Chapter 7
Psychology: Memory
By the end of this lecture
you should know...
• About developments in psychology
• About cognitive psychology in particular
– The mind as information processor
• About the model human processor
• About how MHP can be used in the
design of interactive systems
7.1 Introduction
• If you want to develop effective, interactive systems, then
you need a fundamental understanding of your users’
psychology
• Cognitive psychology:
– is an advanced branch of psychology,
– is relevant to ICT and
– allows us to understand how people perceive, retain and use
information to perform mental or cognitive tasks
• Model Human Processor (MHP)
– Is a theory of cognitive psychology that
– seeks to specify the information processing demands on and of
users
• Aim of MHP
– Designs system that are compatible with their users
– Evaluate existing systems and their variants
– Make quantitative predictions about their use
7.2 Psychology: Memory
• Idea of psychological theory is that it explains and
predicts human behaviour
• We use a model to present such a theory
• Given a model of
(i) how a computer system behaves,
(ii) the required tasks and
(iii) the users’ behaviour
we can predict the behaviour of the whole interactive
system
• A model allows us to design an interactive system to be
more usable without having to test it directly on a large
number of users.
7.3 Background psychology
• Freud
– Psychology is popularly associated with Sigmund Freud and
his psychoanalysis
– Modern psychologists still refer to his work although his
methods was not quite scientific
– He established the complexity of the human mind
• Humans need to be considered in terms of emotions,
motivations, cognition & rational thinking
• Behaviourism
– Pavlov and his dog
– Shows a link between input (stimuli) and output (response)
• Association or reward could condition human & animal behaviour.
– Measuring behaviour is more objective than asking someone
to describe what they are doing
• Neuropsychology
– The brain is made up of a network of 10 billion neurons
– Over 100 billion billion possible interconnections
– Human behaviour is emergent from the complexity of the interconnections –
from the application of a set of simple rules
– Challenge: How do we discover at least some of these rules?
7.4 Cognitive psychology
Cognitive Psychology builds on strengths of four approaches:
• Following Freud, it accepts the complexity of human cognition
and the need to consider a combination of cognition,
emotions and motivation & rational thinking
• Like behaviourism, looks at stimuli and responses
– Also describes internal mechanisms that give rise to behaviour
• Artificial Intelligence (AI)
– Based on early computer simulation work
– If you can program a computer to behave intelligently, then you must
have some idea of what intelligence is
• Phenomenology
– Emphasises people’s subjective experiences and seeks to relate
existing behaviour and experience
Cognitive Psychology
Cognitive Psychology
= Overall approach to understanding
human performance and related issues.
Applied cognitive science
= directed to the solution of real-world
problems, e.g. design of interactive
systems / websites
Understanding how
users think
Example 1
• Which of these are easiest to remember?
– “7935” or “4359810350703981”
– “0020-2-735-8888” or “469268731056”
– “djsgmpukhszqplmyobkjktj” or
“the quick brown fox jumps over the lazy
dog”
Why?
Example 2
GREEN
BLUE
• Read the words aloud. How
difficult is it not to say the
colour rather than the word?
• Experiments have shown
that even simple changes in
what is expected can cause
significant difficulties in
interpretation.
BLACK
YELLOW
ORANGE
GREY
PIENK
RED
GREEN
BLACK
These examples….
• May not be directly relevant to computer
system design, but
• Indicate something about how our minds
work
– Highlight some of the things people find difficult
and things people find easy
• Such knowledge can inform the way we
design usable user interfaces
Chunking Example
Can you memorise the letters?
A Z M B X N C Y L
Chunking Example
And these?
AZM BXN CYL
Chunking Example
And these?
ABC
LMN
XYZ
7.5 The model human
processor (MHP)
Response
Long term memory
Cognitive
processing
Short term memory
Perception
MHP (continued)
• MHP was the first simplistic theory of human
cognition
• It models people as information processors
with particular characteristics and abilities
• Was never intended to be a full & detailed
theory of Psychology (although sometimes
criticized as if it were)
• Was intended as a simplistic theory to guide
and illuminate good practice in ICT
Working memory limits
MHP: properties of STM to model and
predict human performance
• Decay time: 10-20s
– Maintained and increased with rehearsal
• Size: It can hold 7  2 items
– What is an item?
• A ‘chunk’ of information, e.g. a word, letter,
meaningful sentence, logically grouped items
– bjsncvfqwlr
– the quick brown fox jumped over the lazy dog
• Size of chunks – small influence on memory
Long term memory
(LTM)
LTM different properties to STM
• Organised as a network of connected “chunks” of
knowledge
– Facts
– Definitions
– Meanings
– Procedures
• Recall from LTM with aid of:
– recollection
– association
– And by matching with available information
Recognition and recall
• Different forms of
remembering:
• Example:
– Use of icons (recognition)
– recognition
• stimulus allows
retrieval from LTM
– recall
• no stimulus; may
involve a “search”
• Guidelines such as
– “Use recognition
instead of recall”
vs.
key combinations (recall)
• Control-X, Control-C,
Control-V
Practical Memory guidelines
based on STM & LTM
strengths and weaknesses
• Support recognition rather than recall
• Reduce working memory load
• Support chunking by structuring
information to facilitate memory
• Frequent activities become automatic
and so don’t require conscious attention
Simplex One
MHP has led to a number of more advanced simplistic
theories such as Simplex. Simplex One is typical of
current views of the architecture of human cognition.
• Refer to ch 2, p30.
Consequences of Simplex
One approach for Interactive
Systems Design
• An interactive system must provide suitably designed input to
the user (input store)
• A well-designed system must support the user’s responses
and allow them to be made easily (motor output store)
• A system should not require an excessive amount of
information to be stored in working memory
• A system should provide the user with appropriate information
for long-term associative store or long-term memory use, in
the correct form and so that learning may be optimised
• The system should support the executive or processing
system by ensuring that the tasks are required by the system
are not too complex to be mastered and maintained.