Organizational Notes
• no study guide
• no review session
• not sufficient to just read book and glance at
lecture material
• midterm/final is considered hard by some
students
• questions will relate to both book and lecture
material
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
Cognitive scientists might have some things to say about
these issues.
Most cognitive scientists are cognitive psychologists, computer
scientists, or cognitive neuroscientists
(from: Schunn et al. 2005)
Understanding Computation
Building computer models that
learn from the environment
To understand how
the brain works
Computer Science/
Artificial Intelligence
Interdisciplinary
study of intelligent
behavior
To understand
limits of theories
Cognitive
Science
Philosophy
Neuroscience
For behavioral data in
various tasks; mental
representations and
processes
Cognitive Psychology
To understand
structure of
language
Linguistics
We will focus mostly on insights from Cognitive Psychology
Areas of Study
• Cognitive psychology/science is about studying 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
• Implementational:
– Where does mental activity take place in the brain?
– How is processing actually done with neural activity?
• Algorithmic:
– What is the abstract representation for input and output?
– What stages are used to process information?
– (also known as information processing level)
• Computational:
– Why does the algorithm work well?
– What is the goal or purpose of the computation?
(Marr, 1982)
Levels of Analysis Example
Cognitive Neuroscience
• the study of the relation between cognitive processes
and brain activities
• Potential to measure some “hidden” processes that are
part of cognitive theories (e.g. memory activation,
attention, “insight”)
• Measuring when and where activity is happening.
Different techniques have different strengths: tradeoff
between spatial and temporal resolution
Information Processing
• Information processing models resemble processing in
computers – made cognitive psychology popular
• Idea is that information is processed in a number of
stages
• The major goal of information processing research is to
– identify those processes
– identify how information is represented
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:
– processing of perceptual information in one modality is
often affected by processing in another modality
• Demo of sound induced illusory flashes:
–
–
–
–
http://shamslab.psych.ucla.edu/demos/
http://www.cns.atr.jp/~kmtn/soundInducedIllusoryFlash/index.html
http://www.cns.atr.jp/~kmtn/soundInducedIllusoryFlash2/
For more information on this effect see:
http://shamslab.psych.ucla.edu/publications/SCR-reprint.pdf
– note: demo might not work on your particular computer
• Demo shows that visual perception affected by
auditory perception
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
• Sometimes, behavioral results do not allow processes
and representations to be uniquely identified (e.g.
Sternberg task)
• Identifiability refers to the ability to specify the correct
combination of representations and processes used to
accomplish a task
How can we tell models/theories apart?
• Need converging evidence to tell theories apart
– More behavioral data
– Data from cognitive neuroscience
– Data from neuropsychology
Note
• Please read book
– to review major brain structures and their functions
– to review brain imaging techniques
• See also additional PowerPoint slides available
on class website
– cogneuro review slides