Transcript Powerpoint Show - Marielle Lange

Cognitive Psychology:
1.
What is Cognitive
Psychology?
Marielle Lange
http://homepages.inf.ed.ac.uk/mlange/teaching/CoP/
General points


I have a French accent + I tend to
speak fast
I will do my best to speak at a decent
rate. If I don’t, do not hesitate to ask
me to speak more slowly.
A copy of the slides will be posted on
the web after each lecture.
http://homepages.inf.ed.ac.uk/mlange/teaching/CoP/

No notes before classes
Course Books
Eysenck, M. W. and Keane, M. T. (1995). Cognitive
Psychology: A Student's Handbook. Hove: LEA. 3rd
Edition. [E&K]
Recommended:
Anderson, J. R. (1995). Cognitive Psychology and its
Implications. New York: W. H. Freeman. 4th Edition.
Sternberg (2003). Cognitive Psychology. Thompson.
for this lecture: E&K, chapter 1
for next lecture: E&K, chapter 5
Course structure
1.
What is Cognitive Psychology?
2.
Attention and Focus 1: focused attention
3.
Attention and Focus 2: split attention
4.
Object recognition 1: recognising patterns
& words
5.
Object recognition 2: recognising auditory
stimuli
6.
Cognitive Representations: Paivo’s dual-
Aims of the course
Demonstrate that cognitive psychology is an
approach, not a specific set of experiments
Show you how different types of evidence are used
to evaluate theories, in cognitive and other
branches of psychology
Illustrate with evidence from four major domains
(attention, vision, language, knowledge
representation)
History
1879
Establishment of first psychology
laboratory (George Wundt, Leipzig,
Germany) – Structuralism
1890
Armchair psychology (e.g., James,
1890)
Problems with the early introspective - methods…
Both structuralism and
functionalism referred to
mentalistic contents of mind
that could not be directly
observed.
Participants (or researchers)
are not always aware of the
procedure they follow to
perform a task (can you tell
me how you do to remember
something?).
© http://lamar.colostate.edu/~bclegg/PY452/PY452_OH1_Intro.ppt
Behaviourist’s reaction
…to stick to the only thing we
can study objectively: the
behaviour that follows an
input.
…and to avoid to introduce
mental variables (or unseen
variables) to explain
behaviour.
© http://lamar.colostate.edu/~bclegg/PY452/PY452_OH1_Intro.ppt
Behaviourist Psychology
1920s
Behaviourist Psychology (derived from learning theory)
“[The behaviourist] dropped from his
scientific vocabulary all subjective
terms such as sensation, perception,
image, desire, purpose, and even
thinking and emotions as they were
subjectively defined.” (Watson, 1930)
Black box metaphor (Skinner?).
Times of change
Von Neuman (1950)

Computer: Representations and processes
(memory, processing system) between input (key
presses) and response (screen display).

Computers:
 Process
information in complex ways
 Store lots of information in memory
 Retrieve information from memory and use it
 Have an input and an output
 Have hardware and software
 Have limited capacity
Information
Processing Theory
(Shannon, 1952)

Mental processes occur in steps or stages.

Each stage has an input and an output.

Each stage transforms the output of the previous stage
in some way.

Each stage has a minimum duration.

Each stage has a limited capacity.

Serial or parallel processing is possible.
Birth of Cognitive
Psychology
1956
Chomsky (preliminary paper on
theory of language)
Miller (“The magic number seven,
plus or minus two”)
Newell and Simon (human problem
solving)
Also Broadbent (1955), human
factors
Cognitive Psychology
Behaviourism (1910s-1950s)
Stimulus
Black box
Response
Cognitivism (from 1950s)
Stimulus
Sensation
Perception
Imagery
Retention
Recall
Problem-solving
Thinking
Response
General framework
Model of human information processing (Wickens, 1992)
© http://lamar.colostate.edu/~bclegg/PY452/PY452_OH1_Intro.ppt
Key concepts
The Cognitive Psychology approach is
concerned with:

the ways in which information is represented in the
mind

and with the processes which act on that information

It does not need not be concerned with the conscious
level (the one accessible to introspection)
It typically uses an information processing
model (expressed as a sequence of processing
stages) to predict the time or accuracy of a
decision.
Information Processing
Analysis Example
http://psych.colorado.edu/~tcurran/psyc2145/lectures/Lec_01_16.pdf
Methods
Empirical
methods
Cognitive
Neuropsychology
Computer
modelling
Cognitive
Neuroscience
Cognitive
Psychology
(modern) cognitive
psychology takes evidence
from all 4 areas to try and
form an understanding of the
human mind
1. Empirical
methods
“Cognitive processes and structures are inferred
from participants’ behaviour (typically speed
and/or accuracy of performance) obtained under
well controlled conditions”
Methodology

Cognitive psychologists have developed techniques for
inferring properties of processing by analyzing
relative response times, error rates, or types of
judgments.

These methodologies are used to test Hypotheses
derived from theories against data.

For example, if there is a discrete module that
compares input to lists stored in short-term memory,
then it should be possible to describe the sequence
of steps or stages through which processing is
accomplished
Sternberg Experiment
Saul Sternberg (1966) proposed a method of
studying how people search short-term memory
(STM) to determine whether certain information
is present.
It is one of the 'classic' examples of the
information processing paradigm in cognitive
psychology.
See http://web.uct.ac.za/depts/psychology/psy300/sternb.html for a
description.
Reference: Sternberg, S. (1969) Memory-scanning: Mental
processes revealed by reaction-time experiments. American
Scientist vol.57, 421-457.
Sternberg Experiment

Sternberg (1966, 1969) developed a
procedure that permits a test of two
questions about the nature of the
search of STM.
(1)
whether the contents of STM are
searched all at once (parallel search)
or one item after another (serial
search).
(2)
whether the search stops when the
item searched for is found (selfterminating search) or whether all
items in STM must be compared to the
item searched for (exhaustive
search).
(In this condition, digits
rather than letters)
Sternberg's (1969)
What do you expect?
 Parallel or serial
search?
 Exhaustive or selfterminating search?
Sternberg's (1969)
findings
What do these data
show?
Parallel or serial
search?
(look at positive set, and how
RT changes with increasing set
size)
Exhaustive or selfterminating?
(contrast positive and negative
sets)
Sternberg's (1969)
findings
38 msec per digit
 Serial search
Similar RT (reaction
times) for positive and
negative answers
 Exhaustive search
Sternberg's (1969) model
Input
Output
7
Yes
397 ms
Perceive
stimulus
Compare to each item held in
memory
=3
?
=4
?
=7
?
Make
decision
38 ms per digit in the memory set
Generate
response
Limitations


Indirect information about the internal
representations and processes.
Artificial set-up, that rarely corresponds to
real-life situations.
2. Cognitive
Neuropsychology
“studies the performance of brain-damaged
patients to infer the mechanisms involved -- in
normal cognitive functioning”
Cognitive
Neuropsychology
Based on a Modularity assumption: distinct
systems which can suffer damage separately from
each other.

Production perfomances
meaning
structure
Patients

Broca


Wernicke


Double
dissociation
Example: Semantic vs syntax: Are the processes
responsible for generating meaning independent of
those responsible for the structure of sentences?
Broca’s aphasia
Difficulty speaking
(telegraphic speech) with
poor syntax (“agrammatical
aphasia”) but semantically
appropriate words.
Son … university …
smart … boy … good
… good …
Wernicke’s aphasia
Speech is
grammatical, but
meaningless
I called my mother on the television
and did not understand the door. It
was not too breakfast but they came
from far to near. My mother is not
too old for me to be young
Limitations


It is difficult to carry out group study (when
patients are group according to a syndrome,
there are variations in performance, in the
group).
The strong locality (or modularity of the brain)
assumption is not well supported by data. It is
not clear that damage to one module “has” only
local effect. It is not clear that areas of the brain
are fully specialized.
3. Computational
models
(mathematical equations, computer
programs, connectionist networks)
Box and Arrows Models
Limits:
 Flowcharts models are never
specific enough.
"What happens in the boxes?”
 “What do the arrows do?”
 “How can the brain be organised
like that?”



Single reaction time model (Newell)
Implementing a theory as a
program is a good method for
checking that it contains no
hidden assumption or vague
terms.
A computer model forces to
clearly specify the format of the
representations and the nature
of the processes.
Production systems as
computer programs
found=0
INPUT digit
:
IF digit = 3 THEN found=1
IF digit = 4 THEN found=1
IF digit = 7 THEN found=1
:
IF found = 0 THEN
PRINT "not found"
ELSE
print "found"
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The mind is a seen as a
symbol manipulation
device.
Note that the speed of
the program is not
directly compared to the
participants’
performance.
Rather, difference in
conditions (Task A takes
longer than Task B, for
both the model and the
participants)
Connectionist networks
1.
all input neurons are connected
to all output neurons
Output Values
2.
Input Signals (External Stimuli)
If units A and B and C
are simultaneously
active, the strength of
the connection
between them will
increase
(and B will be triggered
faster, next time A is
presented)
Connectionist
breakthrough: NETtalk
(Sejnowski & Roseberg, 1986)
Problem of the level of
description
Three levels of description (David Marr)

Computational level : what is computed and why,
abstract description of the set of procesing modules
required to solve the computation (flowchart, schematic
representation).

Algorithmic level : the procedure and representations
used. Theorists attempt to discover the way in which
processing is actually accomplished within each box (cf.
Software program)

Implementational level : the physical instantiation
(the brain, the computer)
What level matters most?
4. Cognitive
Neuroscience
“[Attempts] to establish where in the brain
certain cognitive processes occur, and when
these processes occur… with a tendency to
combine functional and physiological concepts”
Neuroscience
Localisation of brain functions in vivo.
The idea is to look for converging evidence
from different approaches
Summary
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Cognitive psychologists study how information is
represented in the mind, and how those
representations are processed
This approach lets us make and test theories
about the workings of the mind
These processes don't have to be conscious
Neuropsychological evidence may provide insights
into the ways these processes interact
Summary (cntd)
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There are various ways of modelling information
processes; either as a computer program (theory
checking) or as a more brain-like neural net
Different types of models may simply describe the
same processes at different levels of description