Human Computer Interaction
4. Attention and Memory
Contents
ATTENTION............................................................................................................................................ 2
FOCUSSING ATTENTION AT THE INTERFACE .............................................................................................. 2
MULTITASKING AND INTERRUPTIONS........................................................................................................... 3
AUTOMATIC PROCESSING .................................................................................................................................. 4
MEMORY CONSTRAINTS...................................................................................................................................... 5
LEVELS OF PROCESSING THEORY ................................................................................................................... 5
MEANINGFUL INTERFACES ................................................................................................................................ 5
MEANINGFULNESS OF COMMANDS ................................................................................................................. 5
MEANINGFULNESS OF ICONS............................................................................................................................. 6
COMBINATION ICONS ........................................................................................................................................... 9
ICONS IN WEB PAGES............................................................................................................................................ 9
INTERFERENCE: THE STROOP EFFECT ........................................................................................................ 11
Human Computer Interaction: 4. Attention and Memory
Attention
The human brain is limited in capacity. It is important to design user interfaces which take into
account the attention and memory constraints of the users. This means that we should design
meaningful and memorable interfaces. Interfaces should be structured to be attention-grabbing
and require minimal effort to learn and remember. The user should be able to deal with
information and not get overloaded.
Our ability to attend to one event from what seems like a mass of competing stimuli has been
described psychologically as focussed attention. The "cocktail party effect" -- the ability to
focus one's listening attention on a single talker among a cacophony of conversations and
background noise---has been recognized for some time.
We know from psychology that attention can be focussed on one stream of information (e.g.
what someone is saying) or divided (e.g. focussed both on what someone is saying and what
someone else is doing). We also know that attention can be voluntary (we are in an attentive
state already) or involuntary (attention is grabbed). Careful consideration of these different states
of attention can help designers to identify situations where a user’s attention may be over-
stretched, and therefore needs extra prompts or error protection, and to devise appropriate
attention attracting techniques.
Sensory processes, vision in particular, are disproportionately sensitive to change and movement
in the environment. Interface designers can exploit this by, say, relying on animation of an
otherwise unobtrusive icon to indicate an attention-worthy event.
Focussing attention at the interface
Techniques which can be used to guide the user’s attention include:
• Structure – grouping, based on the Gestalt laws
• Spatial and temporal cues – where things are positioned or when they appear
• Colour coding, as described in the previous chapter
• Alerting techniques, including animation or sound
Important information should be displayed in a prominent place to catch the user’s eye
Less important information can be relegated to the background in specific areas – the user
should know where to look
Information not often requested should not be on the screen, but should be accessible when
needed
Note that the concepts of attention and perception are closely related.
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Human Computer Interaction: 4. Attention and Memory
Multitasking and Interruptions
In a work environment using computers, people are often subject to being interrupted, for
example by a message or email arriving. In addition, it is common for people to be multitasking -
carrying out a number of tasks during the same period of time by alternating between them. This
is much more common than performing and completing tasks one after another.
In complex environments, users may be performing one primary task which is the most important
at that time, and also one or more less important secondary tasks. For example, a pilot’s tasks
include attending to air traffic control communications, monitoring flight instruments, dealing with
system malfunctions which may arise, and so on. At any time, one of these will be the primary
task, which is said to be foregrounded, while other activities are momentarily suspended.
People are in general good at multitasking but are often prone to distraction. On returning to an
activity, they may have forgotten where they left off. People often develop their own strategies, to
help them remember what actions they need to perform when they return to an activity.
Such external representations, or cognitive aids (Norman, 1992), may include writing lists or
notes, or even tying a knot in a handkerchief.
Cognitive aids have applications in HCI, where the system can be design to provided them –
• the system should inform user where he was
• the system should remind user of common tasks
For example, Amazon’s check out procedure displays a list of steps involved in the process, and
indicates what step has been reached.
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Human Computer Interaction: 4. Attention and Memory
Automatic Processing
Many activities are repeated so often that they become automatic – we do them without any need
to think. Examples include riding a bike, writing, typing, and so on. Automatic cognitive processes
are:
• fast
• demanding minimal attention
• unavailable to consciousness
The classic example used to illustrate the nature of an automatic operation is the Stroop effect.
To experiment with this, look at the colour sheet at the end of this chapter.
This experiment demonstrates interference. The interference between the different information
(what the words say and the colour of the words) your brain receives causes a problem. There
are two theories that may explain the Stroop effect:
• Speed of Processing Theory: the interference occurs because words are read faster than
colors are named.
• Selective Attention Theory: the interference occurs because naming colors requires more
attention than reading words.
If a process is not automatic, it is known as a controlled process.
Automatic processes
• are not affected by limited capacity of brain
• donot require attention
• are difficult to change once they have been learned
Controlled Processes
• are non-automatic processes
• have limited capacity
• require attention and conscious control (Shiffrin & Shneider, 1977)
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Human Computer Interaction: 4. Attention and Memory
Memory Constraints
The human memory system is very versatile, but it is by no means infallible. We find some things
easy to remember, while other things can be difficult to remember. The same is true when we try
to remember how to interact with a computer system. Some operations are simple to remember
while others take a long time to learn and are quickly forgotten.
An understanding of human memory can be helpful in designing interfaces that people will find
easy to remember how to use.
Levels of Processing Theory
The extent to which things can be remembered depends on its meaningfulness. In psychology,
the levels of processing theory (Craik and Lockhart , 1972) has been developed to account for
this. This says that information can be processed at different levels, from a shallow analysis of a
stimulus (for example the sound of a word) to a deep or semantic analysis. The meaningfulness
of an item determines the depth of the processing – the more meaningful an item the deeper the
level of processing and the more likely it is to be remembered.
Meaningful Interfaces
This suggests that computer interfaces should be designed to be meaningful. This applies both to
interfaces which use commands and interfaces which use icons or graphical representations for
actions. In either case, the factors which determine the meaningfulness are:
• Context in which the command or icon is used
• The task it is being used for
• The form of the representation
• The underlying concept
Meaningfulness of Commands
The following guidelines are examples taken from a larger set which was compiled to suggest
how to ensure that commands are meaningful (Booth 1994, Helander, 1988):
• Syntax and commands should be kept simple and natural
• The number of commands in a system should be limited and in a limited format
• Consider the user context and knowledge when choosing command names.
• Choose meaningful command names. Words familiar to the user
• The system should recognize synonymous and alternative forms of command syntax
• Allow the users to create their own names for commands
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Human Computer Interaction: 4. Attention and Memory
Sometimes a command name may be a word familiar to the user in a different context. For
example, the word ‘CUT’ to a computer novice will mean to sever with a sharp instrument, rather
than to remove from a document and store for future use. This can make the CUT command
initially confusing.
Meaningfulness of Icons
Icons can be used for a wide range of functions in interfaces, for example
• Labeling e.g. toolbar item, web page link
• Warning e.g. error message
• Identifying e.g. file types, applications
• Manipulating e.g. tools for drawing, zooming
• Container e.g. wastebasket, folder
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Human Computer Interaction: 4. Attention and Memory
The extent to which the meaning of an icon is understood depends on how it is represented.
Representational form of icons can be classified as follows:
Resemblance icons – depict the underlying concept through an analogous image.
the road sign for "falling rocks" presents a clear resemblance of the roadside hazard.
this represents the Windows calculator application, and resembles a calculator
Exemplar icons – serve as a typical example
a knife and fork used in a public information sign to represent "restaurant services". The image
shows the most basic attribute of what is done in a restaurant i.e. eating.
this represents Microsoft Outlook – the clock and letter are examples of the tasks this application
does (calendar and email tasks)
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Human Computer Interaction: 4. Attention and Memory
Symbolic icons – convey the meaning at a higher level of abstraction
the picture of a wine glass with a fracture conveys the concept of fragility
this represents a connection to the internet – the globe conveys the concept of the internet
Arbitrary icons – bear no relation to the underlying concept
the bio-hazard sign consists of three partially overlaid circles
this represents a software design application called Enterprise Architect. There is no obvious
meaning in the icon to tell you what task you can do with the application
Note that arbitrary icons should not be regarded as poor designs, even though they must be
learned. Such symbols may be chosen to be as unique and/or compact such as a red no entry
sign with a white horizontal bar, designed to avoid dangerous misinterpretation.
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Human Computer Interaction: 4. Attention and Memory
Combination Icons
Icons are often favoured as an alternative to commands. It is common for users who use a
system infrequently to forget commands, while they are less likely to forget icons once learnt.
However, the meaning of icons can sometimes be confusing, and it is now quite common to use a
redundant form of representation where the icons are displayed together with the command
names.
The disadvantage of this approach is that it takes up more screen space. This can be reduced by
using pop-up tool tips to provide the text.
Icons in Web Pages
The use of graphical representation in web pages tends to be quite different to that in other
interfaces. Most user actions (links) are usually represented by text (although the text may
actually be an image).
There is often isolated and specific use of icons and graphical representations for links. The
following examples are from amazon.co.uk.
• Buttons to submit forms, e.g. search boxes:
• Images of items - the user can click to get more information on the item :
• Links to specific site features, e.g. shopping basket:
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Human Computer Interaction: 4. Attention and Memory
Icon use in web pages is sparing for a number of reasons, for example:
• Pages often convey information and branding graphically, so it would be difficult to focus
attention on icons among other graphical content.
• Graphical links are often banners to focus attention to a small number of specific items
• The web browser has its own set of icons
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Human Computer Interaction: 4. Attention and Memory
Interference: The Stroop Effect
Don't read the words below—just say the colours they're printed in, and do this
aloud as fast as you can.
If you're like most people, your first inclination was to read the words, 'red, yellow, green...,' rather than
the colours they're printed in, 'blue, green, red...'
You've just experienced interference.
When you look at one of the words, you see both its colour and its meaning. If those two pieces of
evidence are in conflict, you have to make a choice. Because experience has taught you that word
meaning is more important than ink colour, interference occurs when you try to pay attention only to the
ink colour.
The interference effect suggests you're not always in complete control of what you pay attention to.
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