cognitive science definition: “the scientific study either of mind or of intelligence” ...
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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
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