May 11, 2007Mohamad Eid Interaction Design Process Chapter 4.
May 1, 2007Mohamad Eid Introduction to Human Computer Interaction Chapter 1.
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Transcript of May 1, 2007Mohamad Eid Introduction to Human Computer Interaction Chapter 1.
May 1, 2007 Mohamad Eid
Introduction to Human Computer Interaction
Chapter 1
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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!!!
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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.
May 1, 2007 Mohamad Eid
Optical Illusions
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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.
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
Bad User Interface
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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
May 1, 2007 Mohamad Eid
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)
May 1, 2007 Mohamad Eid
متشکرم
谢谢
ありがとう