13.2341

Wed Sep 18 2002

Review: Psycholinguistics: Fodor (2001)

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  1. Kornel R. BANGHA, Fodor (2001), The Mind Doesn't Work That Way

Message 1: Fodor (2001), The Mind Doesn't Work That Way

Date: Tue, 17 Sep 2002 15:37:52 +0000
From: Kornel R. BANGHA <kornel.robert.banghaUMontreal.CA>
Subject: Fodor (2001), The Mind Doesn't Work That Way


Fodor, Jerry A. (2001)
The Mind Doesn't Work That Way: The Scope and Limits of Computational
Psychology, Cambridge, Massachusetts, The MIT Press

Book Announcement on Linguist:
http://linguistlist.org/get-book.html?BookID=2753 


Kornel Bangha, University of Montreal

SYNOPSIS

This book is about what could be called the New Synthesis: the
Computational Theory of Mind combined with nativism and
(neo-)Darwinism. It is a response to Pinker (1997) and Plotkin (1997)
who defend the New Synthesis. Fodor's aim is to show that what our
cognitive science has found out about the mind so far is mostly that
we don't know how it works.

Fodor states that CTM is by far the best theory of cognition that
we've got; indeed, the only one we've got that's worth the bother of a
serious discussion. There are facts about the mind that it accounts
for and we would be utterly at a loss to explain without it; and its
central idea - that intentional processes are syntactic operations
defined on mental representations - is strikingly elegant. There is,
in short, every reason to suppose that CTM is part of the truth about
cognition. However, there is no reason to think that this is the whole
story about how the mind works or even a large part of the truth.

In the first chapter, Fodor begins with making a distinction between
Chomsky's story about innateness and the New Synthesis. The author
states that the present phase of nativistic theorising about the
cognitive mind began with two suggestions of Noam Chomsky's: that
there are substantive, universal constraints on the kind of grammars
that natural language can have; and that these constrains express
correspondingly substantive and universal properties of human
psychology (determined, presumably, by the characteristic genetic
endowment of our species). The central problem of language acquisition
arises from the poverty of the ''primary linguistic data'' from which
the child construct a theory of the language; and the proposed
solution of the problem is that much of the knowledge that linguistic
competence depends on is available to the child a priori (i.e., prior
to learning).

Chomsky's rationalism consist primarily in nativism about the
knowledge that cognitive capacities manifest while New Synthesis
rationalism consists primarily in nativism about the computational
mechanisms that exploit such a knowledge for the purposes of
cognition. The New Synthesis shares with traditional rationalism its
emphasis on innate content; but it has added Turing's idea that mental
architecture is computational.

Computation starts, for instance, with the remarkable fact that you
can tell, just by looking at it, that any (declarative) sentence of
the syntactic form P and Q is true if and only if P and Q are
themselves both true: you don't have to know anything about the
nonlinguistic word. This really is remarkable since it's what they
mean, together with fact about the non-linguistic world, that decide
whether P or Q are true. This line of thought is often summarized by
saying that some inferences are ''formally valid'', which is in turn
to say that they hold just in virtue of the ''syntax'' of the
sentences that enter into them. It was Turing's great discovery that
machines can be designed to evaluate any inference that is formally
valid in that sense. The basic thesis of the new psychological
synthesis is that cognitive mental processes are (perhaps
exhaustively) constituted by the kinds of operations that such
machines perform.

Fodor considers that rationalists are nativists practically by
definition. The main idea of rationalist psychology is that beliefs,
desires, thoughts, and the like have logical forms, and that their
logical forms are among the determinants of the roles they play in
mental process. What connects rationalist psychologies and the thesis
that mental processes are computations is primarily the idea that the
logical form of a thought might be reconstructed by the syntax of a
mental representation that expresses it. A rationalist psychology says
that typical laws about the mind specify ways in which the logical
form of a mental state determines its role in mental processes. So a
rationalist is in need of a theory about how a mental process could be
sensitive to the logical form of mental states. Turing's notion of
computation provides exactly what a rationalist cognitive scientist
needs to fill this gap.

In the second chapter, Fodor argues that there are some very deep
problems with viewing cognition as computational, but these problems
emerge primarily in respect of mental processes that aren't
modular. Indeed, Turing's idea that mental processes are computations
(i.e., that they are syntactically driven), together with Chomsky's
idea that poverty of the stimulus arguments set a lower bound to the
information a mind must have innately, are half of the New
Synthesis. The rest is the ''massive modularity'' thesis and the claim
that cognitive architecture is a Darwinian adaptation.

These problems are presented as follows. Mental processes are
sensitive solely to the syntax of mental representations (because
mental processes are computations). Syntactic properties of mental
representations are essential (because the syntactic properties of any
representation are essential). Conclusion: Mental processes are
insensitive to context dependent properties of mental
representation. And this is where the trouble starts. For it would
seem that, as a matter of fact, this conclusion isn't true. Fodor
proposes some counter-examples: simplicity, abductive inference and
conservativism.

Simplicity is the first example of a context-dependent property of
mental representation to which cognitive processes are responsive. The
complexity of a thought is not intrinsic; it depends on the
context. But the syntax of a representation is one of its essential
properties and so doesn't change when the representation is
transported from one context to another. So how could the simplicity
of a thought supervene on its syntax, as CTM requires it?

The author argues that abductive inferences could be computations only
at the price of a ruinous holism; that is, by assuming that the units
of thoughts are much bigger than in fact they could possibly be.

Finally, estimates of which beliefs count for a lot and which ones
count for a little when one is reckoning the conservativism of a
theory change have to be context sensitive. But the syntactic
properties of representations aren't theory sensitive and can't change
with the context.

The third chapter considers some ways in which computational nativists
have tried to evade the limitations mentioned in chapter 2. Fodor
believes that abduction is a terrible problem for cognitive science,
one that is unlikely to be solved by any kind of theory we have heard
of so far. However, cognitive scientists might hope two kids of
solution. Some psychologists think that even if they are unable to
model the global determination of ideally rational inference, they can
produce heuristic approximations good enough to account for the
cognitive capacities that people actually have. Other psychologists
often prefer a connectionist model of cognitive architecture, which
they think has no principled difficulty with holistic effects in
cognition.

The main problem with heuristics is simply that it doesn't work. This
is because reliable abduction may require that the whole background of
epistemic commitments be somehow brought to bear in planning and
belief fixation. But feasible abduction requires, in practice, that no
more than a small subset of even the relevant background beliefs is
actually considered. How to make abductive inferences that are both
reliable and feasible is what they call in AI the frame probleme. The
failure of AI is considered by the author as the failure of the
Classical CTM to perform well in practice.

Fodor argues that there is something fundamentally wrong with
connectionist networks. Since nodes in different networks, or at
different positions at the same network, are ipso facto different
types of nodes, it follows that its position in its network is among a
node's essential features and that nodes can't be ''transported'' from
one network to another. Thus, network architectures haven't any way to
say that representations can have recurrent parts; for example, that
''John loves Mary'' and ''Mary loves John'' do.

Fodor presents in the fourth chapter what modularity is as well as
what his main problem with it is. The author calls the idea that most
or all of cognition is modular the ''massive modularity'' thesis (MM)
and considers that the likelihood of New Synthesis Psychology will
turn out to be a reasonably general theory of the cognitive mind is
hostage to MM. Classical computations are sensitive, at most, to the
local context; and so too are the computations that modular mechanisms
perform. Modular cognition is the kind of processing of which the
Classical computation story is the most likely to be true.

It is sometime claimed that there are very general, adaptationist
considerations that militate in favour of massively modular cognitive
architecture over domain-general architectures, or ''mixed'' ones that
acknowledge computational mechanism of both kinds. According to
Cosmides and Tooby there are three reasons why it's ''impossible in
principle'' that the human mind consist of nothing but domain-general
mechanisms. The first is that definition of error is
domain-dependent. The second is the poverty of stimulus. The third
reason is that combinatorial explosion paralyzes any system that is
truly domain-general.

Fodor examines each of these three arguments and tells us why he
doesn't consider them convincing. At the end of the chapter, he
presents an argument against Massive Modularity: The Input Problem
(i.e. the problem of identifying representations in its proprietary
domain). Really massive modularity is a coherent account of cognitive
architecture only if the input problem for each module can be solved
by inferences that aren't abductive (or otherwise holistic); that is,
by domain-specific mechanisms. There isn't, however, any reason to
think that it can.

The New Synthesis is widely commited to the thesis that ''cognitive
architecture is an evolutionary adaptation'' and one might wonder how
this claim fits with the other two. That's what the last chapter is
about.

Fodor offers a disapproving survey of the main standard arguments for
adaptationism about cognition: consistency, teleology and
complexity. Consistency claims that psychology should be constrained
by the theory of evolution since valid scientific knowledge - whether
from the same or different field - should be mutually
consistent. Teleology argues that functional explication is essential
in the biological sciences and in cognitive science too. The argument
of complexity says that there is no way except evolutionary selection
for Nature to build a complex mind.

At the end of the chapter, Fodor tells us why he thinks there is an
intrinsic connection between adaptationism and the particular kind of
cognitive nativism that New Synthesis psychologists endorse.


CRITICAL EVALUATION

The book is very small (about 100 pages) but the reading is far from
being easy. There is little in it about linguistics and much about
cognitive sciences. Indeed, it concerns several fields: psychology,
logics, Artificial Intelligence, linguistics, and even biology,
philosophy, etc. I would consider it as a merit and a defect at the
same time. It is good to have a large view, and most probably even
necessary for Fodor's topics, but it might be quite hard to follow for
people less familiar with cognitive psychology.

I believe that once you understand the points Fodor writes about, you
get also convinced. Abductive inference remains a problem, not only in
Classical CTM but also in the New Synthesis. This leads us to the
author's conclusion that we don't know much about the mind.

The only point which remains unclear for me in the book is the
following: Why does Fodor think that Plato would have understood
Chomsky well enough, and Turing not at all?


Bibliography

Pinker, S. (1997) How the Mind Works. New York: Norton

Plotkin, H. (1997) Evolution in Mind. London: Alan Lane

Tooby, J. and Cosmides, L. (1992) The Adapted Mind. Oxford: Oxford
University Press

About the reviewer:

Kornel Bangha prepares a Ph. D. of Linguistics and Artificial
Intelligence at the University of Montreal. His research is about how
the process of interpretation of linguistic units in discourse is
influenced by lexical knowledge, by context and by knowledge about the
world.
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