Transcript Syllabus P140C (68530) Cognitive Science

What is Cognitive Science?
… is the interdisciplinary study of mind and
intelligence, embracing philosophy, psychology,
artificial intelligence, neuroscience, linguistics,
and anthropology
(Stanford Encyclopedia of Philosophy)
http://plato.stanford.edu/entries/cognitive-science/
Practical Value
• Education:
– Intelligent tutoring systems
– Automatically grading exams
• Legal:
– Distinguishing between true and false memories
– Evaluating line-ups
• Sales
– Understanding beliefs and desires
• Information technology:
– Search engines
– Building intelligent systems
Most cognitive scientists are cognitive psychologists, computer
scientists, or cognitive neuroscientists
(from: Schunn et al. 2005)
Understanding
Computation
To understand how
the brain works
Computer Science/
Artificial Intelligence
Interdisciplinary
study of intelligent
behavior
To understand
limits of theories
Cognitive
Science
For human data in
various tasks
Philosophy
To understand
structure of
language
Neuroscience
Linguistics
Experimental
Cognitive Psychology
We will focus mostly on insights from Cognitive Psychology
Areas of Study
• Cognition is about internal processes that are often
unobservable, e.g.:
Perception, Attention, Memory, Visual Imagery,
Language, Concept Learning, Reasoning
?
• Need converging evidence from different perspectives to
really understand cognitive processes
Levels of Analysis
• Implementation:
– Where does mental activity take place in the brain?
– How is processing actually done with neural activity?
• Algorithm:
– What is the abstract representation for input and output?
– What stages are used to process information?
– (Information processing level)
• Computation:
– Why does the algorithm work well?
– What is the goal or purpose of the computation?
(Marr, 1982)
Levels of Analysis Example
Information Processing
• Information processing models resemble processing in
computers – made cognitive psychology popular
• Information made available by the environment is
processed by a series of processing systems
• Processing system is a set of processes that work
together to accomplish a type of task, using and
producing representations as appropriate
• The major goal of research is to specify these processes
and representations
Types of Processing
•
•
•
•
Bottom-up processing
Top-down processing
Parallel processing
Serial processing
An early version of the
information-processing
approach
 purely bottom up or
stimulus-driven
A Demonstration of Top-Down Processing
Top-down processing: perception affected by knowledge of world
Why do we seem to have a fairly robust interpretation of which shapes
are concave and convex when the perceptual information is perfectly
ambiguous? -> perception affected by knowledge
(Kleffner & Ramachandran, ’92)
Top down processing: perception affected by memory
• First time, sine wave speech
sounds incomprehensible
(to most)
http://psiexp.ss.uci.edu/research/teachingP140C/demos/sinewavespeech.aif
• After hearing the natural
utterance, perception of sinewave speech seems to be
quite different
"The steady drip is worse than a drenching rain."
http://psiexp.ss.uci.edu/research/teachingP140C/demos/naturalutterance.aif
(for more info: http://www.haskins.yale.edu/haskins/MISC/SWS/SWS.html)
Sound Induced Illusory Flashes
• Example of parallel and interactive processing:
visual perception affected by auditory perception
• http://www.cns.atr.jp/~kmtn/soundInducedIllusor
yFlash2/
Top-down
processing
Later stages of
processing affect
earlier stages
 can explain effects of
Knowledge, memory,
expectations and context
Parallel vs. Serial Processing
• To illustrate the difficulty of distinguishing
between serial and parallel processing, consider
the Sternberg task
• Goal: what steps are involved in comparing
information to memory? How long do these
steps take?
• Task:
– give subjects memory sets. E.g. 3 9 7
– Probe memory with targets and foil digits: 9 = “yes”,
6=“no”. Measure reaction time.
– Vary the size of these memory sets
Typical Sternberg Results
• Plot reaction time as
function of memory set size
and type of trial
(targets/foils)
• What are the implications of
seeing a linear increase in
reaction time as a function
of memory set?
A serial information processing
model for Sternberg task
9
Perceive
Stimulus
Is it a
3?
Is it a
9?
Is it a
7?
Make
Decision
This serial information processing model predicts a linear increase
yes
A parallel information processing
model for Sternberg task
Is it a
3?
9
Perceive
Stimulus
Is it a
9?
Make
Decision
yes
Is it a
7?
This parallel information processing model also predicts a linear increase
Identifiability
• Identifiability refers to the ability to specify the correct
combination of representations and processes used to
accomplish a task
• Sometimes, behavioral results do not allow processes
and representations to be uniquely identified (e.g.
Sternberg task)
• Need converging evidence to tell theories apart
– More behavioral data
– Data from cognitive neuroscience
– Data from neuropsychology