May 1, 2007Mohamad Eid Introduction to Human Computer Interaction Chapter 1

May 1, 2007 Mohamad Eid

Introduction to Human Computer Interaction

Chapter 1


Outline

1. Human Computer Interaction: definition2. Why study user interface design?3. History4. Goals of HCI5. Five key ideas in HCI6. Optical Illusions 7. Understanding users8. User productivity and usability9. Disciplines contributing to HCI10. HCI engineering as a branch of software engineering11. User interface malfunctions12. Case studies in user interface malfunction13. Key points to review


Definition

The study of people and computing and the way they influence each other

A set of processes, dialogues, and actions through which a human user employs and interacts with a computer

A discipline concerned with the design, evaluation and implementation of interactive computing systems for human use with the study of major phenomena surrounding them


Human-Computer Interaction (HCI)

Human the end-user of a program the others in the organization

Computer the machine the program runs on

Interaction the user tells the computer what they

want the computer communicates results

The System

The User

Input Output


Why Study User Interface Design?

75% or more of development effort can go into the user interface 40% to 70% is typical User interface specialists are needed Everybody needs to know the basics

User interface software is becoming more complex Complexity increase is faster than other aspects of systems Graphical user interfaces have provided the biggest jump in

complexity Applications tend to grow to fill available computing resources

There are direct financial benefits from improved user interfaces


Financial benefits & Costs of improved user interfaces

Increased user productivity Direct financial savings

Increased revenues from sales The system is more attractive and customer satisfaction is higher

Decreased training and support costs The system is more intuitive

Decreased maintenance cost The system does what user wants Much maintenance involves fixing UI problems Pay a little during development, or pay a lot after

application/product release! But

Staff must be trained in user interface analysis and design Users must participate UI design tools are needed.

The benefits almost always outweigh the costs


History

Early days of computing: Computers cost more than people Computers had little functionality

The UI was unimportant Early 1970s

Field of ‘Man Machine Interface’ (MMI) born. Term changed gradually to ‘User Interface’ (UI) Ideas for first ‘Graphical User Interface’ (GUI)

Dynabook at Xerox Late 1970s and 1980s

Products were called ‘user friendly’ No science in this: Just a market buzzword First real GUI’s developed

Xerox Star --> Smalltalk and Macintosh


History (Cont’d)

1980s Term ‘Human-Computer Interaction’ (HCI or CHI) came into

use wider scope than UI (help, work practices etc.)

MS-Windows, X-Windows follow the Mac Intense research into HCI

1990s and early 2000s Virtual reality, speech and handwriting I/O, Soundblaster

Good BUT also Bad UI’s continue to be developed!!!


Goals of HCI

Improve productivity and reduce costs through: Safety:

Does the system prevent danger? Functionality:

How many things can the system do? Efficiency:

How few resources does it take to get a task done? Usability :

How easy to learn and use is the system?

BUT High functionality (many ways of doing the same thing) can

actually reduce usability By causing confusion


Five Key Ideas in HCI Visibility

The UI should help the user always understand... The current state of the system What operations can be done

E.g. When you position the cursor over a point on the screen, it should be

clear what would happen if you clicked the mouse Feedback

When anything changes it should be made visible When you delete a file, the system should not just say ‘ready’

Goal A state the user wants to reach

to be talking with somebody on the phone to have saved a file


Five Key Ideas in HCI (Cont’d)

Affordance The set of operations and procedures that can be done to an object ‘Perceived affordance’ is what typical users think can be done to an

object Should a door be pulled or pushed? What does this icon mean?

To improve visibility/feedback we need to: Choose objects with good perceived affordance Design the UI to generate better perceived affordance

Task An action the user wants to do

to call somebody to save the file

Goals beget tasks, tasks beget goals.


Optical Illusions


Understanding Users

“Dual Processor" Theory: Every interactive system is a distributed system

running on two processors:

User interface design specifies/constrains both:• User behavior

• System behavior

user

interface

Computer System

Human User


Understanding Users (Cont’d)

Users can be categorized: By class

Determined by the pattern of use: e.g., manager, salesperson, shipper, client

By personality type Shy or reticent Inarticulate Disinterested or defensive Intimidated Involved designer!

By ability Physical disability

--> innovative I/O may be needed Colorblind

--> don’t use colors as the only means of conveying information Dyslexia or other cognitive glitches

--> watch out for left vs. right! Illiteracy

--> icons may be needed Computer illiteracy Ignorance of domain / learner


User Productivity & Usability

User productivity =Functionality (what the computer can do)

*Usability (what people can do with the computer)

If either of these is zero, the system is useless

Factors Influencing User Productivity Kind and number of tasks Characteristics of users (ability, experience etc.) Work environment (distractions etc.) Training and documentation Functionality and usability of available software and hardware


A Model of Usability Factors

usability

enjoyability satisfaction

acceptability

ergonomics

primary functionality

efficiency of use

extensibility/customizationlearnability

ease of usefamiliarity

fit to task

fit to user

cognitive load

error handling


Disciplines Contributing to HCI

Cognitive psychology Capabilities and limitations of human senses and thought processes

Ergonomics Hardware and software efficiency of use and safety

Linguistics Syntax and semantics of commands Speech I/O

Artificial intelligence Speech I/O Intelligent ‘guessing’ what the user wants to do Knowledge representations of users and tasks

Sociology and social psychology Assisting people to work in groups with software Ensuring software works in different cultures

Engineering and industrial design Disciplined measurement-based approaches Esthetics Storyboarding etc.


Human Cognitive system

Perception and representation

Some displays can be hard to interpret Blue foreground Optical illusions Contrast in color but not brightness Too many colors

There are two ways to use graphics: For modeling

direct images of concepts For coding

representing underlying ideas, e.g., displaying quantitative data


Bad User Interface


Human Cognitive system (Cont’d)

Attention limitations

People can be readily distracted Provide cues about what to focus on

People get lost in complexity Structure information so it is easy to browse through

not too many items not too few items grouped logically

People multitask Make the ‘state’ clear so users can jump backwards and forwards

Some mental processes are automatic, or become so (contrasted with controlled processes) These processes are very hard to unlearn


Human Cognitive system (Cont’d)

Memory limitations

Short term memory can contain 7±2 ‘chunks’ Avoid situations where users have to remember more than this Logically group things so users can chunk them

The more meaningful, the more easily remembered (familiarity, imagery and consistency contribute to meaningfulness) Use effective names and icons (even) animated ones Combine icons with words Icons can be analogies, examples or abstract, but not arbitrary Watch out for cultural differences (e.g. washroom symbols)

People can more easily recognize than recall Use menus, icons, quick lookup


A five level conceptual model of the UI

At each level: Design must be done Problems can occur

1. Task Level What is to be done by the user

2. Conceptual Level User’s intended mental model of the system

3. Interaction Style Level Command-driven, menu-driven, direct manipulation, hypermedia Design elements that are repeated throughout the system

4. Interaction Element Level Specific windows, dialogs, commands, menus

5. Physical Element Level Bitmaps, characters, data structures, callbacks


Evolution from plain SW- to usability Eng.

Normal software development (involving the UI) Focuses on physical and interaction elements Waterfall model dominates (sequential), Spiral model Evaluation by functional spec reviews and testing

User interface development Focuses on users and tasks Star model dominates (iterative) Evaluation by continuous user involvement Driven by heuristics and guidelines Integrates psychology etc. Influence on functionality

Usability engineering Driven by engineering objectives Integrates rigorous engineering discipline Drives functionality


A conceptual model of user interface system architecture Why layers?

Simplifies software development and maintenance All layers:

Are developed in parallel Influence each other Included in complete system specifications Evaluated together

Evolution of layers: Functional layer should need to change less often during iterative tuning

of the interface All layers may need to change when business functions change but

hopefully interaction styles should remain similar

Model

Controller

View


Characteristics of Products and Applications

Each kind of application puts different demands on the UI designer Application for internal use vs. product for sale Generic utility vs. task-specific tool Walk-up-and-use vs. skilled usage

Some design challenges: Customizing a generic utility product so that it

becomes a task-specific tool for internal use and vice versa

Converting an application requiring skilled usage to make it a walk-up-and-use application


User Interface Malfunctions

Key idea: “There are no good user interfaces ... just

user interfaces that fit” A truly bad user interface never fits But among the ‘good’ ones, some will suit one task/user;

some with suit another

To maximize fitness, we must minimize the occurrence of ‘malfunctions’ in the context of the expected use of the system


Definitions of malfunction

“A mismatch between what the user wants, needs or expects and what the system

provides”

“A breakdown in usability”

“An obstacle to performing a desired task”

You should know that: Occasional malfunctions are normal Systematic or frequent malfunctions need to be fixed


Related ideas to ‘malfunction’

Error: Identifiable mistake on the part of the designer Defect: A deviation from what the user needs

A malfunction is a usability defect A defect in the smooth functioning of the user/computer

system! Users may not be aware of many malfunctions

the malfunctions may only be located through careful analysis

they may be subtle


Summary

Goals of HCI: Improve safety functionality efficiency usability

Visibility and feedback Affordance and perceived affordance Goal = state; task = action Human/computer as system running on 2 processors Types, classes and abilities of users Productivity = functionality * usability Usability factors

e.g. learnability, fit, acceptability Contributing disciplines

e.g. linguistics, Artificial Intelligence


Summary (Cont’d)

Human cognitive system - Limitations on: perception attention memory

Task analysis vs. functional analysis Star model with evaluation at centre UI levels

task conceptual model interaction style interaction element physical element

Usability engineering Layered approach = Model View Controller Software Design

Pattern Malfunction as a kind of defect (of usability)


متشکرم

谢谢

ありがとう

Documents

May 1, 2007Mohamad Eid Introduction to Human Computer Interaction Chapter 1