Can mental content explain behavior?
Introduction
Some representations are mental; others
are not. A road-sign, a map and the utterance of a sentence of a natural
language are non-mental representations. All representations, whether mental or
non-mental, have contents. Some have a conceptual content; others have a
non-conceptual content. For example, motor representations, sensory
experiences, perceptual representations and mental images have non-conceptual
contents. To restrict myself to mental sensory experiences in the visual
modality, visual experiences and visual mental images have pictorial
non-conceptual content. Among an individual's mental representations, thoughts
and propositional attitudes have conceptual contents. And so do an individual's
utterances which, as I just said, are non-mental representations.
No doubt, there are many important
differences between conceptual and non-conceptual content. In this paper,
however, I will disregard the many significant differences between the
varieties of mental contents and I will ask a general question about the
explanatory role of content: can mental content explain an individual's
intentional behavior? Is the content of an individual's mental representation
one of the causally efficacious properties of the individual's representation
in the process whereby it contributes to the production of the individual's
intentional behavior?
Not everything an individual does is
produced by the content of some of the individual's mental representations.
Only an individual's intentional behavior is. The fact that I snore and
vomit - if and when I do - is not something which can be explained by the
contents of some of my mental representations. Nor is it intentional behavior.
Suppose, however, that I move my right hand to the vicinity of a glass
containing water and located a few inches from my chest. Suppose I grasp it,
move it to my lips and drink water from it. What I did when I grasped the glass
and drank water from it is intentional behavior. And it can be explained
by the fact that I believed that the glass in front of me contained water and I
wanted a sip of water. Furthermore, I will assume that my belief that the glass
in front of me contained water is some state of my nervous system. So, I assume
that my brain state has several non-semantic neurophysiological properties. But
it also has content or, as I shall say, it has a semantic property. Now, the
question I want to raise is the following: can the semantic property of my
belief - what I believe - be a causally efficacious property of my brain state?
If many of the neurophysiological properties of my brain state are causally
efficacious in the process whereby I grasp the glass with the fingers of my
right hand, can the semantic property of my brain state be causally efficacious
too?
1. The argument against the causal
efficacy of content
Many philosophers, whom I shall label
intentional irrealists, would respond negatively to this question. On their
view, content cannot be a causally efficacious property of an individual's
mental representation. I think the argument for their view can be put in the
following way:
(1) A decent causal
explanation of why some cause c produced some effet e must refer
to some causally efficacious property of c in the process whereby c
caused e.
(2) Only c's
intrinsic properties (or properties which supervene on c's intrinsic
properties) are causally efficacious in the production of e.
(3) A representation's
content (or meaning) is one of its extrinsic historical properties.
(4) Therefore: the
content of an individual's mental representation R is not causally
efficacious in the process whereby R contributes to the production of
the individual's (intentional) behavior.
Although
I think the premisses are true, I don't accept the conclusion.[1]
So in this paper, I will say why I think the premisses are true and why I think
the conclusion does not follow.[2]
I will assume that in the
non-psychological sciences, it is widely assumed that causal relations hold
between events, as when one says that the short-circuit caused the fire or the
collision between a meteorite and the Earth caused the extinction of dinosaurs.
c caused e. In the psychological domain, we may say that my
belief c caused my bodily motion m. A cause, however, has many
different properties, not all of which may equally be causally efficacious.
Causal efficacy is not fairly distributed among the properties of a cause. In
order to show this last point, I'll borrow a famous example from Fred Dretske (1988).
2. The meaningful sound
Let c be some upper sound
produced by a soprano on a particular occasion, e.g., Tebaldi singing a
particular air of Traviata at a particular time t. Let it also be the
third note of the scale. Suppose c broke a window at t + 1. Call e
the breaking of the window. c caused e. Suppose c had a
meaning. Call it F. Did c cause e in virtue of being F?
Was c's being F causally efficacious in the process whereby c
caused e? No, it wasn't. Why not? Because if c had had another
meaning or if c had had no meaning at all, it might still have produced e;
it might still have broken the window. What was causally efficacious in the
process of window breaking was c's having an acoustic property, K,
not c's being F. If c had not been K, it might not
have broken the window. The reason c's being K was causally
efficacious in breaking the window is that the causal relation between c
and e can be subsumed under a nomic correlation between the fragility of
the window-pane and c's being K. But there is no such correlation
between the fragility of the glass and c's being F.
This example shows, I think, two
things. First of all, it shows that not all the properties of cause c
can be causally efficacious in the process whereby c produces e -
something which is presupposed or implied by the first premiss. Furthermore,
unlike the acoustic property K of the sound, its meaning F is not
one of its intrinsic properties. The acoustic property K is an intrinsic
property of the sound in the sense that the sound would not be the sound it is
if it lacked property K. Arguably, event c which consists
of the producing of a given sound would not be the same event if the sound
lacked its meaning. But there is, I think, a sense in which the sound - unlike
the event of producing the sound - would be same sound if it had the same
acoustic property K and if it lacked semantic property F. But the
sound would not be the same sound if it had semantic property F and
another acoustic property K*. Unlike the sound's acoustic property K,
its meaning F derives from Giuseppe Verdi's intentions. F is
therefore a historical extrinsic property of the sound.[3]
Granted, the sound itself was chosen by Verdi. But its being K, unlike
its being F, did not depend on Verdi's intentions. Verdi gave the sound
its meaning; he did not make up the musical scale.
On my view, there is a difference
between the meaning of a sound produced by a singer and the mental content of a
human being's brain state, e.g., Verdi's musical intention. The latter is primitive
(or original); the former is derivative upon the latter. Generally speaking,
the meanings of non-mental representations are derivative on the meanings of
mental representations. In spite of this difference though, mental content too
is a historical extrinsic property, not an intrinsic property, of an
individual's brain state. It depends on correlations between an individual's
brain on the one hand and properties instantiated in the individual's
environment. This is the substance of the third premiss. To further establish
the plausibility of premisses (2) and (3), I'll now borrow an example from Dan
Dennett (1987). But I'll exploit it in a Dretskean non-Dennettian way.
3. The vending machine
Let S be a French vending
machine emitting soft drinks upon receiving French coins worth 5 French francs.
Call m S's output at t, namely the delivery of a drink via
the opening of a valve in S at t. Call c a particular 5
francs coin inserted in S's slot at t - 1. The insertion of coin c
caused m, the delivery of the drink. Now, c has intrinsic
physical properties P: c is a metal disk with a characteristic
mass, a characteristic physical and chemical composition, a characteristic
diameter, and so on. And c has a monetary value: it's worth 5 French
francs. Call c's monetary value V. What conferred V onto c
is the fact that c stood in some appropriate historical relation to a
person working for the French Treasury Department who imprinted onto it the
requisite "autograph". To see how extrinsic the relation which
conferred V onto C is, let c* be another metal disk which
is physically and chemically indistinguishable from c because it
instantiates P too. If c*, however, did not stand in the required
historical relation to the hands of the right people working for the French
Treasury Department, then in spite of the fact that c* is P,
still c* would lack V. To say that V is a historical
extrinsic property of c is to say that c's being V does
not supervene on c's being P.
No doubt, the insertion of c in S's
slot at t - 1 produced m, the delivery of a drink, at t.
Had some other physical object lacking P been inserted in S's
slot, it would not have produced m. And no doubt c is V.
But the question I want to ask is: was V causally efficacious in the
process whereby the insertion of c caused m? Was the fact that c
was V causally responsible for the opening of a valve in S which
in turn freed a drink? I want to say: No, the fact that c was V
was not causally efficacious in the process of valve opening which in turn
delivered a drink. The vending machine does not really detect monetary value V.
What it is sensitive to are not instantiations of V, but instantiations
of P. The opening of the valve in S is nomically correlated with
property P of c, not with property V. As philosophers say,
property V is "epiphenomenal" in the mechanism by which the
insertion of c produces m.
So, if c's being V
- if the monetary value of a metal disk - is a relevant model of how an
individual's brain state instantiates mental content, then what I believe when
I believe that the glass in front of me contains water does not causally
explain at all what I do when I move my right hand to the vicinity of the
glass, grasp the glass with the fingers of my right hand, move it to my lips
and drink water from it. This in a nutshell is conclusion (4), i.e., the
conclusion drawn by intentional irrealists from premisses (1)-(3). Again, I
accept the premisses. Am I then not forced to accept the conclusion? The rest
of this paper is an attempt to show why not.
4. Why the conclusion does not follow
from the premisses
The vending machine is a physical
device which responds to inputs of a specified kind by producing a
characteristic output: it emits a drink upon receiving metal disks with
intrinsic physical property P and extrinsic property V. The
question we asked was: is c's being V causally efficacious in the
mechanism whereby a valve opens in S and a drink is emitted? Does the
fact that c is V explain m, S's delivery of a
drink? Let's say that this is a question about the mechanism of valve
opening in S. We were, I claim, forced to admit that only property P
of c is causally efficacious in the mechanism of valve opening in S.
Property V of c is not.
Notice, however, that strictly
speaking, the question about the mechanism is not a question about S's
behavior. It is a question about the production of physical motion m.
How can this be? Isn't S's behavior simply m, i.e., the delivery
of a drink? I want to suggest that no, physical motion m - the delivery
of a drink - is not quite the same thing as S's behavior. S's
behavior is a process one constituent of which is m - the delivery of a
drink - and another constituent of which is the cause of m, namely the
insertion of coin c. Indeed, on what I shall call the componential
view of behavior (championed by Dretske 1988 and which I accept)[4],
it is a conceptual mistake to confuse the output of behavior with behavior
itself. As much so as to confuse a constituent of something (e.g., an event)
with what it is a constituent of (a process or a sequence of events). S's
behavior is the process whereby the insertion of coin c in S's
slot at t - 1 produces m, the delivery of a drink at t.
The very fact that m cannot happen at the very instant at which c
is being inserted shows that there are two distinct events: the insertion of c
in S's slot and then the production of m. Thus S's
behavior is a sequence of events which are related to one another as a cause to
its effect. Hence, S's behavior could be symbolized thus:
[c ---> m].
From now on, I will assume that the
componential conception of behavior is on the right track and that S's
behavior is distinct from its output, m, the delivery of a drink. If so,
I can now say why I think conclusion (4) does not follow from premisses (1)-(3).
What reflection on the vending machine example shows is that extrinsic property
V of c is not causally efficacious in producing physical motion m
in S. The economic value of coin c is not causally efficacious in
the emission of a drink via the mechanism of valve opening in S. Nothing
has been said yet about explaining S's behavior. By parity of reasoning,
what follows from premisses (1)-(3) is not that the content of an
individual's representation R is not causally efficacious in explaining
the individual's behavior, which could be symbolized thus [R ---> m]. Rather, what follows
from premisses (1)-(3) is that the content of an individual's representation R
is not causally efficacious in the production of some of the individual's
physical motion, m (where again m is a constituent of the
individual's behavior).
Since I assume that behavior is not
just physical motion, I will now argue that there is a sense in which
explaining S's behavior is not the same thing as explaining the
production of S's physical motion m. What I earlier called the
question about the mechanism was the question: what property of inserted coin c
is causally efficacious in the mechanism of valve opening which yields a drink?
Consider now a different question: why is it that every time a metal disk c
with property P is inserted in S's slot, S does m,
i.e., S emits a drink? Why do instances of the former regularly produce
instances of the latter? This is a question about the structure of S's
behavior in the following obvious sense: what we want to know now is why S's
behavior is a process of a certain type. Why does S's behavior consist
of the insertion of metal disks of type c followed by events of type m,
emissions of a drink? Why does S's behavior consist in the production of
m by c? Why is S's behavior constituted by the
coordination between c and m rather than between c and
something else?
Notice that, unlike the question about
the mechanism, the question about the structure of S's behavior is a historical
question. The question is: how did it come about that insertions of coins of
type c regularly produce events of type m? And the expected
answer to this historical question about the structure of S's behavior
is going to refer to a selective process. Furthermore, I want to suggest
that perhaps c's having extrinsic property V does explain after
all the structure of S's behavior: perhaps, c's being V
explains the coordination between c and m.
Let us suppose first that, thanks to
the efforts of the French Treasury Department, instantiations of property V
are reliably correlated with instantiations of property P. The general
answer to the historical question about the structure of S's behavior
will go like this: c has been coordinated with m because metal
disks of type c with property P were chosen (or selected) by a
human engineer as causes of m, the opening of a valve in S
emitting drinks. The correlation is not perfect: occasionally, the insertion of
a counterfeit - a coin which is not really worth 5 French francs - gets the
machine to deliver a drink. But it is good enough. Presumably, the cost of
designing a more sensitive vending machine is not worth the effort. Notice that
a counterfeit must have intrinsic property P, even though it does not
instantiate extrinsic property V.
Now, suppose that for some reason at
time t, the Head of the French Treasury Department decides to change the
intrinsic properties of coins worth 5 French francs. After t then, there
is no reliable correlation between instantiations of intrinsic property P
and instantiations of extrinsic property V: metal disks with property P
do no more instantiate property V. After t, property V is
to be instantiated by metal disks with intrinsic property P*. If this
were so, then insertion of metal disk c having property P in S's
slot would not cause m any more. After t - assuming that
the price of drinks remains fixed over the change of decision -, French
engineers must design new vending machines such that insertion of metal disks c*
with intrinsic property P* (not P) in their slots will cause m,
the delivery of a drink.
If so, then it's fair to say that some
metal disks with property P* have been selected in the process of
production of m because they instantiate extrinsic property V.
Likewise, before the decision to change the intrinsic properties of coins,
metal disks c having property P were selected as causes of m
because they then instantiated extrinsic property V. Had they not
instantiated property V, they would not have been selected as causes of m
in the first place. So I do want to claim that extrinsic property V does
after all explain the structure of S's behavior. It does explain why
coins with intrinsic property P were selected as causes of m.
Concluding Remarks
To sum up, the vending machine shows
three things. First, it shows that the delivery of a drink, m, is not
the same thing as S's behavior. Second, it shows that we can distinguish
two kinds of causal explanations: the ahistorical explanation of the mechanism
whereby c causes m and the historical explanation of why c
was recruited as a cause of m. Third, it shows that c's being P
is involved in the mechanism whereby c causes m and c's
being V explains why c was recruited as a cause of m. Of
course, coins with property V were selected as causes of m by human
engineers with propositional attitudes (intentions, beliefs and desires). So
the selection process was an intentional process. I have simplemindedly
(I confess) assumed that the causal efficacy of c's being V in
the explanation of the structure of S's behavior is a relevant model of
the causal efficacy of mental content in the explanation of an individual's
intentional behavior. It is incumbent upon anybody who makes such an assumption
to show two things. The first is to argue that the content of an individual's
mental representation R can indeed explain the recruitment of R
as a cause of some physical motion m of some of the individual's bodily
parts. The second is to argue that the selection process whereby R was
selected as a cause of m is a non-intentional process.
I will merely ask you to imagine a prey
which I'll call D (for deer) executing some flight motion m at t.
I grant that the prey's behavior is not voluntary behavior because it is
instinctive. However, I will assume that it is intentional because the flight
motion is caused by some internal representation. I will now argue that we can
at least ask three different questions about D's flight motion m.
First, we can ask: why does D
produce m at t? Answer: because at t - 1, D
detected predator P in the vicinity. Call c D's internal
state whereby D dectected its predator. The presence of predator P
prompted D to enter c at t - 1 which in turn caused m
at t.
Secondly, we can ask the ahistorical
question: what is the internal mechanism whereby c in D causes m?
General answer: motor neurons in D's motor cortex are wired to fire upon
receiving inputs from sensory neurons in D's visual (or olfactory)
system. And the former in turn govern muscle contraction in D's limbs.
Presumably, the fact that c represents or reliably indicates the
presence of predator P is not part of the answer to the question of the
mechanism whereby why c causes m.
Finally, consider the historical
question: how did it come about that every time D is in state c, D
does m? Why does it do m rather than something else? Why was c
recruited as a cause of m, flight movement, rather than fight
movement m' or no movement at all? The answer, I think, to this
last question, would come in two steps. First, c was recruited as a
cause of m (flight movement) in D by natural selection. I assume
that natural selection is a non-intentional selection process. In the
competition for survival between ancestors of preys of type D and other
animals which were preys of ancestors of predator P, natural selection
favored the former because they had a coordination between c and m.
Preys of ancestors of P which lacked a coordination between c and
m did not survive and went extinct. Secondly, natural selection would not
have recruited c as a cause of m in ancestors of D if c
had not been correlated with the presence of predator P. In other
words, I claim, c would not have been turned into a cause of m by
natural selection if it had not been a reliable indicator of the
presence of a predator.
Like property V of coins, the content
of a prey's perceptual state c - its being a reliable indicator of
predators - is a historical extrinsic property . It too, I suggest, plays a
causal role in the historical explanation of the structure of the prey's
behavior: it contributes to explaining why c was coordinated with flight
motions m in the presence of predator P. Unlike the monetary
value of coins, however, the content of the prey's brain state turns on natural
selection, which is a non-intentional selection process.
References
Churchland,
Paul M. (1984) Matter and Consciousness, Cambridge, Mass., MIT Press.
Davidson,
Donald (1980) Essays on Actions and Events, Oxford: Clarendon Press.
Dennett, Daniel C.
(1987) "Evolution, Error, and Intentionality." In Dennett, Daniel C.
(1987) The Intentional Stance, Cambridge, Mass., MIT Press.
Dretske,
Fred (1988) Explaining Behavior, Cambridge, Mass., MIT Press.
Fodor, Jerry A. (1987)
Psychosemantics, Cambridge, Mass.: MIT Press.
Jacob, Pierre (1997) What
minds can do, Cambridge: Cambridge University Press.
Putnam, H. (1974)
"The Meaning of 'Meaning'", in Putnam, H. (1975) Philosophical
Paper, II, Cambridge: Cambridge University Press.
Quine,
Willard Van Orman (1960) Word and Object, Cambridge, Mass.: MIT Press.
Stich, Steve (1983) From Folk Psychology to Cognitive Science, Cambridge, Mass.: MIT Press.
[1]Unlike many philosophers, I think content can explain some of the things an individual does. It is an open question whether Davidson's (1980) anomalous monism allows content to explain intentional behavior. Eliminative materialists such as Quine (1960), Churchland (1984) and Stich (1983) explicitly deny it. So does Dennett (1987) according to whom there cannot be semantic engines. And so does Fodor (1987) who thinks that syntactic, not semantic, properties of mental symbols can be causally efficacious.
[2]This argument makes use of the contrast between a thing x's intrinsic and extrinsic properties. Although the contrast is notoriously hard to capture, it is, I believe, useful. Intuitively, a property is intrinsic just in case its being instantiated by x at time t does not depend on anything other than x at t. It is extrinsic if it is not intrinsic.
[3] The extrinsicness of meaning has been emphasized notably by Putnam (1974).
[4] See Jacob (1997, ch. 8).