2.
Human Cognition Human Computer Interaction
Contents
COGNITIVE PSYCHOLOGY................................................................................................................ 2
COGNITION AND COGNITIVE FRAMEWORKS .............................................................................................. 2
HUMAN INFORMATION PROCESSING ............................................................................................................. 2
THE EXTENDED HUMAN INFORMATION PROCESSING MODEL............................................................. 3
THE MULTI-STORE MODEL OF MEMORY ...................................................................................................... 4
THE MODEL HUMAN PROCESSOR .................................................................................................................... 4
PROBLEMS WITH THE MODEL HUMAN PROCESSOR APPROACH ......................................................... 5
BEYOND THE MODEL HUMAN PROCESSOR .................................................................................................. 5
COMPUTATIONAL VERSUS CONNECTIVIST APPROACHES ..................................................................... 5
DISTRIBUTED COGNITION .................................................................................................................................. 6
Human Computer Interaction: 2. Human Cognition
Cognitive Psychology
The science of psychology has been very influential in Human Computer Interaction. In this
course we will look at some of the main developments and theories in cognitive psychology (the
study of human perception, attention, memory and knowledge), and the ways in which these
have been applied in the design of computer interfaces.
Cognition and Cognitive Frameworks
Cognition is the process by which we gain knowledge. The processes which contribute to
cognition include:
• understanding
• remembering
• reasoning
• attending
• being aware
• acquiring skills
• creating new ideas
A key aim of HCI is to understand how humans interact with computers, and to represent how
knowledge is passed between the two.
The basis for this aspect of HCI is the science of cognitive psychology. The results of work of
cognitive psychologists provide many lessons which can be applied in the design of computer
interfaces. These results are expressed in the form of cognitive frameworks. This section
describes some of the important frameworks which have been developed by psychologists.
Human Information Processing
HCI is fundamentally an information-processing task. The human information processing
approach is based on the idea that human performance, from displayed information to a
response, is a function of several processing stages. The nature of these stages, how they are
arranged, and the factors that influence how quickly and accurately a particular stage operates,
can be discovered through appropriate research methods.
Human information processing analyses are used in HCI in several ways.
• basic facts and theories about information-processing capabilities are taken into
consideration when designing interfaces and tasks
• information-processing methods are used in HCI to conduct empirical studies evaluating
the cognitive requirements of various tasks in which a human uses a computer
• computational models developed in HCI are intended to characterize the information
processing of a user interacting with a computer, and to predict, or model, human
performance with alternative interfaces.
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Human Computer Interaction: 2. Human Cognition
The idea of human information processing is that information enters and exits the human mind
through a series of ordered stages (Lindsay & Norman, 1977), as shown in the figure:
Input Output
Encoding Comparison Response Response
or or
selection execution
stimuli response
Stage 1 Stage 2 Stage 3 Stage 4
The Extended Human Information Processing model
The basic information processing model shown above does not account for the importance of:
• attention the processing only takes place when the human is focussed on the task
• memory the information may be stored in memory and information already in
memory may be used in processing the input
The figure below illustrates the extended human information processing model (Barber 1988). It
shows that attention and memory interact with all the stages of processing
Attention
Input Output
Encoding Comparison Response Response
or or
selection execution
stimuli response
Memory
An important question when researching into memory is how it is structured. Memory can be
broadly categorised into three parts, which have links between them, moving the information
which comes in through the senses.
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Human Computer Interaction: 2. Human Cognition
The Multi-Store model of memory
In 1968, Atkinson and Shiffrin developed a model of memory formed of three 'buffers', which will
store memories and control processes which move information between the buffers. The three
stores identified are:
• sensory information store
• short-term memory (more recently known as working memory)
• long-term memory
External Sensory store Short-term memory Long-term memory
input store store
Lost from sensory Lost from short- Decay,
store term memory store interference and
loss of strength in
long-term memory
store
The Model Human Processor
An important concept from cognitive psychology is the model human processor (MHP) (Card,
Moran, and Newell, 1983). This describes the cognitive process that people go through between
perception and action. It is important to the study of HCI because cognitive processing can have
a significant effect on performance, including task completion time, number of errors, and ease of
use. This model was based on the human information processing model.
The model human processor consists of three interacting systems. Each has its own memory and
processor.
• perceptual processor
o outputs into audio storage
o outputs into visual storage
• cognitive processor
o outputs into working memory.
o has access to:
workingmemory
long term memory
• motor processor
o carries out actions
The MHP model was used as the basis for the GOMS family of techniques proposed by Card,
Moran, and Newell (1983), for quantitatively modeling and describing human task performance.
GOMS stands for Goals, Operators, Methods, and Selection Rules.
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Human Computer Interaction: 2. Human Cognition
Problems with the Model Human Processor approach
• It models performance as a series of processing steps
o is that appropriate?
• It is too focused on one person, one task
• It is an overly simplistic view of human behavior
o ignores environment & other people
Beyond the Model Human Processor
More recent research in cognitive frameworks has focussed on:
• How knowledge is represented
• How mental models are used in HCI
• How users learn and become experienced on systems
• How interface metaphors help to match user’s expectations (and how they don’t!)
• How a person’s mentally-held conceptual model affects behaviour
This represents a change in emphasis from human factors to human actors - a change in focus
on humans from being :passive and depersonalized to active and controlling.
The person is considered as an autonomous agent able to coordinate and regulate behavior,
not a passive element in a human machine system
Computational versus Connectivist Approaches
Cognitive theories are classed as either computational or connectionist.
The computational approach uses the computer as a metaphor for how the brain works, similar
to the information processing models described above.
The connectionist approach rejects the computer metaphor in favour of the brain metaphor, in
which cognition is represent by neural networks. Cognitive processes are characterized as
activation of nodes and connections between them.
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Human Computer Interaction: 2. Human Cognition
Distributed Cognition
Distributed cognition is a framework proposed by Hutchins (1991). Its basis is that to explain
human behavior you have to look beyond the individual human and the individual task. The
functional system is a collection of actors, technology, setting and the interrelations to one
another. Examples of functional systems which have been studied include:
• Ship navigation
• air traffic control
• computer programming teams
The technique is used to analyze coordination of components in the functional system. It
looks at
• information and how it propagates through the system
• how it transforms between the different representational states found in the functional
system
One property of distributed cognition that is often discovered through analysis is situation
awareness (Norman, 1993) which is the silent and inter-subjective communication that is shared
among a group. When a team is working closely together the members will monitor each other to
keep abreast of what each member is doing. This monitoring is not explicit - rather the team
members monitor each other through glancing and inadvertent overhearing
The two main concerns of distributed cognition are:
• To map out how the different representational states are coordinated across time,
location and objects
• To analyze and explain breakdowns
Example:
An electricity power plant was redesigned so that the old system consisting of a single large
display screen which could be seen by all of a team of three operators was replaced by individual
workstation screens for operators. This worked well until there was a problem which resulted in
dangerous gases being released. The team of operators had great difficulty in finding the source
of the problem and deciding what to do.
Because they no longer have access to all the information, they have to spend time explicitly co-
ordinating their understanding of the situation by talking to each other. Under the old system, the
knowledge would be shared – one operator would know what was happening with another’s area
of the plant without explicit communication. Although the team’s individual responsibilities would
still have been clearly divided, the knowledge of the system would be shared.
How could the new system of individual workstations be modified to make better use of
distributed cognition?
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