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Human Computer Interaction

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As the aim of this lecture is to introduce you the study of Human Computer
Interaction, so that after studying this you will be able to:
Understand attention
Describe memory models
To day is first lecture on cognitive processes out series of two lectures on the same
topic. In our previous lectures we have in detail talked about the cognitive psychology
and cognitive frame works. Now is this lecture and in next coming lectures we will
talk about a detail about the cognitive processes. As we have already discussed that
cognition can be described in terms of specific kinds of processes. These include:
Perception and recognition
Reading, speaking and listening
Problem solving, planning, reasoning, decision-making.
Here in this lecture we will study the first two cognitive processes named attention
and memory. The importance of these two you have seen in the Extended Human
Processing model, studied in Lecture No. 6, as shown in figure

9.1 Attention

Attention is the process of selecting things to concentrate on, at a point in time, from
the range of possibilities available.


A famous psychologist, Williams James says, “ Everyone knows what attention is. It
is the taking possession of mind, in clear and vivid form, of one out of what seem
several simultaneously possible objects or trains of thought… it requires withdrawal
from some things in order to deal effectively with others.”
Attention involves our auditory and/or visual senses an example of auditory attention
is waiting in the dentist’s waiting room for our name to be called out to know when it
is our time to go in. auditory attention is based on pitch, timber and intensity. An
example of attention involving the visual senses in scanning the football results in a
newspaper to attend to information about how our team has done. Visual attention is
based on color and location.
Attention allows us to focus on information that is relevant to what we are doing. The
extent to which this process is easy or difficult depends on
Whether we have clear goals and
Whether the information we need is salient in the environment.
Our goals
If we know exactly what we want to find out, we try to match this with the
information that is available. For example, if we have just landed at an airport after a
long flight and want to find out who has won the World Cup, we might scan the
headlines at the newspaper stand, check the web, call a friend, or ask someone in the
When we are not sure exactly what we are looking for we may browse through
information, allowing it to guide our attention to interesting or salient items. For
example, when we go to restaurant we may have the general goal of eating a meal but
only a vague idea of what we want to eat. We peruse the menu to find things that whet
our appetite, letting our attention be drawn to the imaginative descriptions of various
dishes. After scanning through the possibilities and imagining what each dish might
be like (plus taking into account other factors, such as cost, who we are with, what the
specials are, what the waiter recommends, whether we want a two-or- three-course
meal, and so on.), we may then make a decision.
Information presentation
The way information is displayed can also greatly influence how easy or difficult it is
to attend to appropriate pieces of information. Look at the figure below, two different
ways of structuring the same information at the interface: one makes it much easier to
find information than the other. Look at the top screen and (i) find the price for a
double room at the Holiday Inn in Lahore: (ii) find the phone number of the Sheraton
in the Karachi. Then look at the bottom screen and (i) find the price of for a double
room at the Pearl Continental in Faisalabad; (ii) find the phone number of the Holiday
Inn in the Islamabad. Which took longer to do. Experiments showed that the two
screens produced quite different results: it took an average of 3.2 seconds to search
the top screen and 5.5 seconds to find the same kind of information in the bottom
screen. Why is this so, considering that the both displays have the same density of
information? The primary
reason is the way the characters are grouped in the display; in the top they are grouped
into vertical categories of information that have columns of space between them. In
the bottom screen the information is bunched up together, making it much harder to
search through.

Models of Attention
There are two models of attention:

 Focused attention

 Divided attention
Focused Attention
Our ability to attend to one event from what amounts to a mass of competing stimuli
in the environment have been psychologically termed as focused attention. The
streams of information we choose to attend to will tend to be relevant to the activities
and intentions that we have at that time. For example, when engaged in a conversation
it is usual to attend to what the other person is saying. If something catches our eye in
the periphery to our vision, for example, another person we want to talk to suddenly
appear, we may divert our attention to what she is doing. We may then get distracted
from the conversation we are having and as a consequence have to ask the person we
are conversing with to repeat themselves. On the other hand, we may be skilled at
on the conversation while intermittently observing what the person we want to talk to
is doing.
Divided Attention
As we said, we may be skilled at carrying on the conversation while intermittently
observing what the person we want to talk to is doing. When we attempt to attend to
mire than one thing at a time, as in the above example, it is called divided attention.
Another example that is often used to illustrate this attentional phenomenon is being
able to drive while holding a conversation with a passenger.
Voluntary attention
A further property of attention is that can be voluntary, as when we make a conscious
effort to change our attention.
Involuntary attention

Attention may also be involuntary, as when the salient characteristics of the
competing stimuli grab our attention. An everyday example of an involuntary act is
being distracted from working when we can hear music or voices in the next room.
Another thing is that frequent actions become automatic actions, that is, they do not
need any conscious attention and they require no conscious decisions.
Focusing attention at the interface
What is the significance of attention for HCI? How can an understanding of
attentional phenomena be usefully applied to interface design? Clearly, the manner in
which we deploy our attention has a tremendous bearing on how effectively we can
interact with a system. If we know that people are distracted, often involuntarily, how
is it possible to get their attention again without allowing them to miss the ‘window of
opportunity’? Moreover, how can we focus people’s attention on what they need to be
looking at or listening to for any given stage of task? How can we guide their
attention to the relevant information on display?
Structuring Information
One way in which interfaces can be designed to help users find the information they
need is to structure the interface so that it is easy to navigate through. Firstly. This
requires presenting not too much information and not too little o a screen, as in both
cases the user will have to spend considerable time scanning through either a cluttered
screen or numerous screens of information. Secondly, instead of arbitrarily presenting
data I the screen it should be grouped and ordered into meaningful parts capitalizing o
the perceptual laws of grouping, information can be meaningfully structured so that it
is easier to perceive and able to guide attention readily to the appropriate information.
Help user to.
attend his/her task not the interface.
decide what to focus on, based on their tasks, interest, etc.
stay focused, do not provide unnecessary distractions.
structure his/her task, e.g. help
Create distraction, when really necessary!
Use alerts (only) when appropriate!
Some other considerations are as under:
Make information salient when it needs attending to
Use techniques that make things stand out like colour, ordering, spacing, underlining,
sequencing and animation
Avoid cluttering the interface - follow the google.com example of crisp, simple design
Avoid using too much because the software allows it

9.2 Memory

Indeed, much of our everyday activities rely on memory. As well as storing all our
factual knowledge, our memory contains our knowledge of actions or procedures. It
allows us to repeat actions, to use language, and to use new information received wia
our senses. It also gives us our sense of identity, by preserving information from our
past experiences. If want to understand the working of our memory, it is necessary to
understand the structure of memory. Let us look at a memory model.
Memory Model

It is generally agreed that there are three types of memory or memory functions
sensory buffers, short-term memory or working memory and long-term memory. It is
also called the multi-store model of memory. The main characteristics of the multistore
model of memory are the various types of memory stores. These are:

Sensory store modality-specific, hold
information for a very brief period of time (a few
tenth of a second),

Short-term memory store holds limited
information for a short period of time (a few

Permanent long-term memory store hold
information indefinitely.
Lets us have a detailed look of this model.
Sensory memory
The sensory memories act as buffer for stimuli
received through the senses. A sensory memory exists
for each sensory channel: iconic memory for visual
stimuli, echoic memory for aural stimuli and haptic
memory for touch. These memories are constantly
overwritten by new information coming in on these
We can demonstrate the existence of iconic memory by moving a finger in front of
the eye. Can you see it in more than one place at once? This indicates a persistence of
the image after the stimulus has been removed. A similar effect is noticed most
vividly at firework displays where moving sparklers leave a persistent image.
Information remains in iconic memory very briefly, in the order of 0.5 seconds.
Similarly, the existence of echoic memory is dvidenced by our ability to ascertain the
direction from which a sound originates. This is due to information being received by
both ears. However, since this information is received at different times, we must
store the stimulus in the meantime. Echoic memory allows brief playback of
information. Have you ever had someone ask you a question when you are reading?
You ask them to repeat the question only to realise that you know what was asked
after all. This experience, too, is evidence of the existence of echoic memory.
Information is passed from sensory memory into short-term memory by attention,
thereby filtering the stimuli to only those, which are of interest at a given time.
Attention is the concentration of the mind on one out of a number of competing
stimuli or thoughts. It is clear that we are able to focus our attention selectively,
choosing to attend to one thing rather than another. This is due to the limited capacity
of our sensory and mental processes. If we did not selectively attend to the stimuli
coming into our senses, we would be overloaded. We can choose which stimuli to
attend to, and the choice is governed to an extent by our arousal, our level of interest
or need. This explains the cocktail party phenomenon. According to cocktail party
effect we can attend to one conversation over the background noise, but we may
choose to switch our attention to a conversation across the room if we hear our name
mentioned. Information received by sensory memories is quickly passed into a more
permanent memory store, or overwritten and lost.
Short term memory

Sensory memory

Short term

Long term

Short-term memory or working memory acts as a scratch pad for temporary recall of
information. It is use to store information which is only required fleetingly. For
example, calculate the multiplication 35 * 6 in your head. The chances are that you
will have done this calculation in staged, perhaps 5 * 6 and then 3 * 6 and added the
results. To perform calculations such as this we need to store the intermediate stages
for use later. Or consider reading. In order to comprehend this sentence you need to
hold in your mind the beginning of the sentence as you read the rest. Both of these
tasks use short-term memory.
Short-term memory can be accessed rapidly, in the order of 70ms. However, it also
decays rapidly, meaning that information can only be held there temporarily, in the
order of 200ms.
Short-term memory also has a limited capacity. There are two basic methods for
measuring memory capacity. The first involves determining the length of a sequence,
which can be remembered in order. The second allows items to be freely recalled in
any order. Using the first measure, the average person can remember 72 digits. This
was established in experiments by Miller. Try it look at the following number
Now write down as much of the sequence as you can remember. Did you get it all
right? If not, how many digits could you remember? If remembered between five and
nine digits your digits your digit span is average.
Now try the following sequence:
22 55 36 8998 30
did you recall that more easily? Here the digits are grouped or chunked. A
generalization of the 72 rule is that we can remember 72 chunks of information.
Therefore chunking information can increase the short-term memory capacity. The
limited capacity of short-term memory produces a subconscious desire to create
chunks, and so optimise the use of the memory. The successful formation of a chunk
is known as closure. This process can be generalized to account for the desire to
complete or close tasks held in short-term memory. If a subject fails to do this or is
prevented from doing so by interference, the subject is liable to lose trick of what she
is doing and make consequent errors.
Recency effect
In experiments where subjects were able to recall works freely, evidence shows that
recall of the last words presented is better than recall of those in the middle. This is
known as recency effect. Recency effect can be defined as: ‘better recall for items at
the end of the list because these items are still active in STM (and possibly SM) at
time of recall’.
However, if the subject is asked to perform another task between presentation and
recall the recency effect is eliminated. The recall of other words is unaffected. This
suggests that short-term memory recall is damaged by interference of other
Primacy effect
‘Better recall for items at the beginning of the list (because these items have been
rehearsed more frequently than other items and thus have a greater chance of being
placed in LTM).’
Long Term Memory
If short-term memory is our working memory or ‘scratch-pad’, long-term memory is
our main resource. Here we store factual information, experiential knowledge, and

procedural rules of behavior- in fact, everything that we know. It differs from shortterm
memory in a number of significant ways. First, it has a huge, if not unlimited,
capacity. Secondly, it has a relatively slow access time of approximately a tenth of a
second. Thirdly, forgetting occurs more slowly in long-term memory, if at all.
Long-term memory is intended for the long-term storage of information. Information
is placed there from working memory through rehearsal. Unlike working memory
there is little decay: long-term recall after minutes is the same as that after hours or
Long-term memory structure
There are two types of long-term memory: episodic memory and semantic memory.
Episodic memory
Episodic memory represents our memory of events and experiences in a serial form. It
is from this memory that we can reconstruct the actual events that took place at a
given period of our lives.
Semantic memory
Semantic memory is structured record of facts, concepts and skills that we have
acquired. The information in semantic memory is derived from that in our episodic
memory, such that we can learn new facts or concepts from our experience.
Semantic memory is structured in some way to allow access to information,
representation of relationships between pieces of information, and inference. One
model for the way in which semantic memory is structured is as a network. Items are
associated to each other in classes, and may inherit attributes from parent classes. This
model is known as a semantic network. As an example, knowledge about dogs may be
stored in a network such as that shown in figure.
Specific breed attributes may be stored with each given breed, yet general dog
information is stored at a higher level. This allows us to generalize about specific
cases. For instance, we may not have been told that the sheepdog Shadow has four
legs and a tail, but we can infer this information from our general knowledge about
sheepdogs and dogs in general. Note also that there are connections within the
network which link into other domains of knowledge, for example cartoon characters
A number of other memory structures have been proposed to explain how we
represent and store different types of knowledge. Each of these represents a different
aspect of knowledge and, as such, the models can be viewed as complementary rather
than mutually exclusive. Semantic networks represent the associations and
relationship between single items in memory. However, they do not allow us to model
the representation of more complex objects or events, which are perhaps composed of
a number of items of activities. Structured representations such as frames and scripts
organize information into data structures. Slots in these structures allow attribute
values to be added. Frame slots may contain default, fixed or variable information. A
frame is instantiated when the slots are filled with appropriate values. Frame and
scripts can be linked together in networks to represent hierarchical structured

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