cognitive psychology: marielle lange 1. what is cognitive psychology?
TRANSCRIPT
Cognitive Psychology:Cognitive Psychology:
Marielle LangeMarielle Langehttp://homepages.inf.ed.ac.uk/mlange/teaching/CoP/http://homepages.inf.ed.ac.uk/mlange/teaching/CoP/
1.1.What is Cognitive What is Cognitive
Psychology? Psychology?
General pointsGeneral points
I have a French accent + I tend to speak fastI 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 BooksCourse 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 structureCourse 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-route hypothesis
Aims of the courseAims 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)
HistoryHistory
1879
Establishment of first psychology laboratory (George Wundt, Leipzig, Germany) – Structuralism
1890
Armchair psychology (e.g., James, 1890)
© http://lamar.colostate.edu/~bclegg/PY452/PY452_OH1_Intro.ppt
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?).
Problems with the early Problems with the early - introspective - - introspective -
methods…methods…
Behaviourist’s reactionBehaviourist’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 Behaviourist PsychologyPsychology
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 changeTimes 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 Information Processing Theory 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 Birth of Cognitive PsychologyPsychology
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 PsychologyCognitive Psychology
Stimulus Response
Stimulus Response
SensationPerceptionImageryRetentionRecallProblem-solvingThinking
Behaviourism (1910s-1950s)
Cognitivism (from 1950s)
Black box
General frameworkGeneral framework
© http://lamar.colostate.edu/~bclegg/PY452/PY452_OH1_Intro.ppt
Model of human information processing (Wickens, 1992)
Key conceptsKey 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 Information Processing Analysis ExampleAnalysis Example
http://psych.colorado.edu/~tcurran/psyc2145/lectures/Lec_01_16.pdf
MethodsMethods
(modern) cognitive psychology takes evidence from all 4 areas to try and form an understanding of the human mind
Empirical methods
Cognitive Neuropsychology
Computer modelling
Cognitive Psychology
Cognitive Neuroscience
1. Empirical 1. Empirical methodsmethods
“Cognitive processes and structures are inferred from participants’ behaviour (typically speed
and/or accuracy of performance) obtained under well controlled conditions”
MethodologyMethodology
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 ExperimentSternberg 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 ExperimentSternberg 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 (self-terminating 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)Sternberg's (1969)
What do you expect?
Parallel or serial search?
Exhaustive or self-terminating search?
Sternberg's (1969) Sternberg's (1969) findingsfindings
What do these data show?
Parallel or serial search?(look at positive set, and how RT changes with increasing set size)
Exhaustive or self-terminating?(contrast positive and negative sets)
Sternberg's (1969) Sternberg's (1969) findingsfindings
38 msec per digit
Serial search
Similar RT (reaction times) for positive and negative answers
Exhaustive search
Compare to each item held in memory
Sternberg's (1969) modelSternberg's (1969) model
7
=3?
Make decision
Generate response
38 ms per digit in the memory set
397 ms
Yes
Perceive stimulus =4
?=7?
Input Output
LimitationsLimitations
Indirect information about the internal representations and processes.
Artificial set-up, that rarely corresponds to real-life situations.
2. Cognitive 2. Cognitive NeuropsychologNeuropsycholog
yy
“studies the performance of brain-damaged patients to infer the mechanisms involved -- in
normal cognitive functioning”
Cognitive Cognitive NeuropsychologyNeuropsychology
Example: Semantic vs syntax: Are the processes responsible for generating meaning independent of those responsible for the structure of sentences?
Double dissociation
Based on a Modularity assumption: distinct systems which can suffer damage separately from each other.
Production perfomancesstructuremeaning
Broca
Wernicke
Patients
Broca’s aphasiaBroca’s aphasia
Difficulty speaking (telegraphic speech) with poor syntax (“agrammatical aphasia”) but semantically appropriate words.
Son … university … smart … boy … good … good …
Wernicke’s aphasiaWernicke’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
LimitationsLimitations
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. 3. Computational Computational
modelsmodels(mathematical equations, computer programs, connectionist networks)
Box and Arrows ModelsBox and Arrows Models
Single reaction time model (Newell)
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?”
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 Production systems as computer programscomputer programs
found=0INPUT digit:IF digit = 3 THEN found=1IF digit = 4 THEN found=1IF digit = 7 THEN found=1:IF found = 0 THEN PRINT "not found"
ELSE print "found"
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 networksConnectionist networks
Output Values
Input Signals (External Stimuli)
1. all input neurons are connected to all output neurons
2. 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 Connectionist breakthrough: NETtalkbreakthrough: NETtalk
(Sejnowski & Roseberg, 1986)
Problem of the level of Problem of the level of descriptiondescription
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 4. Cognitive NeuroscienceNeuroscience
“[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”
NeuroscienceNeuroscience
Localisation of brain functions in vivo.
The idea is to look for converging evidence from different approaches
SummarySummary
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)Summary (cntd)
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