COGNITIVE PROCESS: ATTENTION, MEMORY, REVISED MEMORY MODEL

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Human Computer Interaction (CS408)

Lecture

Lecture 9. Cognitive Process - Part I

Learning Goals

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:

Attention

Memory

Perception and recognition

Learning

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

Attention

Encoding

Comparison

Response

Selection

Execution

Memory

9.1 Attention

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

the range of possibilities available.

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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

street.

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.

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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

carrying

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

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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

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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 multi-

store 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),

Sensory memory

Short-term memory store holds limited

information for a short period of time (a few

seconds),

Permanent long-term memory store hold

Short term

information indefinitely.

Lets us have a detailed look of this model.

memory

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

Long term

stimuli, echoic memory for aural stimuli and haptic

memory

memory for touch. These memories are constantly

overwritten by new information coming in on these

channels.

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

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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 7±2 digits. This

was established in experiments by Miller. Try it look at the following number

sequence:

54988319814237

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 7±2 rule is that we can remember 7±2 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

information.

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

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procedural rules of behavior- in fact, everything that we know. It differs from short-

term 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

days.

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

knowledge.

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COLLIE

DOG

Fixed

breed of: DOG

Fixed

type: sheepdog

legs: 4

Default

size: 65 cm

diet: carniverous

sound: bark

Variable

colour

Variable

Script for a visit to

size:

the vet

Roles:

vet examines

Entry conditions: dog ill

diagnoses

vet open

treats

owner has

owner brings dog in

money

pays

takes dog out

Result:

dog better

owner poorer

Scenes:

arriving at reception

vet richer

waiting in room

examination

Props:

examination table

paying

medicine

instruments

Tracks:

dog needs medicine

dog needs operation

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9.3 Revised Memory Model

According to revised memory model Working memory is a subset of LTM.

Some other characteristics are as under:

Items are semantically linked.

Items in working memory are activated.

Activation is supplied from other linked chunks and from sensory input.

As we know human processor consists of three interacting systems: the perceptual

system, the motor system and the cognitive system. Each has its own memory and

process as shown in figure. Similar to the notions of human information processing,

human performance is viewed as a series of processing stages, whereby the different

processors and memories are organized in a particular way.

Visual Stimulus

Perceptual processor

Visual image

Auditory

store

image store

Motor processor

Working memory

Cognitive Processor

Long-term memory

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