Cognitive ScienceDefinition:“the scientific study either of mind or of intelligence”

Essential Questions What is intelligence? How is it possible to model it computationally?

Takes ideas from Psychology Philosophy Linguistics Neuroscience Artificial Intelligence / Computer Science Maybe also minor contributions from:

Anthropology, Sociology, Emotion studies, Animal Cognition, Evolution

Origins of Cognitive Science Psychology of the early 20th century was dominated by “behaviourism”

Everything should be treated as a behaviour “…purely objective experimental branch of natural science.”

- John B. Watson Goal: prediction and control of behaviour

“Introspection forms no essential part of its methods” - John B. Watson Should not have to describe things in terms of “hypothetical” internals

Such as the “mind”

“Consciousness” not an appropriate question for scientific inquiry This changed around 1950s

Partly as a result of investigations in Artificial Intelligence, partly changing trends

People started talking about Theories of mind Internal representations Computational procedures

Term “Cognitive Science” born in 1973 Came out of AI - Christopher Longuet-Higgins comment on “Lighthill report”

Cognitive Science – Information Processing Cognitive Science views the mind as an information processing system

This is also called the computational view

From this perspective: a human mind’s activity consists of Receive information Store information Retrieve information Transmit information Transform information

Example: a musician improvising Listen to many tunes Remember them Find similarities Come up with rules that say what sounds good together Use those rules in real-time while playing

Understanding Information Processing Systems

1. We attribute non-behavioural properties to the system We say that it has a purpose, goals or desires We say that it has internal beliefs and knowledge and competence We attribute meaning to its external behaviour and internal information We treat other humans like this all the time, call it folk psychology

2. Representation: information in the system can represent real things For example: symbols could represent objects and relationships This would allow a clear separation of what and how

o Alternatively: it could be a messy representation

o what and how tangled together

3. It has procedures for processing information We call these procedures algorithms in computer speak Describes how it does what it does A clear set of steps that need to be followed Like the recipe for making a cake Like the instructions for long multiplication

Three Levels in Information Processing Systems(Marr’s three levels)

What

How

Representation ties together

Physical Implementation

Procedure/Algorithm– clear set of instructions(how to process the inputoutput)

What information is coming in?What information is outputted?What is the relationship?(also explains why it’s important)

Must be physically carried out–Man with paper and pen–Mechanical computer–Modern PC–Human brain (neurons)

Three Levels in Information Processing Systems

What

How

Representation ties together

Physical Implementation

Procedure/Algorithm– clear set of instructions

What information is coming in?What information is outputted?What is the relationship?

Interesting:

Unlike other sciences we can

study top two levels independently from the physical level

Must be physically carried out–Man with paper and pen–Mechanical computer–Modern PC–Human brain (neurons)

Caveat:This is a particular philosophical position, called “Functionalism”.

Some philosophers do not accept it.

Functionalism: mental states (beliefs, desires, being in pain, etc.) are constituted solely by their functional role; i.e. their causal relations to other mental states, sensory inputs, and behavioural outputs.

Consequence: a mind can be implemented in lots of different physical hardware, so long as it performs the right functions.

Three Levels in Information Processing Systems

What

How

Representation ties together

Physical Implementation

Procedure/Algorithm– clear set of instructions

What information is coming in?What information is outputted?What is the relationship?

Interesting:

Unlike other sciences we can

study top two levels independently from the physical level

Must be physically carried out–Man with paper and pen–Mechanical computer–Modern PC–Human brain (neurons)

Caveat:This is a particular philosophical position, called “Functionalism”.

Some philosophers do not accept it.

Functionalism: mental states (beliefs, desires, being in pain, etc.) are constituted solely by their functional role; i.e. their causal relations to other mental states, sensory inputs, and behavioural outputs.

Consequence: a mind can be implemented in lots of different physical hardware, so long as it performs the right functions.

What’s special about a mind then?We know it can do things a computer

can’t do…

A Functionalist claims that the special thing about the mind is the special

information processing tasks, representations and algorithms it uses

One could implement the same functions in a computer – don’t need organic

neurons

Important to Study All Three Levels

What

How

Physical Implementation

Procedure/Algorithm– clear set of instructions

What information is coming in?What information is outputted?What is the relationship?

Could have elegant mathematical theory which no algorithm

can implement

Must be physically carried out–Man with paper and pen–Mechanical computer–Modern PC–Human brain (neurons)

Important to Study All Three Levels

What

How

Physical Implementation

Procedure/Algorithm– clear set of instructions

What information is coming in?What information is outputted?What is the relationship?

But without top level…

Lose sight of what your information

processing is trying to achieve

Must be physically carried out–Man with paper and pen–Mechanical computer–Modern PC–Human brain (neurons)

Important to Study All Three Levels

What

How

Physical Implementation

Procedure/Algorithm– clear set of instructions

What information is coming in?What information is outputted?What is the relationship?

Could have a nice algorithm, but might take too much physical hardware to be

practical

Must be physically carried out–Man with paper and pen–Mechanical computer–Modern PC–Human brain (neurons)

Important to Study All Three Levels

What

How

Physical Implementation

Procedure/Algorithm– clear set of instructions

What information is coming in?What information is outputted?What is the relationship?

Focussing on the physical

interactions here gives you no idea

of what their purpose is

Must be physically carried out–Man with paper and pen–Mechanical computer–Modern PC–Human brain (neurons)

Important to Study All Three Levels

What

How

Physical Implementation

Procedure/Algorithm– clear set of instructions

What information is coming in?What information is outputted?What is the relationship?

Insights from studying the brain could give clues

about the algorithms and representations

which are (or are not) being used

Must be physically carried out–Man with paper and pen–Mechanical computer–Modern PC–Human brain (neurons)

Another Perspective on Cognitive Science Studying different information processing tasks at different levels

Vision Language Memory Problem Solving

Learning

What

(Info Proc Task)

How

(Algorithm)

Physical Implementation

AI and Cognitive Science Two way interaction between AI and Cognitive Science

AI informs Cognitive Science Common to implement a cognitive theory in a computer Run the program and see the ramifications of the theory (Scientific hypothesis testing) Running it may be necessary because theory is complicated

Also, existing AI theories may shed light on the way humans do it

Cognitive Science informs AI Seeking inspiration to solve an AI problem Study the way humans do it Copy in computer …or at least constrain the possible options under consideration

Herbert Simon

““AI can have two purposes. One is to use AI can have two purposes. One is to use the power of computers to augment human the power of computers to augment human

thinking, thinking, just as we use motors to augment human or just as we use motors to augment human or

horse power. horse power. Robotics and expert systems are major Robotics and expert systems are major

branches of that. branches of that. The other is to use a computer's artificial The other is to use a computer's artificial intelligence to understand how humans intelligence to understand how humans

think. In a humanoid way. think. In a humanoid way. If you test your programs not merely by If you test your programs not merely by what they can accomplish, but how they what they can accomplish, but how they accomplish it, then you're really doing accomplish it, then you're really doing

cognitive science; cognitive science; you're using AI to understand the human you're using AI to understand the human

mind.”mind.”

Applications of Cognitive Science Education and Learning

From Cognitive Psychology:

Diagnose and treat children’s reading difficulties

Stroke Therapy

From Linguistics:

Understanding of speech impairments when stroke in left hemisphere of brain

… better therapy

Legal process

From Cognitive Psychology:

Understanding of reliability of memory

Question reliability of legal witnesses

Computing Technology

From AI:

You know loads of examples by now

Cognitive Science – Different Methods Psychology

Controlled laboratory experiments Detailed observations of behaviour

Philosophy Thought experiments Investigate consequences, and coherence of theories

Linguistics Test speakers’ intuitions about “grammatical” sentences Analyse children’s acquisition and errors

Neuroscience Study active brain regions when doing something Study neurons

Artificial Intelligence / Computer Science Write programs, see where they succeed and fail

Cognitive Psychology What are the mental processes in between stimulus and response?

Categorisation

Attention

Memory

Knowledge representation

Numerical cognition

Thinking

Learning

Language

Sight

Hearing

Taste

Smell

Touch

Balance

Heat/cold

…

Voice

Limbs

Fingers

Head

…sensory

input

Motor output

Sensory systems

Central systems

Motor systems

(rough model - Boundaries are not clear in reality)

Cognitive Science – Different MethodsFocus on central unit… Thinking

Draw conclusions from facts, solve problems, plan actions… In many diverse domains

Attention Helps us focus on some task Has limited capacity

Memory (includes Knowledge Representation) Seems to be huge Seems to be no limit on how well it retrieves relevant information

Learning Acquire new knowledge and sensorimotor skills

How does this central unit work?

Physical Symbol System Hypothesis““A physical symbol system has the A physical symbol system has the

necessary and sufficient means of necessary and sufficient means of general intelligent action.”general intelligent action.”

therefore…

human thinking = symbol manipulation

Newell & Simon,1963.

Physical Symbol System Hypothesis““A physical symbol system has the A physical symbol system has the

necessary and sufficient means of necessary and sufficient means of general intelligent action.”general intelligent action.”

Their symbols are taken to mean high level symbols Directly correspond to objects in the world,

such as “monkey” and “table”.

…but the weights and connections in a neural network could also be represented as symbols

Use this to make a “scruffy” representation of “monkey” but that’s not considered to be what they meant

Physical Symbol System Hypothesis““A physical symbol system has the A physical symbol system has the

necessary and sufficient means of necessary and sufficient means of general intelligent action.”general intelligent action.”

Most AI people nowadays would not accept the idea of high level symbols being sufficient

Seems to work well for playing chess, problem solving (if problem well defined)

but doesn’t work so well for some “easy” problems Vision, moving around in the world

But most AI people would accept the computational theory of mind (i.e. Functionalism)

Universal Computing Machine

Turing machine: Actions:

Head can move left and right over the tape Can read and write symbols on the tape

– Can overwrite symbols on tape

Machine has an internal state Takes Action depending on state

Turing’s thesis: “If an algorithm exists then there is an equivalent Turing Machine”

Turing machine is the simplest possible description of a computer that can do anything

All modern computers can be simulated by a Turing machine Only real difference:

Turing machine has infinite tape, real computers have finite memory

Universal Computing Machine How many symbols and

states do you need?

Interesting… If you make some really fancy machine…

Loads of states Loads of possible symbols Multiple tapes Multiple stacks for storing things Many heads working in parallel

You end up with something equivalent to the Turing machine

States Symbols

24 2

10 3

7 4

5 5

2 5

4 6

3 10

2 18

Universal Computing Machine The Turing machine has a set of rules

These determine how it acts

Can make a Universal Turing machine Encode the rules you want it to use on the tape The first thing it does is to read the rules Then follow them… Could also reprogram its rules as it goes along

Important ability for learning Behaviour must change given experience

Universal Computing Machine We said

“If an algorithm exists then there is an equivalent Turing Machine” i.e. a (different) Turing machine is available to do any job we want to do

Now we can say “If an algorithm exists then it can be simulated on a Universal Turing Machine”

i.e. all we need is a single Universal Turing Machine This can do anything

This is the idea behind modern computers Program instructions stored in memory just like any other data Download a program off the web, and start running it You don’t need a different computer for different jobs One computer can do everything

Games, spreadsheet, database, music, movies, photo editor, word processor…

Is the Brain a Universal Computing Machine? Warren McCullogh and Walter Pitts showed

Small collections of neurons can act as “logic gates”(building blocks of computers)

Brain could be viewed as a computing device, just like Turing machine i.e. a brain can do what a computer can do

Other direction is a stronger claim Can a computer do what a brain can do? Can’t be proved But universality of Turing machine suggests… maybe