Unidad IV Ingenier a Cognitiva

Copyright 2006 John Wiley & Sons, Inc

Chapter IV– Cognitive

Engineering

[1] HCI: Developing Effective Organizational Information Systems, Dov Te’eni, Jane Carey, Ping Zhang

[2] Interaction Design: Beyond Human-Computer Interaction, Yvonne Rogers, Helen Sharp, Jennifer Preece


Introduction [1]

Cognitive engineering applies knowledge of cognitive psychology to the design and development of systems that support the cognitive processes of users.

A simplified cognitive model of human information processing serves as the basis for understanding how cognitive resources such as memory and attention are utilized in HCI.

Additional models such as Norman’s model of user activity and the GOMS model further demonstrate how user interact with computers and the implications for designers.

Complexity is seen to represent the utilization of scarce cognitive resources and reducing complexity is one of the goals of cognitive engineering.


A Simplified View of Human

Information Processing (HIP) [1]

Figure 5.3 presents a simplified model of Human

Information Processing which includes processors

and memories that interact in order to process

information.

There are three types of processors:

Perceptual,

Cognitive, and

Motor processors.

Two types of memory:

Working memory

Long-term memory




Figure 5.3 A simplified model of Human Information Processing (HIP),

including memories and processor.

MemoryProcessors

Working

Memory

Perception Motor

Verbal

Cognition

Attention

Memory

Working

Memory

Perception

Spatial

data

Long term

Memory

MemoryProcessors

Working

Memory

Perception Motor

Verbal

Cognition

Attention

Memory

Working

Memory

Perception

Spatial

data

Long term

Memory




Performance: the speed and accuracy of the

information-processing task.

Automatic behavior: behavior characterized

by cognitive processes that are fast and

cognitively undemanding.

Controlled behavior: behavior characterized

by cognitive processes that are relatively slow

and cognitively demanding.




Processing of Images: processing characterized as spatial, graphic, and holistic.

Processing of verbal information: processing characterized as sequential, linguistic, and procedural.

Memory Aids

Heuristics: rules of thumb that depend heavily on the content and context of the task.

Metaphor: a cognitive process in which an experience is related to an already familiar concept.

Mental model: a representation of the conceptual structure of a device or a system.

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Why do we need to understand users? [2]

Interacting with technology is cognitive

Need to take into account cognitive processes involved and cognitive limitations of users

Provides knowledge about what users can and cannot be expected to do

Identifies and explains the nature and causes of problems users encounter

Supply theories, modelling tools, guidance and methods that can lead to the design of better interactive products

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Cognitive processes [2]

Attention

Perception and recognition

Memory

Learning

Reading, speaking and listening

Problem-solving, planning, reasoning and decision-

making

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Attention [2]

Selecting things to concentrate on at a point in time from the mass of stimuli around us

Allows us to to focus on information that is relevant to what we are doing

Involves audio and/or visual senses

Focussed and divided attention enables us to be selective in terms of the mass of competing stimuli but limits our ability to keep track of all events

Information at the interface should be structured to capture users’ attention, e.g. use perceptual boundaries (windows), colour, reverse video, sound and flashing lights

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Activity: Find the price of a double room at the Holiday Inn

in Bradley [2]

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Activity: Find the price for a double room at the Quality Inn

in Columbia [2]

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Activity [2]

Tullis (1987) found that the two screens produced quite different results 1st screen - took an average of 5.5 seconds to search

2nd screen - took 3.2 seconds to search

Why, since both displays have the same density of information (31%)?

Spacing In the 1st screen the information is bunched up together,

making it hard to search

In the 2nd screen the characters are grouped into vertical categories of information making it easier


The Complexity of HCI [1]

Complexity of HCI: the

human resources

needed for interacting

with the computer to

accomplish the task.

Figure 5.4 HCI as a Bridge between Human and Computer


Gulfs of Execution and Evaluation

[1]

Gulf of execution: the gap between the

user’s goal and its computerized

implementation.

Gulf of evaluation: the gap between the

computerized implementation of the user’s

goal and its evaluation by the user.


Bridging the gaps using Norman’s

Model [1]

Figure 5.6 Norman's seven stage model of

user activity

•Establish a goal that needs to be

accomplished.

•Form the intention (or hierarchy of

intentions) that will accomplish the goal.

•Specify the action sequence to

implement the intentions.

•Execute the action.

•Perceive the state of system resulting

from the action.

•Interpret the system state.

•Evaluate your interpretation against

the expectation based on your

intentions.

Goals

Intentions Evaluation

Action

specificationInterpretation

Execution Perception

Physical

system


Fit and Complexity [1]

The fit between the user’s mental model of

the system and the actual model of the

system affects complexity, too. The greater

the fit, the easier it is to determine how to

translate goals into action. The greater the

misfit, the more difficult and more erroneous

is the process of bridging the execution and

evaluation gulfs.


User Activity with Multiple Intentions[1]

Users in organizational settings usually interact with

computers to achieve complex goals.

Norman’s model of user activity can be useful for

describing the user activity involved in more complex

tasks by modelling multiple intentions to accomplish a

single goal, (e.g. checking a new sales forecast and

summing the corresponding revenues).

Each of these two intentions describes how the

seven stages are organized to bridge the gulfs

between the computer and the user.


Causes of Errors [1]

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Perception [2]

How information is acquired from the world and

transformed into experiences

Obvious implication is to design representations that

are readily perceivable, e.g.

Text should be legible

Icons should be easy to distinguish and read

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Is color contrast good? Find italian [2]

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Are borders and white space

better? Find french [2]

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Activity [2]

Weller (2004) found people took less time to

locate items for information that was grouped

using a border (2nd screen) compared with using

color contrast (1st screen)

Some argue that too much white space on

web pages is detrimental to search

Makes it hard to find information

Do you agree?

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Which is easiest to read and why?

[2]

What is the time?

What is the time?

What is the time?

What is the time?

What is the time?

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Design implications [2]

Icons should enable users to readily distinguish their meaning

Bordering and spacing are effective visual ways of grouping information

Sounds should be audible and distinguishable

Speech output should enable users to distinguish between the set of spoken words

Text should be legible and distinguishable from the background

Tactile feedback should allow users to recognize and distinguish different meanings

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Memory [2]

Involves first encoding and then retrieving knowledge

We don’t remember everything - involves filtering and processing what is attended to

Context is important in affecting our memory (i.e. where, when)

We recognize things much better than being able to recall things

2. Number of Elements in an

Interface

21/01/2014 (Adapted from Pressman 2005 and Stallings 2005) 26

21/01/2014 27 © Juan Manuel Gómez Reynoso, Ph.D.

(Adapted from Pressman 2005 and

Stallings 2005)

Human factors in interface design

Limited short-term memory People can instantaneously remember about 7 items of

information. If you present more than this, they are more liable to make mistakes.

People make mistakes When people make mistakes and systems go wrong,

inappropriate alarms and messages can increase stress and hence the likelihood of more mistakes.

People are different People have a wide range of physical capabilities. Designers

should not just design for their own capabilities.

People have different interaction preferences Some like pictures, some like text.

21/01/2014 28 © Juan Manuel Gómez Reynoso, Ph.D.

(Adapted from Pressman 2005 and

Stallings 2005)

People’s Mind

People learn through mental models

A mental model is acquired through the

intervention of the 3 levels of memory

Long term memory: retrieve

Short term memory: perceive. Short-term

memory (STM) refers to memories that last no

longer than 30 seconds unless they are

rehearsed in that timeframe.

Working memory: put together pieces, then

store

Memory Span

The exact reasons for forgetting information over a

short period of time are disputed

The general consensus is that the amount of new

facts we can retain over short periods of time are

severely restricted by this process of forgetting.

Another term for the capacity of short-term memory is

'memory span'.

A memory span test consists of the individual

conducting the experiment reading out lists of words

or digits which increase in length. The longest list a

person can remember in the correct order in over half

the trials is known as his or her memory span.

Chunking

A method of improving our ability to remember things over a

short period of time is called chunking.

This is also a word used to describe the organization of things

into meaningful sections.

Realistically, the average person under normal conditions can

expect to remember four items short-term. With chunking, it is

possible to remember far more.

For example, it is easier to remember nine numbers in three

groups of three.

The total capacity of short-term memory is hard to define

because it will be different depending on the material used.

Generally speaking however, short-term memory can be

affected by long term memory, time taken to pronounce words

and differences between individuals


21/01/2014 31© Juan Manuel Gómez Reynoso, Ph.D.

(Adapted from Pressman 2005 and Stallings

2005)

Learning Model

Auto

Human’s mind is able to detect 7 ± 2 elements at the same time

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Processing in memory [2]

Encoding is first stage of memory determines which information is attended to in the

environment and how it is interpreted

The more attention paid to something…

The more it is processed in terms of thinking about it and comparing it with other knowledge…

The more likely it is to be remembered e.g. when learning about HCI, it is much better to reflect

upon it, carry out exercises, have discussions with others about it, and write notes than just passively read a book, listen to a lecture or watch a video about it

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Context is important [2]

Context affects the extent to which information can be subsequently retrieved

Sometimes it can be difficult for people to recall information that was encoded in a different context: “You are on a train and someone comes up to you and says

hello. You don’t recognize him for a few moments but then realize it is one of your neighbors. You are only used to seeing your neighbor in the hallway of your apartment block and seeing him out of context makes him difficult to recognize initially”

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Activity [2]

Try to remember the dates of your grandparents’ birthday

Try to remember the cover of the last two DVDs you bought or rented

Which was easiest? Why?

People are very good at remembering visual cues about things e.g. the color of items, the location of objects and marks on an

object

They find it more difficult to learn and remember arbitrary material e.g. birthdays and phone numbers

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Recognition versus recall [2]

Command-based interfaces require users to recall from memory a name from a possible set of 100s

GUIs provide visually-based options that users need only browse through until they recognize one

Web browsers, MP3 players, etc., provide lists of visited URLs, song titles etc., that support recognition memory

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The problem with the classic ‘72’

[2]

George Miller’s (1956) theory of how much

information people can remember

People’s immediate memory capacity is very

limited

Many designers think this is useful finding for

interaction design

But…

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What some designers get up to…[2]

Present only 7 options on a menu

Display only 7 icons on a tool bar

Have no more than 7 bullets in a list

Place only 7 items on a pull down menu

Place only 7 tabs on the top of a website page But this is wrong? Why?

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Why? [2]

Inappropriate application of the theory

People can scan lists of bullets, tabs, menu items for the one they want

They don’t have to recall them from memory having only briefly heard or seen them

Sometimes a small number of items is good

But depends on task and available screen estate

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Personal information management [2]

Personal information management is a growing problem for many users vast numbers of documents, images, music files, video clips,

emails, attachments, bookmarks, etc.,

where and how to save them all, then remembering what they were called and where to find them again

naming most common means of encoding them

but can be difficult to remember, especially when have 1000s and 1000s

How might such a process be facilitated taking into account

people’s memory abilities?

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Personal information management

[2]

Memory involves 2 processes recall-directed and recognition-based scanning

File management systems should be designed to optimize both kinds of memory processes e.g. Search box and history list

Help users encode files in richer ways Provide them with ways of saving files using colour, flagging,

image, flexible text, time stamping, etc


The GOMS Model for Describing HCI[1]

GOMS: Goals, Operators, Methods, and Selection rules are the elements of a model that describes purposeful HCI.

Goals specify what the user wants and intends to achieve.

Operators are the building blocks for describing human-computer interaction at the concrete level.

Methods are programs built with operators that are designed to accomplish goals.

Selection rules predict which method will be used. For example, “If the mouse is working, select ‘point to an item on screen’, if not select ‘choose OPEN option in file menu’”.

GOMS Architecture


Using GOMS [1]

Repeat

until

Satisfied

Choose Top Level Goals

Start

Draft Operators and

Methods for Each Goal

Select Methods

Check for Goal Attainment

Further

Refinement

Needed?

Stop

No

Yes

Figure 5.9 A flow chart for building GOMS

Example: Check email

Procedure check_emails Goal Login

Goal read_email Goal memorize_sender's_name

Goal read_email_body

Goal reply_email(x) Selection rule Select_appropriate_formulation(x)

Goal reply_email_friend

Operator Type (Hi <x>)

…

Goal reply_email_familly

Operator Type (Dear <x>)

…

Loop

Goal: Logout

Mental operations

Perceived_item: John

Visual buffer

(John, relation, friend)

Long term memory

(Jack, relation, family)

If Perceived_item = XAnd (X, relation, friend)

Then Process goal reply_email_friend

Selection rule

Reply_email_friendReply_email_familymemorize_sender's_name

Goals

(email, name, John)

How To Use GOMS

1. Analyze hierarchical structure of a task

a. coarse analysis focuses more on the cognitive structure of a task

b. fine analysis focuses more on the structure imposed by the specific interface design

2. Analyze alternative methods

3. Assign operators to base level goals

4. Assign times to operators

5. Sum the operator times

Operator Times

Press key on keyboard 280 ms

Use mouse to point to object on screen 1,500 ms

Move hand to pointing device 300 ms

Move eyes to location on screen 230 ms

Retrieve item from memory 1,200 ms

Learn a single step in a procedure 25,000 ms

Select among methods 1,200 ms

More available in ABCS, GOMSL and CM&N

Summary

• A method to describe tasks and how a user performs those tasks with a specific design– bridges task analysis with a specific interface design

– error-free, goal-directed, and rational behavior

• Views humans as information processors– small number of cognitive, perceptual, and motor operators characterize

user behavior

• To apply GOMS:– analyze task to identify user goals (hierarchical)

– identify operators to achieve goals

– sum operator times to predict performance


Using GOMS for text editing [1]

Operators Mental primitives for flow of control:

Accomplish the goal of <goal description>

Report goal accomplished

Decision: if<operator> then<operator> else<operator>

Goto step <number>

Memory stage and retrieval Recall that <working memory object>

Retain that <working memory object>

Forget that <working memory object>

Retrieve LTM that <long-term-memory object>

Primitive external operators Move mouse

Press key <key name>

Type in <string of characters>

Move-cursor to <target coordinates>


Errors [1]

Errors: deviations from intentional behavior that is

either skill, rule or knowledge based.

Classification of errors based on behavior type:

Skill based behavior: automatic behavior that is

predefined and requires minimal cognitive resources.

Rule based behavior: controlled behavior that relies

on predefined rules of behavior that are contingent on

particular situation encountered.

Knowledge based behavior: highly controlled

behavior that requires assessment and generation of

new rules of behavior, and is demanding of cognitive

resources.

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Unidad IV Ingenier a Cognitiva