Theoretical Issues in Psychology
Philosophy of Science
and
Philosophy of Mind
for
Psychologists
B&LdJ
1
Chapter 8
Modern approaches to mind (2)
• Neural networks and connectionism
• ‘Classical’ versus connectionist architecture
• The third contender: dynamicism
• Is there need for ‘mental representations’?
• Naturalism, reductionism and folk psychology
B&LdJ
2
Neurophilosophy (the Churchlands)
Contrary to Fodor’s ideas:
• For answers to philosophical-psychological questions
turn to the neurosciences (empirical knowledge naturalism).
• No autonomy for psychology.
• Brain-based view of mind: ‘mind is brain’ (but no mindbrain identity).
• Eliminate folk-psychological concepts.
• Against sentential (propositional) LOT-view of knowledge.
• No solipsism, but evolutionary adaptation.
B&LdJ
3
Model of a neural network
• Set of nodes and connections between them.
• Activation spreads through the network.
• Giving weights to the nodes.
• Three layers: input, output, midden layer of hidden nodes.
• Network learns by adjustments of weights.
• According to some learning rule (‘Hebb rule’).
• Does the training by itself, is tuned to the environment (is
not pre-programmed).
• Maintains fault tolerance, graceful degradation (functional
persistence), and satisfies soft constraints (all unlike
programs).
• Knowledge/representations is/are distributed over many
connections.
• Network is model of human mind: ‘connectionism’.
B&LdJ
4
Working of a (quasi-neural) network
(here, a network of a submarine, learning sonar signals)
B&LdJ
5
Activation space and prototypes
• Learning to recognize is forming a prototype, a
hotspot in a vector or activation space.
• A concept is a prototype (not a symbol string).
B&LdJ
6
Connectionism
• (Quasi-)neural networks:
• ‘neural’ patterns of activation (versus symbols and
inborn rules);
• online selforganisation (versus offline programs);
• support cognitive tasks.
• Basic cognitive processes (formation of representations)
are patterns of activation (not manipulation of symbols).
• Cognition is basically pattern recognition.
• Neurophysiology, c.q. neural networks, explains
cognition: ‘cognitive neuroscience’, cognitive theories
which are neurological plausible and naturalized:
• no functionalism;
• no autonomy for psychology.
B&LdJ
7
Representational capacity of human brain
• Human brain has: 100 billion neurons =
100.000.000.000 (1010).
• Every neuron has: synaptic connections with
10.000 (104) other neurons.
• In a human brain: 1014 synaptic connections.
• Weight of each connection can have a value of 1 out of 10.
• Thus human brain can contain:
101014 = 10100.000.000.000.000
cognitive configurations
(cfr. total elementary particles in universe estimated 1087).
B&LdJ
8
Symbolic versus connectionistic systems
Fodor: thinking is characterized by productivity, systematicity,
i.e. a continuous recombination of discrete symbols:
compositionality, like building sentences with words: requires
formal structure (networks lack structure and are not strong
enough to simulate cognition; leaves you with nothing more
than a plain associationpsychology);
so, LOT is ‘the only game in town’: thinking occurs in a formal
language; the only explanation of structure.
Connectionists (a.o. Smolensky): thinking is network
activation, compositionality is a by-product of networks:
‘functional compositionality’: doesn’t need a symbolic
architecture; productivity of language is not the only possible
productivity (Churchland).
B&LdJ
9
Third Contender: Dynamism: ‘mobots’ and
dynamic systems
• Dynamic coupling of organism and environment.
• Activity in environment (no inner representational
domain).
• Online interaction (no innate structure and programs).
• Evolution and time (no static representations).
• Adaptation.
• Dynamic system (no representational structure: LOT or
patterns of activation).
• Cognition is like playing tennis, rather than chess.
B&LdJ
10
Dynamism: mobots
Mobots : internal representations
and computations redundant.
Rodney Brooks: robot with
response systems, direct
interaction with environment,
without central representations.
B&LdJ
11
Dynamism: Watt governor
Cognition is on-line real-time interaction with the
environment – Watt governor, continuous following and
control of behavior and environment; reciprocal
causality.
B&LdJ
12
Mental representations redundant?
The absent and the abstract:
• there are ‘representation-hungry’ situations.
• that require higher cognitive functions like abstract
thinking, imagination and reflection.
• Direct coupling mainly in sensori-motor functions.
• External symbols for higher cognitive tasks (planning,
abstraction).
• ‘Active externalism’ (extended mind, Ch 9.4): for some
cognitive tasks we use external instruments, e.g., paper and
pencil, graphical devices; books, internet.
• ‘Leaky cognition’: brain and environment cannot be
separated.
Andy Clark (1997, 2003)
B&LdJ
13
Naturalism and neurophilosophy Churchland
Naturalism: representation is biological phenomenon, product
of evolution.
Cognition is pattern recognition, not symbol manipulation.
Language appears late in evolution, therefore no LOT.
Functionalism is a conservative ‘cheap# explanation.
Folk psychology (beliefs and desires) stagnating program,
isolated from scientific progress.
Folk psychology eliminated and replaced by neuro-speak.
B&LdJ
14
Churchland: Naturalism and neurophilosophy
Naturalistic (neuroscientific) explanations of:
• knowledge as coded in connection weights;
• representation and intentionality as processes in the brain;
• sense of self;
• morality as cognitive skill; role of oxytocine in building trust
and love.
B&LdJ
15
Eliminativism and folk psychology
Folk psychology (‘belief-desire’) is a kind of theory, explains
behavior (Fodor + Churchland).
Fodor: in principle correct theory:
• beliefs and desires exist really as symbol structures in LOT;
• are causes of behavior;
• folk ps. vindicated by CTM;
• intentional laws, generalisations, and predictions
indispensable: folk psychology is successful predictor;
•intentional realism.
B&LdJ
16
Eliminativism and folk psychology
• Churchland: folk psychology obsolete theory:
• stagnating program (Lakatos);
• no progress, no connections with current development in
science;
• replace by neuroscience;
• eliminativism.
• Clark, Dennett: folk psychology is not a scientific theory,
• beliefs and desires only descriptive (‘intentional stance’),
not internal causes (‘design stance’), not literally true;
• different explanatory aims; different level from
neuroscientific explanation;
• instrumentalism.
B&LdJ
17
CTM
Connectionism
Formal, syntactical rules, Weights and activation
symbols
patterns
Preprogrammed, no real
development
Self-organisation,
learning through
adapting weights
Brittle program rules
Graceful degradation
under damage
Structured, language-like ‘Associationism’
architecture,
concatenating discrete
symbols
Productivity and
Functional
systematicity through
compositionality
compositional
architecture
Functionalism, autonomy Reductionist, (more or
for psychology
less) brain-like cognition
Representations are
symbolic structures
Solipsism, self-contained
mind
Representations are
activation patterns
Representations are
products of interaction
with environment
B&LdJ
Dynamic systems
Coupled co-evolving
systems, developing over
time
Evolving through state
space, circular causality,
continuous adaptation
Smooth mutual
adaptation
Development in time
Trajectory through state
space
Emergent properties of
organism-environment
system, and
development
No representations
needed
Body mind and world
part of a single system
18