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