Minds and Computers : An Introduction to the Philosophy of Artificial Intelligence

is the disposition to (inter alia) engage in food-seeking behaviour,
then I have learned nothing.
The final objection to behaviourism takes the form of an internal
critique: we show that behaviourism fails by its own lights.
Behaviourism is a reductive theory. The whole point of the theory
is to take talk of mental states and replace it, in careful analyses, with
theoretical terms which satisfy positivist criteria of observability and
public verifiability. The aim is to eliminate reference to mental states
entirely by reducing talk of mental states to talk of dispositions to
behave.
Behaviourist paraphrases of mental state terms, however, turn out
to contain ineliminable reference to the mental. To say that Tillie
clutches her jaw is to say more than just that her arm raises in a jaw-
ward direction. To say that she seeks a dentist is to say more than just
that she is impelled dentist-ward. Rather, the attributions of ‘clutch-
ing’ and ‘seeking’ are agentive attributions. To say these things is to
say that Tillie actively, agentively and intentionally clutches, seeks and
so on. This is already a mental attribution.
Human behaviour is always already a mental phenomenon. It is
impossible to enumerate convincing dispositional paraphrases for
mental terms which do not make reference to just such agentive verbs
as ‘clutching’, ‘seeking’, ‘organising’, ‘ensuring’, ‘attending’ and so
on. As such, talk of the mental is ineliminable and the behaviourist
has failed to analyse the ghost out of the machine.
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C H A P T E R 4
NEUROANATOMY
We’re now going to take a brief diversion from our examination of
philosophical theories of mind and develop a rudimentary under-
standing of functional neuroanatomy.
The introduction to neuroanatomy here is going to be very cursory
indeed. My aims in this chapter are quite modest. In the first instance,
I want to show how parts of the brain are specialised for processing
certain functions. In particular, we will see that our linguistic capacity
is strongly localised and subserved by a rather extraordinary neuro-
biological adaptation.
In the second instance, I want to give a basic understanding of the
operations of neurons. This will serve us well much later in the book
when we examine artificial neural networks. Overall, I want to give a
sense of just what an amazing and startlingly complex object the
human brain is.
We’ll begin by describing macro-neuroanatomy – the parts of the
brain which can be seen with the naked eye – and then move on to
describe some basic micro-neuroanatomy.
4.1 MACRO-NEUROANATOMY
The human central nervous system can be broadly divided into three
areas. The spinal cord, the brain stem and the rest of the brain, includ-
ing the cerebral hemispheres which constitute the cerebrum.
The spinal cord (medulla spinalis) is of least interest to us. It carries
signals between the brain proper and the organs and muscles.
Continuous with the top of the spinal cord is the brain stem which
can also be divided into three parts.
The lower brain stem, or hindbrain, contains the pons, the medulla
oblongata and the cerebellum (not to be confused with the cerebrum).
The medulla is known to be implicated in the regulation of heart func-
tion and respiration. The pons (bridge) mostly relays information
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between the cerebral hemispheres and the cerebellum, but is also
implicated in regulating vestibular function (balance).
The human cerebellum (little brain) is highly distinctive. It is very
densely packed with neurons – much more so than the rest of the
brain – and quite regular in organisation for a neural structure of its
size. The cerebellum is readily recognisable by the very fine folding of
its surface, which allows for more surface area and gives it a distinc-
tive wrinkly appearance. The human cerebellum is unique among
mammalian brains in its complexity and intricacy of folding.
The cerebellum is connected to most primary sensory processing
areas and most motor neurons and is known to be implicated in the
automatic governing of fine motor control. When, for instance, you
learn to type without thinking about it, or to operate a motor vehicle
without thinking about it, your cerebellum has been programmed for
the execution of a sequence of fine-grained motor responses to
various sensory inputs.
The next part of the brain stem is the midbrain. The midbrain con-
nects the pons to the upper brain stem. It is known to be implicated
in secondary processing involved with vision and audition. It also
contains the substantia nigra which stimulate production of the neu-
rotransmitter dopamine and which play a role in assisting fine motor
control. Parkinson’s disease, whose su
fferers experience uncontrol-
lable fine tremors, is a degenerative condition of the substantia nigra.
The final part of the brain stem – the upper brain stem – contains
the thalamus and the hypothalamus, as well as the pineal gland and the
pituitary gland. The thalamus, which is continuous with the midbrain,
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