Usability of Interactive Systems Shneiderman and Plaisant, Chapter 1 Preece, Rogers, and Sharp, Chapter 1 (some slides at

Usability of Interactive Systems

Shneiderman and Plaisant, Chapter 1Preece, Rogers, and Sharp, Chapter 1

(some slides at http://wps.aw.com/aw_shneider_dtui_4/ and AW, Preece et al.)

http://wps.aw.com/aw_shneider_dtui_4/

Familiar Systems …Recall from last time

• What is the below?– Right, a computer

• Many (essentially all) courses concerned with, e.g., algorithms, architecture, operating systems, …

– How many courses have you had concerned with these?

Familiar Systems …

• What is the below?– Right, a human

• Not so many courses in your curriculum talk about

• However, without humans there would be no computer science!


• So, the subject(s) of this course – human computer interaction– Computer system, human, software, hardware, programming, models, …

• And – most importantly, their interaction– Human-Computer Interaction: HCI


• So, the subject(s) of this course – design for it

• And – interaction– Human-Computer Interaction: HCI


• So, the subject(s) of this course – human computer interaction– Computer system, human, software, hardware, programming, models, …

• And – interaction– Human-Computer Interaction: HCI

• Even learn some things about the human– Cognition, performance, …

Usability

• How well can the interface be used – it’s just that simple• How usable is the interface

• … and now, the really big picture …

Well, “…it could be better …”Interface Hall of Shame!

• Click & Print Certificates– "Style Buddy“

• “Minor” obvious problems:– Instructions in title bar, – Right-aligned, vertically-

oriented instructions, – Cancel button before OK

button– Reference to an "OKAY"

button– Use of all capital letters– “sickly green color”– etc.

• And major problem …

Isys Information Architects – Interface Hall of Shamehttp://homepage.mac.com/bradster/iarchitect/controls.htm

“…could be better …”

• And major problem …

• In fact are 9 styles of awards

• Must use horizontal slider to see

– Sequential search

• Sure, can make it better


“Better …”

• Range of styles evident through list box

– Which also provides selection style more familiar to user

– “inconsistency” fixed

• “Minor” things fixed, as well– (except color)

• Clearly, more “usable”– Will explore in detail what that means

• Things “obvious” here– Will spend a fair amount of time

learning “principles” for systematically evaluating


“The interface is the system.”

“The interface is the system.”

• Interface provides/conveys the only view of the “underlying” system

– Provides:• Model of task, system capabilities … more later

– “Mental model” of the system – more later

• User interface strongly affects perception of software• Recall, example of UTPA registration system

– Usable software sells better– Unusable web sites are abandoned

• Perception is sometimes superficial– Users blame themselves for UI failings

• … and this is a “deep”, or ethical, problem

– People who make buying decisions are not always end-users

Interfaces – Should and Must Do Right

• Always should have “good” interfaces– Computing time (power) is getting cheaper– Users’ time isn’t– Ratio discussed last time

• Sometimes must have “good” interfaces

• Disasters happen (notes)– Therac-25 radiation therapy machine– Operator had to ”know” to wait

• Vs. have as part of ui

• ACM Code of Ethics

Leveson, N. (1995). Appendix - Medical Devices: The Therac-25http://sunnyday.mit.edu/papers/therac.pdf

In fact, User Interfaces are Hard to Design

• Software designers (let alone coders!) are not the user– As we’ve discussed– Most software engineering is about communicating with other programmers

• SE about says to systematically design a software system– UI is about communicating with users

• “The user is always right”– E.g., consistent problems are the system’s fault– Providing “tools for tasks” is the ultimate goal – the tasks of the user

• …except when the user is not right– Users aren’t designers– Can be reasons to

• “guide” the user, e.g., to use all functionality• Constrain the user, e.g., Therac-25 example … “takes so long to …”

Usability

• Is it a “good” interface?– In what ways?

• Usability: – How well users can use the system’s functionality

• Dimensions of usability (quick look):– Learnability: is it easy to learn?– Efficiency: once learned, is it fast to use?– Memorability: is it easy to remember what you learned?– Errors: are errors few and recoverable?– Satisfaction: is it enjoyable to use?

Usability Dimensions Vary In Importance

• So, what are the elements of usability?

• … It depends on the user– Novice users need learnability– Infrequent users need memorability– Experts need efficiency

• But no user is uniformly novice or expert– Domain experience– Application experience– Feature experience– …

Usability Is Only One Attribute of a System

• In developing large systems, development process entails a (often large) team

– Often competing goals, cost, efficiency, portability, …

• Software designers have a lot to worry about:– Functionality – Usability– Performance – Size– Cost – Reliability– Security – Standards

• Many design decisions involve tradeoffs among different attributes– Which is the essence of the design process

Usability Engineering Is a Process

• … an iterative process

• Design

• Implement

• Evaluate

• Will later look at the “spiral” model of software engineering, which systematically incorporates iteration and change

Design

Evaluate Implement


• Design

• Task analysis– “Know thy user”– “Know thy domain”

• Design principles– Overarching– Much more later

• Design guidelines– Avoid obvious mistakes– May be vague or contradictory

Design

Evaluate Implement


• Implement

• Prototyping– Cheap, throw-away

implementations– Low-fidelity: paper, Wizard of

Oz– Medium-fidelity: HTML, Visual

Basic

• GUI implementation techniques– Input/output models– Toolkits– UI builders

Design

Evaluate Implement


• Evaluate

• Evaluation tests prototypes, using …

• Expert evaluation– Heuristics and walk-throughs

• Predictive evaluation– Testing against an engineering

model (simulated user)

• Empirical evaluation– Watching users do it

Design

Evaluate Implement


• Often called “user centered design

• Cycle of design, implement, evaluate firmly places user as a “design factor”

Design

Evaluate Implement

Now, examples, details …

Examples of Bad Design … and Why

– Elevator controls and labels on the bottom row all look the same, so it is easy to push a label by mistake instead of a control button

– People do not make same mistake for the labels and buttons on the top row. Why not?

From: www.baddesigns.com

Why is this vending machine so bad?

• Need to push button first to activate reader

• Normally insert bill first before making selection

• Contravenes well known convention


Principles of Design – Big Picture(Preece et al.)

• Design … of pretty much everything – computers, doors, ... – Interaction design ... a broader view the “just” hci design– Broadly characterized, information (technology) can be embedded in any object

• …and enumeration (of elements and techniques) helps ... – Techniques of design

• What to design - need to take into account:• Who the users are• What activities are being carried out• Where the interaction is taking place• What goal of interactions is

• Need to optimize interactions users have with a product such that they match the users activities and needs

Principles of Design – Big Picture(Preece et al.)

• … of pretty much everything – computers, doors, ... – Interaction design– And information technology can be embedded in any object

(recall last week and supplementary reading)

• Understanding users’ needs– Need to take into account what people are good and bad at– Consider what might help people in way they currently do things– Listen to what people want and get them involved– Use tried and tested user-based methods

• Human-computer interaction design is more narrow ...

What is Human Computer Interaction?

• Human-computer interaction (HCI) is:

– “concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them” (ACM SIGCHI, 1992, p.6)

What is Human Computer Interaction?

• Human-computer interaction (HCI) is:

– An “interdisciplinary design science”, Shneiderman

• Began by “combining data-gathering methods and intellectual frameworks of experimental psychology with the powerful and widely used tools developed from computer science…”

• … “contributions accrued from educational and industrial psychologists, industrial and graphic designers, technical writers, experts in human factors or ergonomics, information architects, and adventuresome anthropologists and sociologists.”

What is Interaction Design?• The more general question …

• Interaction design (ID) is (Winograd, 1997):

– “the design of spaces for human communication and interaction”




• What does this mean?

– An architect is to a (civil) engineer, as An interaction designer is to a software engineer




– An architect is to a (civil) engineer, as An interaction designer is to a software engineer

• Increasingly, more application areas, more technologies and more issues to consider when designing “interfaces”

• ID is highly interdisciplinary, as will see …

• Interaction design is more general than HCI

• HCI is one contributor to ID

Relationships of ID, HCI and Other Fields, 1

• Again, interaction design is the broadest perspective

• Academic disciplines contributing to ID:

– Psychology– Social Sciences– Computing Sciences– Engineering– Ergonomics– Informatics

• Design practices contributing to ID:

– Graphic design– Product design– Artist-design– Industrial design– Film industry

Interdisciplinary fields (e.g HCI, CSCW)

Design practices(e.g. graphic design, product design)

Academic disciplines(e.g. computer science,psychology)

Interaction Design

Relationships of ID, HCI and Other Fields, 2

• Interdisciplinary fields that ‘do’ interaction design:

– Human Computer Interaction– Human Factors– Cognitive Engineering– Cognitive Ergonomics– Computer Supported Co-operative

Work (CSCW)– Information Systems

• AND there are challenges of interdisciplinary work

– The more people involved in doing interaction design the more ideas and designs generated…but…

– The more difficult it can be to communicate and progress forwards the designs being created

Interdisciplinary fields (e.g HCI, CSCW)

Design practices(e.g. graphic design, product design)

Academic disciplines(e.g. computer science,psychology)

Interaction Design

Professionals in HCI and IDSome terms used

• Interaction designers – Involved in the design of all the interactive aspects of a product

• User interface architect– Term often used for member of software team for interface issues

• Usability engineers – Focus on evaluating products, using usability methods and principles

• Web designers – Develop and create the visual design of websites, such as layouts

• Though used more broadly these days … “anyone who creates a web site”– But, then, a coder is not a software engineer

• Information architects – How to plan and structure knowledge rich interactive products

• “User experience designers” – Do all above, and may carry out studies to inform design of products

Interaction Design (and Software Engineering)

• As seen earlier … general process for software design (more later)

– Identify needs and establish requirements

– Develop alternative (here, interaction) designs• According to principles and/or guidelines

– Build interactive prototypes that can be communicated and assessed• Design, especially user-centered design, is an iterative process

– more later, e.g., “spiral model”, orientation tonight

– Evaluate what is being built throughout the process• Much more on how later to evaluate interaction later

• Core characteristics – of iterative design, user-centered design – said again– Users should be involved throughout development of project– Specific usability and user experience goals need to be identified, clearly documented,

and agreed at beginning of project– Iteration is needed through the core activities

Introduction – Shneiderman, 1

• Again, interdisciplinary design science of Human-Computer Interaction (HCI) combines knowledge and methods associated with different professionals

• Nature of interface design sometimes critical in success

– Success Stories: Google, Apple, Amazon.com, …

– Competition: Netscape vs. Internet Explorer

– Copyright Infringement Suits – • Apple vs. Microsoft (Windows )

– Corporate Takeovers: IBM's seizure of Lotus

– Privacy and Security issues: • identification theft, medical information, viruses, spam, national security

Introduction – Shneiderman, 2

• Critical role of user interface in range of applications– Recall, “the interface is the system”

• Individual User Level – Routine processes: tax return preparation– Decision support: a doctor’s diagnosis and treatment– Education and training: encyclopedias, drill-and-practice exercises, simulations– Leisure: music and sports information

• Communities – and more and more and … true global change– Business use: financial planning, publishing applications– Industries and professions: web resources for journals, and career opportunities– Family use: entertainment and communication– Globalization: language and culture

Trends/Possibilities, from Shneidermanah, the future …

• Display size, micro (phone) to mega (wall)

• Desktop computers may disappear– “only to become ubiquitous, pervasive, and embedded in the surrounding

environment”

• Novel appliances will be – “context-aware, attentive, & perceptive, sensing users’ needs and providing

feedback through displays that glow, hum, change shape, or blow air”

• Advanced mobile devices - portable, wearable, or implanted in skin

• Pervasive technologies that:– Change users’ behavior– Multi-modal or gestural interfaces facilitate use– Affective interfaces that respond to user’s emotional state

Shneiderman Book overview:

• Chapter 1: – Broad overview of hci from practitioner and research perspectives

• Guidelines, principles, and theories– Foundational ideas for design

• Development Processes– Design processes and interface evaluation

• Evaluation– How to assess usability

• Interaction Styles– Menus, dialog boxes, form fillin, command and natural languages, direct manipulation

• Design Issues– “Balancing form and function”, documentation, search and visualization

• Afterword:– Societal and individual impacts of technology

Usability – More Ideas

• Usability requirements

• Goals

• Different kinds of usability

• User experience

• Visibility, feedback, mappings

• Affordances

• Usability measures

• Universal usability

Usability Requirements, 1/2

• “Usability” is not a pretty word, … but idea is– And it is better than “user-friendly” (… for heaven’s sake) – Synonyms for “user-friendly”

• easy to use; accessible; comprehensible; intelligible

• Ultimately, computers, and their interfaces are here to allow / enable / facilitate people doing things they need to or just want to do

– Facilitated by computing/electronic technology– Task (which can be entertainment) and machine– Interface “disappears”

• immersed in the task (or domain) “one with the task”, …

– Task engagement

• These measures are still subjective and vague, so a systematic process is necessary to develop usable systems for specific users in a specific context …

– (next slide)

Usability Requirements, 2/2

• …systematic process is necessary to develop usable systems for specific users in a specific context

• E.g., “U.S. Military Standard for Human Engineering Design Criteria” (1999) states these purposes – which suggest steps toward measurement:

– Achieve required performance by operator, control, and maintenance personnel– Minimize skill and personnel requirements and training time– Achieve required reliability of personnel-equipment/software combinations– Foster design standardization within and among systems

• Usability requires project management and careful attention to requirements analysis and testing for clearly defined objectives

Usability Goals

• In short, goals of increased “usability” of a system are that it is:

– Effective to use

– Efficient to use

– Safe to use

– Has good utility

– Easy to learn

– Easy to remember how to use

• More later …

User Experience and Usability(Preece et al.)

• “User experience”– Encompasses more

then usability• (see innermost for

usability goals)• Detail, next slide

– Also, note Preece’s elements of usability

• In part an affective element of the interface

User Experience

• “User Experience” - goals– Satisfying - Rewarding– Fun - Support creativity– Enjoyable - “emotionally fulfilling”– Entertaining - Helpful– Motivating - Aesthetically pleasing– Motivating - …and more

• Usability and user experience goals …

– How do usability goals differ from user experience goals?

– Are there trade-offs between the two kinds of goals?• e.g., can a product be both fun and safe?

– How easy is it to measure usability versus user experience goals?

Design Principles(Overview Now from ID perspective, HCI and SE perspective later)

• Some (quick) principles for good design (more next class):– Visibility (example next)

• Of interaction elements and all elements, e.g., feedback– Feedback– Constraints– Good mappings

• Recall, elevator– Consistency– … examples to follow

• Design Principles are …– Derived from a mix of

• theory-based knowledge, experience and common-sense– Generalizable abstractions for thinking about different aspects of design

– “The do’s and don’t’s of interaction design”

– What to provide and what not to provide at interface

Visibility - Example

• Control panel for an elevator

• How does it work?

• Push a button for the floor you want?

• Nothing happens - Push any other button?

Still nothing.

• What do you need to do?

• It is not visible as to what to do!

www.baddesigns.com

Visibility

…need to insert room card in slot by buttons to get elevator to work!

How would to make this action more visible?

• Make card reader more obvious• Provide an auditory message that says

what to do (which language?)• Provide a big label next to the card

reader that flashes when someone enters

• Make relevant parts visible• Make what has to be done obvious

Feedback

• Sending information back to the user about what has been done

• Includes sound, highlighting, animation and combinations of these

– e.g. when screen button clicked on provides sound or red highlight feedback:

“ccclichhk”

Constraints

• Restricting the possible actions that can be performed

• Helps prevent user from selecting incorrect options

• Three main types (Norman, 1999)– Physical

• Refer to the way physical objects restrict the movement of things– E.g. only one way you can insert a key into a lock

• How many ways can you insert a CD or DVD disk into a computer?• How physically constraining is this action?• How does it differ from the insertion of a usb drive into a computer?

– Logical• Exploits people’s everyday common sense reasoning about the way the

world works• An example is they logical relationship between physical layout of a device

and the way it works as the next slide illustrates

– Cultural • Learned, arbitrary signs

Logical or ambiguous design?

• Where do you plug the mouse?

• Where do you plug the keyboard?

• top or bottom connector?

• Do the color coded icons help?


How to design more logically

- A. provides direct adjacent mapping between icon and connector

- B. provides color coding to associate the connectors with the labels


Cultural constraints

• Learned arbitrary conventions like red triangles for warning

• Can be universal or culturally specific

Which universal, which culturally-specific?

• .

Mapping

• Relationship between controls and their movements and the results in the world

• Why is this a poor mapping of vcr control buttons (rewind, play, fast forward, fast rewind)?

Mapping

• Why is this a better mapping?

• The control buttons are mapped better onto the sequence of actions of fast rewind, rewind, play and fast forward

Mapping

– Which controls go with which rings (burners)?

A B C D

Why is this a better design?

Consistency

• Design interfaces to have similar operations and use similar elements for similar task

• For example:– always use ctrl key plus first initial of the command for an operation – ctrl+C,

ctrl+S, ctrl+O

• Main benefit is consistent interfaces are easier to learn and use

• When consistency breaks down– What happens if there is more than one command starting with the same

letter?• e.g. save, spelling, select, style

– Have to find other initials or combinations of keys, thereby breaking the consistency rule

• E.g. ctrl+S, ctrl+Sp, ctrl+shift+L

– Increases learning burden on user, making them more prone to errors

Internal and External Consistency

• Internal consistency – Designing operations to behave the same within an application– Difficult to achieve with complex interfaces

• External consistency – Designing operations, interfaces, etc., to be the same across applications and

devices– Very rarely the case, based on different designer’s preference– But, in computing environment, guidelines can influence

External Inconsistency …

• Keypad numbers layout

1 2 3

4 5 6

7 8 9

7 8 9

1 2 3

4 5 6

0 0

(a) phones, remote controls (b) calculators, computer keypads

Affordances: “To give a clue”(short version)

Affordances: “To give a clue” (short version)

• From Gibson’s theory of perception

• Refers to an attribute of an object that allows people to know how to use it

– a mouse button “invites” pushing– a door handle “affords” pulling– … sort of– used somewhat as a metaphor, vs. rigorous application of a theory of perception

• We’ll have a look to see “cross-disciplinary” fertilization

• Norman used term to discuss design of everyday objects

• Much popularised in interaction design to discuss how to design interface objects

– scrollbars to “afford” moving up and down, – icons to “afford” clicking on

fyi - Gibson’s Affordance Theory, 1

• Perception theorist, J. J. Gibson– Ecological optics, affordances, direct perception, …

• Orienting assumption: – we perceive to operate on the environment

– Perception is “designed” (or evolved) for action, so we perceive• Surfaces for walking, handles for pulling, space for navigating, tools for

using, …

• Perceivable possibilities for action, he called affordances


• Perceivable possibilities for action, Gibson called affordances

• Claimed affordances are perceived directly and immediately (vs. piecing together atomic elements)

– Useful notion for interaction, as goal often decision making (broadly construed)

• This “top down” view contrasts fundamentally with a “bottom up” account of perception

– E.g., perceive (directly) surfaces for walking vs. points of light which come together to form a line, which …

– Though certainly directed arcs can convey same meaning – it is the indication of “operability” that is important


• Perceivable possibilities for action … affordances– Perceived directly and immediately – “Top down” view contrasts fundamentally with a “bottom up” account of

perception

• For interfaces: – To create a good interface, must create it with appropriate affordances to make

user’s task easy– E.g., when object selected, make handles (or whatever) appear that the object

might be moved (or something)– Below demonstrates:

• Hands appear to indicate possible operations when object selected• Though certainly directed arcs can convey same meaning – it is the

indication of “operability” that is important

fyi - Gibson’s Affordance Theory, But …

• Alternatives to Gibsonian view perception as active (vs. direct) process

• E.g., perceptual hypotheses are confirmed or disconfirmed based on sensory evidence

• Certain things about environment are deduced based on sensory evidence

• Problems with Gibson’s account for developing theory of interaction…

fyi - Gibson’s Affordance Theory, But …

• Though perception of (real) environment is direct, perception of computer presented environment not

– Many layers of processing between display image and perception, data may in fact be abstract, etc.

• There are no clear physical affordances in any graphical user interface

– A screen button just is fundamentally different than a sidewalk– “the screen button affords pressing” is a stretch

• Heck, it’s just an interface object that has been mapped arbitrarily to selecting • And we’ve clearly learned that mapping

• Ignoring visual mechanisms seems inappropriate• E.g., much to be learned about color perception using knowledge of neurons,

psychophysics, etc.

• Yet, idea of affordances seems useful in suggesting, at least metaphorically, strategies for tasks and elements of understanding

What Affordance offers Interaction Design

• In fact …– Interfaces are virtual and do not have affordances like physical objects

• Norman argues it does not make sense to talk about interfaces in terms of ‘real’ affordances

• Instead, interfaces are better conceptualised as ‘perceived’ affordances

– Learned conventions of arbitrary mappings between action and effect at the interface

– And some mappings are better than others …– (sensory vs. arbitrary symbols)

Examples of Affordances

• Physical affordances: – How do the following physical objects afford? – Are they obvious?

Examples of Affordances

– Virtual affordances• How do the following screen objects afford?• What if you were a novice user?• Would you know what to do with them?

Key Points about Interaction Design(summary)

• ID is concerned with designing interactive products to support people in their everyday and working lives

• ID is multidisciplinary– Involves many inputs from wide-reaching disciplines and fields

• ID is big business

• ID involves taking into account a number of interdependent factors including context of use, type of task and kind of user

• Need to strive for usability and user experience goals

• Design and usability principles are useful heuristics for analyzing and evaluating interactive products

Another Perspective …

• The hci (vs. id) perspective

Another Perspective …… the Human Computer Interaction Perspective

• Shneiderman’s text is more oriented toward the narrower domain of human-computer system design– Vs. “all things”

• As you begin to “think like a designer”…, examine and use both orientations

Goals for Requirements Analysis -A Software Engineering Perspective

• Saw example of “general” interaction design principles

• Now, Shneiderman’s HCI perspective

• Again, familiar from software engineering, requirements analysis stage

• Goals– 1. Ascertain the users’ (and client’s) needs

– 2. Ensure reliability

– 3. Promote standardization, integration, consistency, and portability

– 4. Complete projects on time and within budget

Goals for Requirements Analysis -A Software Engineering Perspective

1. Ascertain the user’s needs– Determine what tasks and subtasks must be carried out

• Clearly, completely and unambiguously– Common tasks are easy to identify

• Also, Include tasks which are only performed occasionally.. – Functionality must match need or else users will reject or underutilize the

product

2. Ensure reliability – Actions must function as specified – Database data displayed must reflect the actual database– Appease the user's sense of mistrust – System should be available as often as possible– System must not introduce errors – Ensure user's privacy and data security by protecting against

• Unwarranted access, destruction of data, and malicious tampering

Goals for Requirements Analysis Software Engineering Perspective

3. Promote standardization, integration, consistency, and portability – Standardization:

• use pre-existing industry standards where they exist to aid learning and avoid errors (e.g. the W3C and ISO standards)

– Integration: • product should be able to run across different software tools and packages (e.g.

Unix)

– Consistency: • compatibility across different product versions

• compatibility with related paper and other non-computer based systems

• use common action sequences, terms, units, colors, etc. within the program

– Portability: • allow for user to convert data across multiple software and hardware environments

4. Complete projects on time and within budget– Late or over budget products can create serious pressure within a company

and potentially mean dissatisfied customers and loss of business to competitors

Usability Measures – 5 Often Used

• Measurement in usability a key notion

• Define target user community and class of tasks associated with interface

• Communities evolve and change

– e.g., the interface to information services for the U.S. Library of Congress

• 5 “human factors” (usability measures) central to evaluation: • Detail, next slide

– Time to learn– Speed of performance– Rate of errors by users– Retention over time– Subjective satisfaction

Usability Measures – 5 Often UsedMetrics for each

• Time to learn– How long does it take for typical members of the community to learn relevant

task?

• Speed of performance– How long does it take to perform relevant benchmarks?

• Rate of errors by users– How many and what kinds of errors are made during benchmark tasks?

• Retention over time– Frequency of use and ease of learning help make for better user retention

• Subjective satisfaction– Do users like it?– User feedback via interviews, free-form comments and satisfaction scales

Usability Measures Design Trade-offs

• And, design is about trade-offs– E.g., time to learn vs. speed of performance – gui vs. command line, rm *.*

• Trade-offs in design options frequently occur– Changes to interface in a new version may create consistency problems with

previous version, – But, changes may improve interface in other ways or introduce new needed

functionality.

• Design alternatives can be evaluated by designers and users via mockups or prototypes

– Basic tradeoff is getting feedback early and perhaps less expensively in development process versus having a more authentic interface evaluated

• Also, all of below can change:– E.g., with use of product, e.g., browsers, word processors, games, …– Define target user community and class of tasks associated with interface – Communities evolve and change

Usability – Types of Systems 1/5Challenges of Design

• Many interfaces are poorly designed and this is true across domains– Role of “well designed” (by previous criteria) interfaces recognized

• Different system types have different needs– E.g., life-critical, industrial and commercial, office and home, exploratory, social-

technical, …

• Following provides a quick look at the challenge of interface design– A complex design process, involving tradeoffs, in domains that are themselves

evolving

1. Life-critical systems

2. Industrial and commercial uses

3. Office, home, and entertainment applications

4. Exploratory, creative, and cooperative systems

5. Social-technical systems


1. Life-critical systems • Air traffic control, nuclear reactors, power utilities, police & fire dispatch systems

– High costs, reliability and effectiveness are expected

– Lengthy training periods are acceptable despite financial cost • provide error-free performance and avoid the low frequency but high cost errors

– Subject satisfaction is less an issue due to well motivated users


1. Life-critical systems • Air traffic control, nuclear reactors, power utilities, police & fire dispatch systems

– High costs, reliability and effectiveness are expected

– Lengthy training periods are acceptable despite financial cost • provide error-free performance and avoid the low frequency but high cost errors

– Subject satisfaction is less an issue due to well motivated users

2. Industrial and commercial uses • Banking, insurance, order entry, inventory management, reservation, billing, and point-of-

sales systems

– Ease of learning is important to reduce training costs

– Speed and error rates are relative to cost

– Speed of performance is important because of the number of transactions

– Subjective satisfaction is fairly important to limit operator burnout


3. Office, home, and entertainment applications • Word processing, electronic mail, computer conferencing, and video game systems,

educational packages, search engines, mobile device, etc.

– Ease of learning, low error rates, and subjective satisfaction are paramount due to use is often discretionary and competition among available systems high

– Infrequent use of some applications • Means interfaces must be intuitive and easy to use online help is important

– Choosing functionality is difficult• Population has a wide range of both novice and expert users

– Competition causes the need for low cost


4. Exploratory, creative, and cooperative systems • Web browsing, search engines, artist toolkits, architectural design, software

development, music composition, and scientific modeling systems

– Includes collaborative work

– Benchmarks are hard to describe for exploratory tasks and device users

– And very nature of exploration is hard to define and describe

– With these applications, the computer should "vanish" so that the user can be absorbed in their task domain


5. Social-technical systems

– Complex systems that involve many people over long time periods• Voting, health support, identity verification, crime reporting

– Trust, privacy, responsibility, and security are issues

– Verifiable sources and status feedback are important

– Ease of learning for novices and feedback to build trust

– Administrators need tools to detect unusual patterns of usage

Universal Usability

Universal Usability

• Shneiderman an early champion

• “Universal usability” is about design, and its tradeoffs

– “Accommodating diversity” is simply recognizing fact of differences– Sometimes with unanticipated benefits

• And, the more who can use it, the more that will buy it!

• In summary…, there are variations in:– Physical abilities and physical workplaces

– Cognitive and perceptual abilities

– Personality differences

– Cultural and international diversity

– Users with disabilities

– Elderly users

– Children

Universal Usability: Physical Abilities and Physical Workplaces

• Basic data about human dimensions from research in anthropometry

• There is no average user– Either compromises must be made or multiple versions of a system must be created

• Physical measurement of human dimensions are not enough– Take into account dynamic measures such as reach, strength or speed

• E.g., screen-brightness preferences vary substantially– Designers customarily allow user control

• Account for variances of the user population's sense perception– Vision: depth, contrast, color blindness, and motion sensitivity – Touch: keyboard and touchscreen sensitivity – Hearing: audio clues must be distinct

• Workplace design can both help and hinder work performance

Universal Usability: Cognitive and Perceptual Abilities, 1

• The human ability to interpret sensory input rapidly and to initiate complex actions makes modern computer systems possible

• Ergonomics Abstracts (EA) classification of human cognitive processes:– (more later in semester …)

– Long-term and semantic memory

– Short-term and working memory

– Problem solving and reasoning

– Decision making and risk assessment

– Language communication and comprehension

– Search, imagery, and sensory memory

– Learning, skill development, knowledge acquisition and concept attainment

Universal Usability: Cognitive and Perceptual Abilities, 2

• EA suggests this set of factors affecting perceptual and motor performance:

– Arousal and vigilance– Fatigue and sleep deprivation– Perceptual (mental) load– Knowledge of results and feedback– Monotony and boredom– Sensory deprivation– Nutrition and diet– Fear, anxiety, mood, and emotion– Drugs, smoking, and alcohol– Physiological rhythms

• But … in any application, background experience and knowledge in the task domain and the interface domain play key roles in learning and performance

Universal Usability: Personality Differences

• Personality makes a difference, – e.g., some folks just don’t like (or at least love) computers!, gender differences, …

“people are different” - inherently

• There is no set taxonomy for identifying user personality types • Designers must be aware that populations are subdivided and that these

subdivisions have various responses to different stimuli

• E.g., Myers-Briggs Type Indicator – after Jung’s theories of personality

– extroversion vs. introversion • Focus on external stimuli vs. inner ideas

– sensing vs. intuition • Routine tasks, precise work, applying known skill vs. solving new problems, discovery, not time for precision

– perceptive vs. judging • Learn new situations, but not make decisions vs. careful plan and its execution regardless of new inform.

– feeling vs. thinking • Aware of other’s feels, please others, relate to people vs. unemotional, often impersonal, logical order

Universal Usability: Cultural and International Differences

• Cultural and international diversity

• Some internationalization issues …– Differences exist, e.g., buildings vs. people on home web pages– Characters, numerals, special characters, and diacriticals – Left-to-right versus right-to-left versus vertical input and reading – Date and time formats – Numeric and currency formats – Weights and measures – Telephone numbers and addresses – Names and titles (Mr., Ms., Mme.) – Social-security, national identification, and passport numbers – Capitalization and punctuation – Sorting sequences – Icons, buttons, colors – Pluralization, grammar, spelling – Etiquette, policies, tone, formality, metaphors

Universal Usability: Users with Disabilities, “Older” Users, Children

• Users with disabilities– Designers must plan early to accommodate users with disabilities – Early planning is more cost efficient than adding on later – Businesses must comply with the "Americans With Disabilities" Act for some

applications – Consider, e.g., vision impairment, hearing, …, even color blindness– Nice overlap with older user needs

• “Older” Users– A few years ago, “literacy” a challenge – problem taking care of itself– Including “older” is fairly easy

• Allow for variability within applications via settings for sound, color, brightness, font sizes, etc.

• Children– Need for protection – privacy, malevolence– Elements of development and education– Action oriented

Universal Usability:… and finally …

• From ACM code of ethics:

– “In a fair society, all individuals would have equal opportunity to participate in, or benefit from, the use of computer resources regardless of race, sex, religion, age, disability, national origin or other such similar factors.”

Universal Usability:… and finally …

• From ACM code of ethics:

– “In a fair society, all individuals would have equal opportunity to participate in, or benefit from, the use of computer resources regardless of race, sex, religion, age, disability, national origin or other such similar factors.”

• From Shneiderman’s CACM article – front matter:– “I feel … an ardent desire to see knowledge so disseminated

through the mass of mankind that it may … reach even the extremes of society: beggars and kings.”

• Thomas Jefferson

• Reply to American Philosophical Society, 1808

Goals for HCI Profession

Goals for HCI Profession

• Science vs. intuition in interface design …– “There are places for both…”

• But, actually, what is intuition … ?– Does it come from “above”, … or does it come from training and/or observation…?

• Three goals for HCI (Shneiderman):

– Influencing academic and industrial researchers

– Providing tools, techniques, and knowledge for commercial designer

– Raising the computer consciousness of the general public

Goal: Influencing Academic and Industrial Researchers

• Apply the “scientific method for interface design (according to Shneiderman)”:

– Understanding of a practical problem and related theory– Lucid statement of a testable hypothesis– Manipulation of a small number of independent variables– Measurement of specific dependent variables– Careful selection and assignment of subjects– Control for bias in subjects, procedures, and materials– Application of statistical tests– Interpretation of results, refinement of theory, and guidance for experimenters

• Potential research topics– Reducing anxiety and fear of computer usage – Graceful Evolution – Social media participation– Input devices – Online help – Information exploration

Goals for HCI profession, 2/2

• Providing tools, techniques, and knowledge for system implementers

– Rapid prototyping is easy when using contemporary tools – Use general or self-determined guideline documents written for specific

audiences – To refine systems, use feedback from individual or groups of users

• Raising the computer consciousness of the general public– Many novice users are “unenthusiastice” due to experience with poor

product design, – Good designs help novices by being clear, competent, and nonthreatening

End

Documents

Usability of Interactive Systems Shneiderman and Plaisant, Chapter 1 Preece, Rogers, and Sharp, Chapter 1 (some slides at