human-ctcomputer-it tiinteraction it d ti &sl tdt iintroduction … · 2012-02-05 ·...

Technische Universität MünchenFachgebiet Verteilte Multimodale InformationsverarbeitungProf. Dr. Matthias Kranz

H C t I t tiHuman-Computer-Interaction -

I t d ti & S l t d T iIntroduction & Selected Topics

Matthias KranzMatthias [email protected]

Guest LectureUniversität Innsbruck

28.01.2011


Introduction Matthias Kranz

Studium der Informatik, Schwerpunkt: Theoretische Informatik

Promotion zum Dr. rer. nat., Forschungsschwerpunkte: „Ubiquitous Computing“ und MCI („HCI“)g g ( )

Wissenschaftlicher Mitarbeiter,Forschungsschwerpunkt: Anwendungen koop. V2X Kommunikationg p g p

Juniorprofessor für Verteilte Multimodale InformationsverarbeitungForschungsschwerpunkte: Pervasive Computing und Ubiquitous Computing, Multimodale Informationsverarbeitung, Verteilte eingebettete Systeme

1/27/2011 2Prof. Dr. Matthias Kranz


Literature (1/3) – Ubiquitous Computing

John Krumm:

Ubiquitous Computing Fundamentals,

Publisher: CRC Press Inc,

Stefan Poslad:

Ubiquitous Computing: Smart

Devices, Environments and Interactions,

ISBN-10: 1420093606,

ISBN-13: 978-1420093605

Publisher: John Wiley & Sons;

ISBN-10: 0470035609,

ISBN-13: 978-047003560

http://www.amazon.dehttp://www.amazon.de



Literature (2/3) – HCI and Design

Mark S. Sanders and Ernest McCormick:

Human Factors in Engineering and Design

Publisher: McGraw Hill,

David Benyon, Phil Turner, Susan Turner:

Designing Interactive Systems

Publisher: Addison-Wesley,

Language: Englisch,

ISBN-10: 007054901X,

ISBN-13: 978-0070549012

Language: Englisch,

ISBN-10: 0321116291,

ISBN-13: 978-0321116291

http://www.amazon.dehttp://www.amazon.de



Literature (3/3) – History & Fun

Michael A. Hiltzik:

Dealers of Ligthning,

Publisher: Harper Paperbacks,

Douglas K. Smith and Robert C. Alexander:

Fumbling the Future

Language: Englisch,

ISBN-10: 0887309895,

ISBN-13: 978-0887309892

Publisher: To Excel/Kaleidoscope Sof,ISBN-10: 1583482660,

ISBN-13: 978-1583482667http://www.amazon.dehttp://www.amazon.de



Overview

Part IPart I

• Introduction and Motivation – Is it hard to create “good” user interfaces?

• Human Computer Interaction – Definition & Context

• Selected Theories and Models: Fitts’s law, Hick’s Law, GOMS

Part IIPart II

• Human Information Processing

• Perception and Gestalt Laws

M D i G id li• Memory Design Guidelines

• Human Errors and Error Avoidance Design Guidelines



Overview

Part IPart I




Part IIPart II







Question...

Is it difficult to create “ordinary” user interfaces?

(And why a VCR is an evil device)



Just a cartoon?

http://dilbert.com/strips/comic/2002-05-11/



os A

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DFKI in Saarbrücken

(Ph

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CS Building in Saarbrücken

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Design of elevator user interfaces...

… missing information ...what is the mapping?

g

relative control?



Both switches belong to the same room, at different entrances.

Design of light switches...

...what is the mapping?



ICE 1 toilet.

Signs and explanations for things that are usually obvious (or should be) are anSigns and explanations for things that are usually obvious (or should be) are an indicator for a potential problem.

The paper box and waste bins are invisible and hard to reachThe paper box and waste bins are invisible and hard to reach.



“Intelligent building monitoring” of a computer science building...

Users are (feel?) no longer in control – the building is “optimized” and autonomously t ll d i d h th b ildi b li it icontrolled – windows open when the building believes it is necessary...

users “deal” with this in their own way...More on the “goodies” in:

htt // b i f /fil d i / di /P blik ti /E B /P j ktb i ht /10 M it i AB1 2 NIZ k dfhttp://www.enob.info/fileadmin/media/Publikationen/EnBau/Projektberichte/10_MonitoringAB1_p2_NIZ_k.pdf



Just replacing existing technology by something else is not enough...

… or do you recall that your “good, old” landline ever broke down, asked for an IP address, or require any configuration?



… list available options

... ask for confirmation in case of potentially harmful behavior

and fail ... and fail



If there are constraints...

... tell the user before he can make his input!



A t f di itAccount for user diversity:

computer science folks might just want to start counting at zero...



All “old” examples? 20.01.2011

offers to save password- offers to save password –but not to save a reminder!

- does not tell you in advance on thelimitationslimitations

- then blames the user for doing it wrong- and, finally, at the same time beingof absolutely no use to the user…of absolutely no use to the user…(ERROR is usually no valid length)

- in case you would not to write descriptive text:pwhy not limit the number of charactersin the input field?

(many, many, many more examples)



The evil VCR

• blinking time (blinking attracts attention)• blinking time (blinking attracts attention)

• always reminding of being not set (telling the user s/he’s not able to set it)

• usually not having to be set – ONLY and ONLY IF the user wants to record

• not setting the time itself – e.g. from the video text (newer models finally did)

• …

1/27/2011 Prof. Dr. Matthias Kranz 19


“Off Screen” HCI?

• Problem for human computer interaction due to incautious design and• Problem for human-computer interaction due to incautious design and development of on-screen user interfaces

ff C ?• “off-screen” HCI?

tangible user interface (physical objects for interaction with digital technology)

smart surfaces (walls, tables, …)

gesture based interaction ( e.g. with MS Kinect/PrimeSense devices)

…



Affordance

• James Gibson 1970: biologically inspired definition of affordance• James Gibson, 1970: biologically inspired definition of affordance

• Affordances are “action possibilities" latent in the environment, objectively measurable and independent of the individual's ability to recognize them, but always in relation to the actor and therefore dependent on their capabilities ”always in relation to the actor and therefore dependent on their capabilities.”

• Affordance design is about perceived and actual properties of an environment/object etc. (Norman)

• properties of affordances are specified in stimulus information – learning may be needed to detect the information

Designing the user interface B Shneiderman and C Plaisant 4th edition Addison Wesley 2004 chapter 7Designing the user interface, B. Shneiderman and C. Plaisant, 4th edition, Addison-Wesley, 2004, chapter 7



Affordance – Example: Doors

• good: color (green: go push red: stop pull)• good: color (green: go - push, red: stop – pull)

• bad: vertical bar: push OR pull both possible

Photos: Matthias KranzPhotos: Matthias Kranz



Affordance – Example: Doors

• http://www infovis net/printMag php?num 72&lang 2• http://www.infovis.net/printMag.php?num=72&lang=2

Figure 1: A door with a metallic plate makes you to perceive that the door is meant to be pushed

Figure 2: In this case the handle of the door let us expect that we have to turn it in order to open

Figure 3: In this door the handle clearly induces us to pull it towards us, without requiring any

Designing the user interface B Shneiderman and C Plaisant 4th edition Addison Wesley 2004 chapter 7

the door is meant to be pushed open.The affordance we perceive is that it surely will open by pushing the plate.

have to turn it in order to open the door. It's not clear if it's meant to be pushed or pulled open.

towards us, without requiring any

Designing the user interface, B. Shneiderman and C. Plaisant, 4th edition, Addison-Wesley, 2004, chapter 7



Affordance – Example: Media Player

• Buttons on media players have affordance• Buttons on media players have affordance –

• they suggest what they can be used for because we are familiar with similar

• devices slider to shift, buttons to press and dials to turn!

Designing the user interface B Shneiderman and C Plaisant 4th edition Addison Wesley 2004 chapter 7Designing the user interface, B. Shneiderman and C. Plaisant, 4th edition, Addison-Wesley, 2004, chapter 7



Interactive Systems

• Computer Science• Computer Science Application design and engineering of human-computer interfaces

• PsychologyThe application of theories of cognitive processes and the empirical analysis of user behavior

• Sociology and Anthropology Interactions between technology, work, and organization

• Design and Industrial Design Creating interactive productsCreating interactive products



Designing Interactive Systems for Humans

Sociology Psychology Cultural Studies

People

Sociology Psychology Cultural Studies

Ergonomics Anthropology

DesigningElectronic Engineering

Software Engineering

HCI

3D Design & Architecture

Technologies

Designing

Interactive

SystemsDesign

Multimedia Information Design

Interaction DesignDatabase

Product Design

Graphic Design

Communications

Sensors & Actuators

Activities

and

Contexts

Knowledge Management

Business

Change Management

Information Systems

Organizational Psychology

Communities of PracticeContextsChange Management Communities of Practice



Overview

Part IPart I




Part IIPart II







Human Computer Interaction (HCI)

• “Human computer interaction is a discipline concerned with the design• Human-computer interaction is a discipline concerned with the design, evaluation and implementation of interactive computing systems for humanuse and with the study of major phenomena surrounding them” (working definition in the ACM SIGCHI Curricula for HCI [2])(working definition in the ACM SIGCHI Curricula for HCI [2])

• Computer science view point:“I t ti b t h d t ti l“Interaction between one or more humans and one or more computational machines”

f th t “CHI” tti th “H” i th t• some prefer the terms “CHI” – putting the “H”uman in the centre (e.g. CHI conference series)

• alternate terms: human-machine communication, human-machine-interaction, …



Human-Computer Interaction



Human Computer Interaction



Definition of Human-Computer Interaction (1)

“Human Computer interaction (HCI) is the study of interaction between peopleHuman-Computer interaction (HCI) is the study of interaction between people

(users) and computers. It is an interdisciplinary subject, relating computer

science with many other fields of study and research.

Interaction between users and computers occurs at the user interface (or

simply interface), which includes both hardware (i.e. peripherals and othersimply interface), which includes both hardware (i.e. peripherals and other

hardware) and software (for example determining which, and how, information

is presented to the user on a screen).”



Definition of Human-Computer Interaction (2)

“Human computer interaction is a discipline concerned with the designHuman-computer interaction is a discipline concerned with the design,

evaluation and implementation of interactive computing systems for human

use and with the study of major phenomena surrounding them.” (SIG CHI)



What HCI is not about ...

• non information processing• non-information processing

• non-interactive systems

• computer-computer interaction

• ...



This could happen if you do not care about HCI …

The user experience is important ... http://www.youtube.com/watch?v=Vvx3P17rCXY



This could happen if you do not care about HCI …

Even correct mental models might not be enough… http://www.youtube.com/watch?v=V6iDw5ykmwQ&NR=1



People- vs. machine–centered Views

View People are Machines areView People are Machines are

M hi t d iMachine-centered - vague- disorganized- distractible

emotional

- precise- orderly- undistractible

unemotional- emotional- illogical

- unemotional- logical

People-centered - creative - dumbp- compliant- attentive to change- resourceful

- rigid- insensitive to change- unimaginative

- able to make flexible decisions based on context

g- constrained to make consistent decisions

adapted from: Don Norman, Things that make us smart, p. 224, 1993



Human-centered User Interfaces

• do not ask what technology can do but how humans want to use it• do not ask what technology can do, but how humans want to use it

• remember that HCI is not only one end of the interaction: HCI is also a fmediator for human-human interaction

• design with and for humans: user involvement, engagement and evaluationg g g

• remember that most likely the system, the technology and the interface are under parallel development The user interface is not only the add-on to aunder parallel development. The user interface is not only the add on to a highly sophisticated technology, but at the core!

• design for humans: errors slips diversity configurability mappings• design for humans: errors, slips, diversity, configurability, mappings, ...



Human-centered User Interfaces

• study and understand the activities of people and the contexts within which• study and understand the activities of people and the contexts within which some technology might prove useful and hence generate requirements for technologies,

• know the possibilities offered by technologies

• research and design technological solutions that fit in with people, the activities they want to undertake and the contexts surrounding those activities,

• evaluate alternative designs and iterate until a solution is arrived at



Many jobs that require an understanding of HCI

• Interaction designers people involved in the design of all the interactive• Interaction designers - people involved in the design of all the interactive aspects of a product

• Usability engineers people who focus on evaluating products using usability• Usability engineers - people who focus on evaluating products, using usability methods and principles

W b d i l h d l d t th i l d i f• Web designers - people who develop and create the visual design of websites, such as layouts

I f ti hit t l h ith id f h t l d• Information architects - people who come up with ideas of how to plan and structure interactive products

• User experience designers - people who do all the above but who may also carry out field studies to inform the design of products



HCI - An Interdisciplinary Area

• Computer Science• Computer ScienceApplication design and engineering of human-computer interfaces

• Psychology• PsychologyThe application of theories of cognitive processes and the empirical analysis of user behavior

• Sociology and AnthropologyInteractions between technology, work, and organization

• Design and Industrial DesignCreating interactive products

(you just cannot say it often enough – HCI is interdisciplinary!)



HCI - Science, Engineering, and Design Aspects

• the joint performance of tasks by humans and machines• the joint performance of tasks by humans and machines

• the structure of communication between humans and machines

• human capabilities to use machines (including the learnability of interfaces)

• algorithms and programming of the interface itself• algorithms and programming of the interface itself

• engineering concerns that arise in designing and building interfaces

• the process of specification, design, and implementation of interfaces

d i d ff• design trade-offs



Utility, Usability, Likeability

• Utility• Utilitya product can be used to reach a certain goal or to perform a certain task. This is essential!

• Usabilityrelates to the question of quality and efficiency. E.g. how well does a product support the user to reach a certain goal or to perform a certain task.

• Likeabilitythis may be related to utility and usability but not necessarily. People may like a product for any other reason…



Definition: Usability

• What is Usability - Usability 101 by Jakob NielsonWhat is Usability Usability 101 by Jakob Nielson “Usability is a quality attribute that assesses how easy user interfaces are to use. The word ‘usability’ also refers to methods for improving ease-of-use during the design process.”

• Usability has five quality components: – Learnability: How easy is it for users to accomplish basic tasks the first

time they encounter the design?time they encounter the design? – Efficiency: Once users have learned the design, how quickly can they

perform tasks? – Memorability: When users return to the design after a period of not using y g p g

it, how easily can they reestablish proficiency? – Errors: How many errors do users make, how severe are these errors, and

how easily can they recover from the errors? Satisfaction: How pleasant is it to use the design?– Satisfaction: How pleasant is it to use the design?

• In usability studies these qualities are under investigation.



Definition: User Interface Design

User Interface Engineering is a structured approach for designing andUser Interface Engineering is a structured approach for designing and

implementing useful and usable interactive systems.

By following the user interface engineering process the interactive qualities

of a system are ensured.




HCI is Central to the Design and Development Process

• even if done unconsciously Decisions made in the development process… even if done unconsciously. Decisions made in the development process are likely to influence how a product can be used.

• Thinking about the user interface when a first version of a product is finished is too late!G f f ff f• Good user interfaces – and often good products – are a joined effort of all participants in the design and development process

• Software engineering processes fail often because of neglecting usability and the users during the design process – usability is nothing you can do if youthe users during the design process usability is nothing you can do if you have time/budget left at the end of the development process.




It is not Simple to Make Good User Interfaces!

• Basic misconceptions• Basic misconceptions

– If I (the developer) can use it, everyone can use it

– If our non-technical staff can use it, everyone can use it

– Good user interfaces are applied common sense

– A system is usable if all style guidelines are met

• Examples of bad software are easy to find in the WWW or in various “Usability Hall of Shame”

• Creating usable systems is a structured process and can be achieved by use of different methods



Structured Process for Creating Usable Products

• Preconditions:• Preconditions:

– Understanding how people interact with their environment

– Understanding the capabilities and limitations of users

– Basic ergonomics

• Analyze what interaction is required and what technical options are available in a user centered way, evaluate the results of the analysisy y

• Design and prototype user interfaces with user involvement, evaluate prototypes

• Implement an interactive digital product• Implement an interactive digital product

• Test and study the product created

• Usability Engineering is a part of the overall development

• The process is iterative (overall and at each step)



Evolution of the Software Development Process

ProgrammersOriginally

Code/Test Ship

Programmers

ManagersInitiate

Managers

Code/Test Ship

Programmers

Separating testing andd i

p

Managers Programmers QA

T“Loo

Designers

design

M P QAD i

Initiate Code ShipUsability Practitioners

Test k & Feel”

Design beforeprogramming Initiate Design Code Bug Test

User TestShip

Managers Programmers QA

Usability Practitioners

Designers

F A C Ab t F 2 0 [6] Usability PractitionersFrom A. Cooper, About Face 2.0 [6]



Usability - How it does NOT work

• Usability tests at the end when the product is ready and needs to be shippedUsability tests at the end when the product is ready and needs to be shipped• Designing a new and pretty skin to a product • Introducing HCI issues after the system architecture and the foundations are

completed

• Comparison: An interior designer can not make a great house if the architect and engineers forgot windows, set the doors at the wrong locations, and created an unsuitable room layoutcreated an unsuitable room layout.




How to Achieve Usability

(high level overview more details later)(high level overview – more details later)• Identify what utility and usability for the product means

– main purpose of the product– anticipated users target audience– anticipated users, target audience– compare with similar/competing products (if applicable)

• Common effort in the design and development process– trade-offs between design, engineering, and usabilitytrade offs between design, engineering, and usability

• Iterative evaluation– usability testing with different methods at various stages of the

development process• Improvement after product release

– monitoring user behavior– evaluation of changes to the product

(e g adding a new feature to a web shop)(e.g. adding a new feature to a web shop)



Usability Testing I

(high level overview)(high level overview)

• Usability testing of software/web applications assesses several factors, e.g.

– Does application functionality match the user's needs?

I th li ti t l ?– Is the application easy to learn?

– How easy is it for the user to accomplish tasks with the application?

– Is it easy to remember how to use the application?

– Does the user enjoy using the application, or does he/she become easily frustrated by it?

– Does the application do what the user expects?



Usability Testing II

(high level overview)(high level overview)

• Ways to quantify usability include measuring

– How many mistakes get made in a given time period?

– How long do users take to complete a specific task successfully?

– How long it takes for users to learn the application's distinct functions/features

– How repeatable users' experiences are

– What paths do they take in trying?

The users' satisfaction levels– The users satisfaction levels

– How long does it take to correct an error?



Building Successful Digital Products –Not only what users want!

1 What do 3. What can

• tension– different objectives– different design goals 1. What do

people desire?

we build?

Objective:

d e e des g goa s

• step by step 1-2-3j

a product that is desirable and viable

and buildable

• solution– Products in the

overlapping space

• User centered design is not about creating “only” what users want.

2. What will sustain a

F A C Ab t F 2 0business?

From A. Cooper, About Face 2.0



How easy is it to work in multidisciplinary teams?

• Many people are involved in the process of designing and implementing an• Many people are involved in the process of designing and implementing an interactive product

– Different background (design, business, CS, marketing, administration)

– Different objectives– Different objectives

– Different skills

– Different “languages”

• Communication can be very difficult!

– designers and computer scientists do not use the same terms

if th t d d di th “ i i ” th– even if the same terms are used, depending on the “origin”, they may have different meanings

T b bl t k i t i ti l!• To be able to work in a team is essential!

– Team work is a skill that can be learned

– We will force this in the exercises!



Overview

Part IPart I




Part IIPart II







Theories and Models for HCI

• beyond the specifics of guidelines (such as: user interface design guidelines)• beyond the specifics of guidelines (such as: user interface design guidelines)

• principles are used to develop theories

• descriptions/explanatory or predictive

• motor task, perceptual, or cognitive

• Example theories:Example theories:

– Fitts’s law

– Hick’s law

G l O t M th d S l ti l (GOMS)– Goals, Operators, Methods, Selection rules (GOMS) –a cognitive model of procedural knowledge



Theories and Models for HCI

• Explanatory theories:• Explanatory theories:

– observing behavior

– describing activity

– conceiving of designs

– comparing high-level concepts of two designs

– trainingtraining

• Predictive theories:

bl d i t d d i f ti ti– enable designers to compare proposed designs for execution time or error rates



Fitts’s Law

• predictive model of time to point at an object• predictive model of time to point at an object

• the time for hand movements is dependent on the distance to move (D) and the target size (W)

– doubling the distance increases the time, but does not double it

– increasing the target size enables more rapid pointing

• Fitts’s law predicts that the time to acquire a target is logarithmically related p q g g yto the distance over the target size.

• Movement Time (MT) for “gross-movement tasks”:

– MT = a + b log2(D/W + 1)MT = a + b log2(D/W + 1)

– where a = time to start and stop in seconds for a device

– and b = inherent speed of the device, e.g. a mouseM t Ti (MT) f “ i i i ti t k ”• Movement Time (MT) for “precision pointing tasks”:

– PPMT = a + b log2(D/W + 1) + c log2(d/W)

– where c = added constant, dependent on the user’s context

– and d = distance between hand location and spot where the user first touched the screenand d distance between hand location and spot where the user first touched the screen



Fitts’s law in Practice

• MT a + b log (D/W + 1)• MT = a + b log2(D/W + 1)

• D = distance from starting position

• W = size of target along line of (fmotion (for a 2-D target use

smaller of height or depth)

• Common values:a=50ms, b=150ms/bit (empirically measured)

• Further reading: J f R ki Th H I t f ACM P 2000 93 94Jef Raskin, The Humane Interface, ACM Press 2000, pp. 93-94



Fitts’s Law

In its original and strictest form:In its original and strictest form:

• It applies only to movement in a single dimension and not to movement in two dimensions (though it is successfully extended to two dimensions in the Accot Zhai steering law);Accot-Zhai steering law);

• It describes simple motor response of, say, the human hand, failing to account for software acceleration usually implemented for a mouse cursor;

• It describes untrained movements, not movements that are executed after ,months or years of practice (though some argue that Fitts's law models behaviour that is so low level that extensive training doesn't make much difference).



Applications for Fitts’s Law

discuss:discuss:

• linear vs. pie popup menu

f f ?• what places can you think of for a high-precision point task?

• disappearing task bars – Pros? Cons?

• menus at the top of the screen vs. “windows” based



Applications for Fitts’s Law

discuss:discuss:

• linear vs. pie popup menupie menu

f f ?• what places can you think of for a high-precision point task? 4 corners, and at current mouse position

• disappearing task bars – Pros? Cons? fast access; but: row of buttons vs. one taskbar, easy for false triggering –how could you improve that?

• menus at the top of the screen vs. “windows” based



Fitt’s Law

If as generally claimed the law does hold true for pointing with the mouseIf, as generally claimed, the law does hold true for pointing with the mouse,

some consequences for user-interface design include:

• Buttons and other GUI controls should be a reasonable size; it is relatively difficult to click on small ones.

• Edges (e.g. the menu bar at top and Dock at bottom in Mac OS X) and corners of the computer display (e.g. "Start" button in the Luna theme of Windows XP and Apple & Spotlight menus of Mac OS X) are particularly easypp p g ) p y yto acquire because the pointer remains at the screen edge regardless of how much further the mouse is moved, thus can be considered as having infinite width.

• Pop-up menus can usually be opened faster than pull-down menus, since the user avoids traveluser avoids travel.



Fitt’s Law

If as generally claimed the law does hold true for pointing with the mouseIf, as generally claimed, the law does hold true for pointing with the mouse,

some consequences for user-interface design include:

• Pie menu items typically are selected faster and have a lower error rate than linear menu items, for two reasons: because pie menu items are all the same, small distance from the centre of the menu; and because their wedge-shaped target areas (which usually extend to the edge of the screen) are very large.

• Fitts's law remains one of the few hard, reliable human-computer interaction, ppredictive models.

http://en.wikipedia.org/wiki/Fitts_law



Hick’s Law

• The time needed for a person to make a selection is proportional to the log• The time needed for a person to make a selection is proportional to the log number of alternatives given

f• n alternatives of equal probability H = b * log2(n + 1). (b empirically determined constant)

Note:Hick’s law does not applyf

• Alternatives of unequal probabilitypi = the probability of alternative i

if it requires linear search(e.g. a randomly orderedlist of commands in a

H = Σ pi log2(1/pi + 1). menu).It applies if the user cansearch by sub-divisioning.

http://www.usabilityfirst.com

y g



Hick’s Law

• Hick's law is similar in form to Fitts' law Intuitively one can reason that• Hick s law is similar in form to Fitts law. Intuitively, one can reason that Hick's law has a logarithmic form because people subdivide the total collection of choices into categories, eliminating about half of the remainingchoices at each step rather than considering each and every choice one-by-choices at each step, rather than considering each and every choice one-by-one, requiring linear time.

Hi k' l h b h t l i i t h th i• Hick's law has been shown to apply in experiments where the user is presented with n buttons, each having a light bulb beside them. One light bulb is randomly lit up, after which the user must press the corresponding button as quickly as possible Obviously the decision to be made here is verybutton as quickly as possible. Obviously, the decision to be made here is very simple, requiring little conscious thought.



Hick’s Law

• Hick's law is sometimes cited to justify menu design decisions However• Hick s law is sometimes cited to justify menu design decisions. However, applying the model to menus must be done with care. For example, to find a given word (e.g. the name of a command) in a randomly ordered word list (e g a menu) scanning of each word in the list is required consuming linear(e.g. a menu), scanning of each word in the list is required, consuming linear time, so Hick's law does not apply. However, if the list is alphabetical and the user knows the name of the command, he or she may be able to use a subdividing strategy that works in logarithmic time.subdividing strategy that works in logarithmic time.

http://en.wikipedia.org/wiki/Hick's_law



Hick‘s Law

• The selection of complex alternatives is more costly than with easy“/“simple“• The selection of complex alternatives is more costly than with „easy / simple alternatives.

S f f f• Selecting simultaneously from a large number of alternatives is faster than selection sequentially from a small number of alternatives.

• Limits: screen size and short term memory (chunks!)



Hix and Hartson’s guidelines

• User centered design • Give a task based mental model• User centered design

• Know the user

• Involve the user

• Give a task-based mental model

• Be consistent

• Keep it simple

• Prevent user errors

• Optimize user operation

• Keep control with the user

• Design for memory limitations

• Use recognition rather recall

• Use cognitive directnessKeep control with the user

• Help the user to get started

Use cognitive directness

• Draw on real world analogies



Hix and Hartson’s guidelines (2)

• Use informative feedback • Use modes cautiously• Use informative feedback

• Give status indicators

• Use user-centred wording

• Use modes cautiously

• Make user action reversible

• Get attention judiciously

• Use non-threatening wording

• Use specific constructive advice

• Make the system take the blame

• Maintain display inertia

• Organize screen to manage complexityMake the system take the blame

• Do not anthropomorphise

p y

• Accommodate individual difference

• (Hix and Hartson,

• Developing User

• Interfaces, Wiley, 1993)



GOMS: Goals, Operators, Methods, Selection Rules

• GOMS techniques produce quantitative and qualitative predictions of how• GOMS techniques produce quantitative and qualitative predictions of how people will use a proposed system

• Basics:

G ( )– Goals – goal a user wants to accomplish (in real scenarios hierarchical)

– Operators – operation (at a basic level) that are used to achieve a goal

– Methods – sequence of operators to achieve a goalq p g

– Selection Rules – selection of method for solving a goal (if alternatives are given)

• Further reading: John, B. & Kieras, D. (1996). Using GOMS for user interface design and evaluation: which technique? ACM Transactions on Computer-Human Interaction, 3, 287-319.Human Interaction, 3, 287 319.



Quantified User Interface Assessment using GOMS

Operator Short Timename

Tastatureingabe Keying K 0.2 seconds (0.08 – 1.2 seconds

Mauszeigen Pointing P 1.1 seconds (refer to Fitt‘s Law)

Modality change Homing H 0 4 secondsModality changemouse <-> keyb.

Homing H 0.4 seconds

Preparation Mentally M 1 35 seconds to reflect on thePreparation MentallyPrepare

M 1.35 seconds to reflect on the curent goal and the application of a selection rule (refer to Hick‘s Law)Law)

Waiting Responding R N seconds waiting time until the computer has completed the task



GOMS Example

Copy a word from a paragraph to another paragraph 3 pages down “„Copy a word from a paragraph to another paragraph 3 pages down.

With mouse (8 seconds):

H (change to mouse) + P(start) + K(click) + P(mark) + P(menu) +

P(select „copy“) + P(scrollbar) + K(click) + K(click) + K(click) + P(Anfang) +

K(right click) + P(selection: paste) = H + 5xK +6xP = 0.4 + 1 + 6.6 secondsK(right click) + P(selection: paste) H + 5xK +6xP 0.4 + 1 + 6.6 seconds

With keyboard (10.2 seconds):

20 K(C t t t) K( hift“) 7 K( i ht “) K( t l“) K( C“)20xK(Cursor to start) + K(„shift“) + 7xK(„right arrow“) + K(„control“) + K(„C“) +

3xK(„page down“) + 10xK(Cursor to start) + 7xK(„right arrow“) +

K(„right arrow“) + K(„right arrow“) = 51xK g g



Heuristic Rules for Applying the GOMS Model(Card, Moran, Newell)

Rule Description

Rule 0: One M before all KsInsertion of Ms One M before all Ps that select a command, but

not before Ps that select arguments

R l 1 A ti i t d M fl ti tRule 1:Deletion of anticipated Ms

Anticipated Ms are superflous preparation steps as the cognitive preparation has happened in a previous step. Example: mouse movement to click targetExample: mouse movement to click targetM P M K M P K

Rule 2:D l ti f M i iti

Extension of rule 1 to longer, connected ti itiDeletion of Ms in cognitive

unitsactivitiesExample: connected stringsM only at the beginningMKMKMKMK MKKKKMKMKMKMK MKKKK



Heuristic Rules for Applying the GOMS Model(Card, Moran, Newell)

Rule Description

Rule 3: Limiters are characters marking the end of a Deletion of Ms in successive limiters

word. Example: „ „ . , :

R l 4 Li it th t l h t b iRule 4: Deletion of Ms that are limiters of commands

Limiters that always have to be given – e.g. „Enter“. These are added automatically and do not need mental preparation for experienced usersusers.

Rule 5:Deletion of layered Ms

Is an M overlaid by a R (waiting for respond), the M can be deleted.



Potential Implications of a GOMS Analysis

• Large number of Ms (mentally preparing):• Large number of Ms (mentally preparing): why does the user have to „think“ ?

f ( )• Large number of Hs (homing): why does the user have to change between mouse and keyboard so often?

• Many Ps (pointing), but little Ks (keyboard): overloaded control/overloaded GUI ?



Overview

Part IPart I




Part IIPart II







Test: Memorize these numbers!

12391 57123

13819 86129

31923 43119

13812 5618213812 56182

19523 55127

42381 66821

55719 7123155719 71231

57123 44172

You have 1 minute.



Test: Why did it not work?

• What can you do to allow your user to “memorize” better?

wait until the end of this lecture!



Information Transmission

• Human capability of information processing is limited!• Human capability of information processing is limited!

• it is not only of interest, how much information is presented to a human, but

– how much information is transmitted from stimulus to response

– capacity of the information channel

– how rapidly information is transmitted (bandwidth)how rapidly information is transmitted (bandwidth)



Information Channels

N i

Information Channel

Noise

H HHT

Hs HR

Hs = Information, stimulusH I f ti l tHloss = Information, lost

HR = Information, receivedHT = Information, transmitted

Hloss



Question

• How would you describe “human” information processing?• How would you describe human information processing?

• Why is it important to know about how humans process information?



Human Information Processing

Human

I tHuman

Human

Input(the senses)

OutputHuman

InformationProcessing

OutputCentral

ProcessingInput

(e.g. monitors)Processing

Unit(e.g. keyboard)

Computer1/27/2011 85Prof. Dr. Matthias Kranz



Att ti

Memory

Motivations Attention

Initiall i

Motor Awareness Affect

analysis systems

Detection Output fromby

senses

Output fromspeech, muscles

etc.

Designing Interactive Systems, D. Benyon, P. Turner and S. Turner, 2005, Addison-Wesley, p. 101




Engineering Psychology and Human Performance; C. Wickens and J. Hollands, 1999, Prentice Hall, p. 11image source: http://www.hf.faa.gov/Webtraining/Cognition/CogFinal008.htm



HIP: Senses




Definition: Senses

• A sense is “a system that consists of a sensory cell type (or group of cell• A sense is a system that consists of a sensory cell type (or group of cell types) that respond to a specific kind of physical energy, and that correspond to a defined region (or group of regions) within the brain where the signals are received and interpreted ”received and interpreted.



HIP: Senses

• senses as our “windows to the world”• senses as our windows to the world

• five major senses: sight, hearing, touch, smell, taste

• other senses: thermoception, nociception, equilibrioception, proprioception

• other beings have different and/or additional senses

• human senses are far from being perfect!

• the senses limit what we can perceive – this can only, if at all, be extended bythe senses limit what we can perceive this can only, if at all, be extended by technical means!

• capabilities of our senses change over time (e g hearing)• capabilities of our senses change over time (e.g. hearing)

• Example for utilizing this in a user interface: “old” people do not hear hightones as good as “young” people. This has been used to “noise” away young people hanging around with otherwise unhearable soundsyoung people hanging around with otherwise unhearable sounds.



HIP: Short-Term Sensory Storage (STSS)





• “Sensory Memory is the retention for brief periods of time of the effects of• Sensory Memory is the retention, for brief periods of time, of the effects ofsensory stimulation.” (Goldstein, p. 140)

f f collecting information for processing

holding information briefly while initial processing is going on

filling in the blanks when stimulation is intermittent (bad for witnesses….)g ( )(from: Goldstein, p. 145)

Cognitive Psychology: Connecting Mind, Research and Everyday Experience, E.B. Goldstein, 2004, Wadsworth Publishing p 136Wadsworth Publishing, p. 136

online: http://64.78.63.75/samples/05PSY0304GoldsteinCogPsych.pdf




sensory systems can “store” perceptions after the stimulus sensory systems can store perceptions after the stimulus

STSS does not need explicit attention, it works preattentive

STSS is located in the brain

STSS is not part of the conscious memory

STSS != short term memory (it’s working memory, anyways…)

two most important types of short-term sensory memory:two most important types of short term sensory memory:

echoic memory (lasts ~ 2-10 sec. after stimulus)

iconic memory (lasts ~ 0.5-1.0 sec. after stimulus)

examples:

echoic memory: “What did you say?”

iconic memory: grid of letters




DHFG

VJSAVJSA

LKOP




• grid of letters: George Sperling (1960) presented participants a grid of three• grid of letters: George Sperling (1960) presented participants a grid of three rows of four letters for:

• two variants:

• report as many letters as possible

• report a specific rowp p

• In the latter case, participants usually manage to report the full row (four letters)!letters)!



HIP: Perception




HIP: Perception

• perception• perception

• driven by sensory inputs bottom-up

• driven by long-term memory top-down

• example:

• bottom-up: clear sensory information, e.g. bright red light at crossingbottom up: clear sensory information, e.g. bright red light at crossing

• top-down: sensory information is poor/ambiguous: perception influenced by expectations and past experiences stored in our long term memory

(no joke! – in a bad mood, all is perceived differently)

• Yoda: “Du darfst niemals vergessen: Deine Wahrnehmung bestimmt deineRealität!“

• Yoda: “Remember that it is our perception that creates our reality!”



HIP: Attention




HIP: Attention

• Attention is the cognitive process of selectively concentrating on one aspect of• Attention is the cognitive process of selectively concentrating on one aspect of the environment while ignoring other things.

• attention as crucial element for cognitive processes as learning or task executionexecution

• types of attention:

• selective attention: Selective attention is the focusing of one’s conscious awareness on a particular stimulus.

• focused attention: The ability to respond discretely to specific visual, y p y p ,auditory or tactile stimuli.

• divided attention: highest level of attention; refers to the ability to respond simultaneously to multiple tasks or multiple task demands.simultaneously to multiple tasks or multiple task demands.

• example: “scanning” of information is usually driven by experience (knowing where to look for) top down processwhere to look for) – top-down process



HIP: Attention Models

• allocation model (Kahneman 1973)• allocation model (Kahneman, 1973)

• limited amount of “processing power” at our disposal

• task execution depends on how much of our attention “capacity” we can spare on it

• controlled and automatic attention (Schneider and Shiffirn, 1977)

• controlled processing makes heavy demands on attentional resources, is slow and limited in capacity, and involves consciously directing attention towards a task

• automatic processing makes no demands on attentional resources, is fast, unaffected by capacity limitations, unavoidable and difficult to modify, and is not subject to conscious awareness



HIP: Attention Models

A il bl M if t tiAvailablecapacity

Manifestationsof arousal

Kahneman’s capacity allocation model

Enduringdispositions

AllocationEvaluation

Momentary

Allocationpolicy

of demandson capacity

intentions

Possibleactivities

ResponseDesigning Interactive Systems; D. Benyon, P. Turner and S. Turner; 2005, Pearson, p. 374

p



HIP: Selective Attention

• needed for e g perception or learning (visual sampling or scanning)• needed for e.g. perception or learning (visual sampling or scanning)

• being too selective is referred to as “cognitive tunneling”

• negative examples: selecting cues that stand out rather than useful ones (e.g. during a presentation/argumentation)g p g )

• important to select the right stimulus source!



HIP: Focused Attention

• concentration on one stimulus source• concentration on one stimulus source

• difficult: humans have tendency to be distracted

• important e.g. for directing attention to warning/error messages

• differences in errors between selective attention and focused attention: intentional selection of the wrong source vs. unintentional external influences

• important to focus on one stimulus source (for some tasks)!



HIP: Attention

• refer to the attention models• refer to the attention models

• limited attention capacity of humans

• important e.g. for layout of instruments in a cockpit (see Gestalt laws)

• differences in errors between focused attention and divided attention: some of our attention is directed to stimuli we do not wish to process vs. our limit to attend to all stimuli we wish to process

• only a certain maximum of attention capacity can be divided to tasks only a certain maximum of attention capacity can be divided to tasks



HIP: Attention

• Attention can be directed at a particular task and/or divided between a number• Attention can be directed at a particular task and/or divided between a number of different tasks

• Practice reduces the amount of attention required by a particular task. (e.g. typing blindly on a keyboard while reading a text)typing blindly on a keyboard while reading a text)

• Attention and awareness are closely linked.

Designing Interactive Systems; D. Benyon, P. Turner and S. Turner; 2005, Pearson, p. 108



HIP: Vigilance

• “Vigilance is an aspect of attention which refers to detecting a rare event or• Vigilance is an aspect of attention which refers to detecting a rare event or signal in a desert of inactivity or noise”1

• vigilance: detect signals over a long period of time; the signals are intermittent, unpredictable and infrequent2unpredictable, and infrequent2

• examples of vigilance tasks:

• security inspector x-raying luggage

• quality control in production

• vigilance level (steady-state level performance)

• vigilance decrementvigilance decrement

1Designing Interactive Systems; D. Benyon, P. Turner and S. Turner; 2005, Pearson, p. 1092Engineering Psychology and Human Performance; C. Wickens and J. Hollands, 1999, Prentice Hall,

p. 34-36



HIP: Vigilance Paradigms (selection)

• free response paradigm:• free-response paradigm:

• a target event occurs at any time

• non-events are not defined

• example: power plant monitor supervision

• inspection paradigm:

• events occur at fairly regular intervalsevents occur at fairly regular intervals

• some are events, most are non-targets

• example: quality control (most items are ok, only some have defects)

Engineering Psychology and Human Performance; C. Wickens and J. Hollands, 1999, Prentice Hall, p. 35



HIP: Vigilance Paradigms 1

• free response paradigm:• free-response paradigm:

• a target event occurs at any time

• non-events are not defined

• example: power plant monitor supervision

• inspection paradigm:

• events occur at fairly regular intervalsevents occur at fairly regular intervals

• some are events, most are non-targets

• example: quality control (most items are ok, only some have defects)





• successive vigilance paradigm:• successive vigilance paradigm:

• target stimulus has to be remembered

• successive events have to be compared to the target stimulus

• example: detect if a color is darker than the initial target

• simultaneous vigilance paradigm:

• all events/information needed for discrimination are present at the sameall events/information needed for discrimination are present at the same time

• example: compare many types of garment to a standard piece of fabric

E i i P h l d H P f C Wi k d J H ll d 1999 P ti H llEngineering Psychology and Human Performance; C. Wickens and J. Hollands, 1999, Prentice Hall, p. 35




• sensory vigilance paradigm:• sensory vigilance paradigm:

• signals represent changes in the auditory or visual intensity

• example: color changes

• cognitive vigilance paradigm:

• signals represent “information”: symbolic or alphanumeric stimuli

• example: proofreading a manuscriptexample: proofreading a manuscript




HIP: Memory




HIP: Memory

• “Memory is the process involved in retaining retrieving and using information• Memory is the process involved in retaining, retrieving, and using information about stimuli, images, events, ideas, and skills after the original is not longer present.” 1

• “ ... without the capacity to remember and to learn, it is difficult to imagine what life would be like, whether it could be called living at all. Without

ld b t f th t ith thi b t i tmemory, we would be servants of the moment, with nothing but our innate reflexes to help us deal with the world. There could be no language, no art, no science, no culture. “2

1Cognitive Psychology: Connecting Mind, Research and Everyday Experience, E.B. Goldstein, 2004, Wadsworth Publishing, p. 136

online: http://64.78.63.75/samples/05PSY0304GoldsteinCogPsych.pdf2C. Blakemoore, The Mind Machine, 1988, BBC Publications

Designing Interactive Systems; D. Benyon, P. Turner and S. Turner; 2005, Pearson, p. 352



HIP: Memory

• Nuremberg Funnel (German: Poetischer Trichter“) Georg Philipp Harsdörffer• Nuremberg Funnel (German: „Poetischer Trichter ), Georg Philipp Harsdörffer (1607-1658): „Die Teutsche Dicht- und Reimkunst, ohne Behuf der lateinischen Sprache, in VI Stunden einzugießen“



HIP: Memory

• human memory consists of two major components:• human memory consists of two major components:

• working memory (formerly: short-term memory (was: separate memory))

• long-term memory

• memory “processes”:

• recallrecall

• recognition

• chunking

h l• rehearsal

• NOT: database (Nuremberg Funnel)

• human memory is multi-modal!



HIP: Working Memory (WM)

• memory storage for up to 30 seconds after that short period the contents• memory storage for up to 30 seconds, after that short period, the contents decay or are displaced

• rapid access: ~70ms access time

( O )• storage size: 3-4 “chunks” (NOT: 7+-2 elements!)

• it is easy to overwrite the contents (intentionally and unintentionally!)

• can store two different types of data at the same time:yp

• visual information (visuo-spatial sketchpad)

• verbal information (articulatory loop)

• to maintain the contents of working memory: rehearsal is needed• to maintain the contents of working memory: rehearsal is needed

• to persistently store information from working memory: move it to long-term memory

Designing Interactive Systems; D. Benyon, P. Turner and S. Turner; 2005, Pearson, p. 104-105, 352ff



HIP: Long-Term Memory (LTM)

• unlimited in capacity• unlimited in capacity

• lasts from a few minutes to life time

• slow access: 1/10 seconds access time

• multi-modal memory

• smell as strong trigger to long-term memory example: perfume of your first friend

• sound as most efficient cue for working memory

• three types:

• episodic serial memory of events• episodic – serial memory of events

• procedural – knowledge of how to do things

• semantic – structured memory of facts, concepts, skills

• semantic LTM derived from episodic LTM




• Semantic memory structure• Semantic memory structure

• provides access to information

• represents relationships between bits of information

• supports inference

• Model: semantic networkModel: semantic network

• inheritance – child nodes inherit properties of parent nodes

• relationships between bits of information explicit

t i f th h i h it• supports inference through inheritance




• Forgetting:• Forgetting:

• decay: information is lost gradually, but very slowly

• interference

• new information replaces old: retroactive interference

• old may interfere with new: proactive inhibition

• affected by emotion – one can subconsciously `choose' to forgetaffected by emotion one can subconsciously choose to forget



HIP: Memory Processes 1

• Encoding is the process by which information is stored in memory• Encoding is the process by which information is stored in memory.

• Retrieval is the means by which memories are recovered from long-term storage.

• Forgetting is the name of a number of different possible processes by which g g p p ywe fail to recover information.



HIP: Memory Processes 2

• recall (“Erinnerung”): active memory search to retrieve a particular piece of• recall ( Erinnerung ): active memory search to retrieve a particular piece of information

( )• recognition (“Wiedererkennung”): searching the memory and deciding whether the retrieved piece of information matches a given information; recognition is generally easier and quicker than recall

• rehearsal: The process of repeating information in working memory . This facilitates the short-term recall of information and its transfer to long-term memory.

• the amount stored is proportional to the number of rehearsals!

• chunking: grouping of items into more meaningful units (e.g. 00495313913263 in 0049 531 391 3263)



HIP: Memory




Motivation for Decision Making and Long-Term Memory

• Do dogs bark? Yes/No• Do dogs bark? Yes/No

• Do dogs breathe? Yes/No

• The second question takes longer to answerThe second question takes longer to answer

this indicates semantic coding!

without memory, there is no “thinking” or decision-making!



HIP: Decision Making

• after the perception of the stimulus a response needs to be selected• after the perception of the stimulus, a response needs to be selected

• Automatic vs. controlled decisions

• automatic: fast

• little or no attention required

• learned reflexes or behavior

• a long-term memory procedure is executed nearly automatically ina long term memory procedure is executed nearly automatically in response to the stimulus

• controlled: slow

• attention required typically conscious of thoughts• attention required, typically conscious of thoughts

• interaction with working memory (WM) and long-term memory (LTM) systems

• cf. “planning problem” e.g. from robotics (top-down or bottom-up, task separation)



HIP: Memory




HIP: Response and Feedback

• after a decision has been made it has to be executed by complex motor• after a decision has been made, it has to be executed by complex motor movements

• feedback-loop: we observe the consequences of our actions, producing closed loop feedbackclosed-loop feedback

• the model is circular rather than linear (see HIP model)



Human Information Processing – Short Term Memory Test...




Overview

Part IPart I




Part IIPart II







HIP: Visual Perception

• Visual perception is the process of extracting meaning from sensory• Visual perception is the process of extracting meaning from sensory information. It is concerned with recognition and understanding.

• Vision is an easier process concerned with detecting color, shapes or edges of objects. Vision does not necessary require and understanding of the world surrounding us.

Designing Interactive Systems, D. Benyon, P. Turner and S. Turner, 2005, Addison-Wesley, p. 110-113




Vision:• red triangular shape• 2 rectangular shapes

Visual Perception:• house• door2 rectangular shapes

• b/w lines ...door

• roof ...




Visual perception is hard to study:– Visual perception is hard to study:

- we seamlessly perceive our environment

- perception usually “works”

- how to understand something so basic and given to everyone?

– R. Gregory (1973) used a constructivist approach to perception: studyingR. Gregory (1973) used a constructivist approach to perception: studying perception when it fails!

– Thereby, we can understand why it fails and how it works.



HIP: Visual Illusions – Müller-Lyer Illusion

• Both lines are equally long. The bottom line thus looks shorter.



HIP: Visual Illusions – Necker Cube

• Which cube do you see? There are two possible cubes.

• As our brain tries to make sense, both versions “swap”.



HIP: Gestalt Laws

• The Gestaltists a group psychologists identified a number of properties that• The Gestaltists, a group psychologists, identified a number of properties that can be regarded as innate to all humans. Thus, their findings are called Gestalt Laws.

Gestalt Laws:

• proximity

• continuity

• part-whole relationships

• similaritysimilarity

• closure




HIP: Gestalt Law - Proximity

Objects that are close in space or time

tend to be perceived together.g

This can be used e.g. for UI

arrangement of buttons or informationarrangement of buttons or information.



HIP: Gestalt Law - Continuity

– We tend to perceive smooth, continuous patterns instead of disjoint, interrupted patterns.



HIP: Gestalt Law – Part-Whole Relationship

HH H

HH HH H HH

HHH

H H HH

HH

H HH H HHH

H HH H H

S t diff t h l

H H H HH H H

• Same parts, different whole: while both figures are made from the letter “H”, the whole is perceived differently:

The left figure is perceived as big H, while the right is not.



HIP: Gestalt Law – Similarity

Si il fi t d t b d t th• Similar figures tend to be grouped together.

• The figure above shows two rows of circles and one row of rectangles. g g

• The figure above shows 6 columns of three-shape elements.



HIP: Gestalt Law – Closure

• Closed figures are perceived more easily than incomplete or open figures.g g

• The figure either shows four triangles or a Maltese cross.



HIP: Depth Perception

• The arrangement of our visual sensors (eyes) allows us to perceive our world• The arrangement of our visual sensors (eyes) allows us to perceive our world three-dimensionally.

f• There two types of depth cues:

• primary depth cues (relevant e.g. to immersive virtual reality systems)

• secondary depth cues (more relevant e.g. to non-immersive applications y p ( g ppsuch as games)



HIP: Depth Perception – Primary Depth Cues

The four primary depth cues are retinal disparity stereopsis accommodationThe four primary depth cues are retinal disparity, stereopsis, accommodation and convergence.

• retinal disparity: As our eyes are approximately 7 cm apart, each retina receives a slightly different image of the world This is processed by the brainreceives a slightly different image of the world. This is processed by the brain and interpreted as distance information.

• stereopsis: Stereopsis is the process by which the different images of the ld i d b h bi d t d i l th di i lworld received by each eye are combined to produce a single three-dimensional

experience.

• accommodation: This is a muscular process by which we change the shape f th l i i d t t h l f d i Thof the lens in our eyes in order to create a sharply focused image. The

information from the muscles is unconsciously used for depth information.

• convergence: Over distances of 2-7 meters we move our eyes more and more inwards to focus on an object at these distances. This process is used to provide additional depth information.




HIP: Depth Perception – Secondary Depth Cues

The secondary depth cues are the basis for depth perception on twoThe secondary depth cues are the basis for depth perception on two-dimensional displays. The secondary depth cues are:

• light and shade: an object with light and shadow improves the depth perceptionperception

• linear perspective: shadow on arrow

• height in the horizontal plane:

• motion parallax: riding on a train and looking out of the window: near objects are perceived to flash by quickly, objects further away as slower.

• overlap: e.g. overlapping windows in a GUIp g pp g

• relative size: see sun + cloud

• texture gradient: texturedsurfaces appear closersurfaces appear closer




HIP: Factors affecting Perception

expectations motivation

individualpast perceptual individualdifferences

pastexperience

perceptualset

affect culturalaffect factors




Overview

Part IPart I




Part IIPart II







HIP: Memory Design Guidelines 1

• M1: Organize information into a small number of “chunks”• M1: Organize information into a small number of chunks .

• M2: Try to create short linear sequences of tasks.

• M3: Use persistence, so do not flash important information onto the screen for brief time periodsfor brief time periods.

• M4: Do not “overwrite” the contents of working memory by giving additional tasks to the user.

• M5: Organize data fields to match user expectations or to organize user input• M5: Organize data fields to match user expectations or to organize user input (e.g. the automatic formatting of phone numbers)

• M6: Provide reminders or warnings of the state the user has reached in an operation.p




HIP: Memory Design Guidelines 2

• M7: Provide ongoing feedback on what is happening and/or what has just• M7: Provide ongoing feedback on what is happening and/or what has just happened. Bad example: BSOD – no information here will help the ordinary user to avoid the problem next time.

• M8: The user interface should behave in consistent ways at all the times for all screens.

• M9: Terminology, icons and the use of colour should be consistent between screens.




Overview

Part IPart I




Part IIPart II







Human Error – Designing Interactive Systems for Humans

• “There is no medicine against death and against error no rule has been• There is no medicine against death, and against error no rule has been found.” (Sigmund Freud)

• “If an error is possible, someone will make it” (Don Norman)

f ( )• “If something can go wrong, it will.” (and in the worst possible way...) (Murphy)

• “Let me put it this way, Mr. Amor. The 9000 series is the most reliable computer ever made. No 9000 computer has ever made a mistake or p pdistorted information. We are all, by any practical definition of the words, foolproof and incapable of error.” (HAL, 2001: A Space Odyssey)

• “... The catastrophe has been attributed to human error ...” – or maybe, the... The catastrophe has been attributed to human error ... or maybe, the interface should also be blamed for allowing erroneous actions! (e.g. Space Odyssey 2001 – Computer HAL) (HAL != IBM)



Human Error – Designing Interactive Systems for Humans

• human error may also be a starting point to look for design problems!• human error may also be a starting point to look for design problems!

• design implications:

– assume all possible errors will be made (Murphy’s law is true)

– minimize the chance to make errors (constraints – limit options)

– minimize the effect that errors have (is difficult!)minimize the effect that errors have (is difficult!)

– include mechanism to detect errors (“other users that have done this have also done …” ???)

attempt to make actions reversible– attempt to make actions reversible(unlimited undo copy & paste)



Human Error – Understanding Errors

• Errors are routinely made!• Errors are routinely made!

– communication and language is used between people to clarify – more often than one imagines

f– common understanding of goals and intentions between people helps to overcome errors

• Two fundamental categories of errors:

– mistakes

• overgeneralization• overgeneralization

• wrong conclusions

• wrong goal

– slips

• result of “automatic” behaviour

• appropriate goal but performance/action is wrongpp p g p g



Definition: Error

human error: the result of any action whose consequences are not what washuman error: the result of any action whose consequences are not what wasintended by the person performing the action. Errors are commonly classified as slips (automatic processes interfering with an action) or mistakes (failures in reasoning or selection of sub goals) Minimization of errors is a frequent designreasoning or selection of sub goals). Minimization of errors is a frequent design goal and often trades off with the speed at which tasks can be performed.

t it ti i hi h th t t d th h thcomputer error: a situation in which the computer cannot proceed through the normal or expected course of a task because of a bug in the software, an incorrect piece of code that doesn't properly handle unexpected inputs or performs its calculations incorrectly In this situation a system typically producesperforms its calculations incorrectly. In this situation, a system typically produces an error message for the user, and the program may either fail or enter an error-recovery process to enable to continue working despite an individual failed task.

http://www.usabilityfirst.com/glossary/main.cgi?function=display_term&term_id=653



Definition: Slip

(psychology) an error resulting from skilled behavior being performed at a time(psychology) an error resulting from skilled behavior being performed at a time when it shouldn't, such as accidentally driving to the office when you intended to drive to the store.

Highly-practiced behaviors become automatic and the triggers for these automatic behaviors may cause them to be performed at a time when an lt ti i i talternative is more appropriate.

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Types of Slips (Errors!) - 1

• capture error a frequently done activity takes charge of (captures) the one• capture error – a frequently done activity takes charge of (captures) the one intended (e.g. counting 1,2,...,9,10,Jack,Queen,King)

• description error – the intended action has much in common with others that are possible (e.g. throwing dirty clothes in the toilet instead of the laundry basket)

• data-driven error – data-driven activities can intrude into an ongoing action sequence (e.g. dialing a room number instead of telling someone the room number on the phone)

The Design of Everyday Things, D. Norman, Currency DoubleDay, 1990, chap. 5



Types of Slips (Errors!) - 2

• associative activation error internal associations trigger actions (e g the• associative activation error – internal associations trigger actions (e.g. the phone rings and you answer “come in” – both knocking on your door and your phone ringing require “greeting” actions)

• loss-of-activation error – forgetting; an error that occurs when, after beginning a goal-directed behavior, the reason for starting it is forgotten (completely or i t !) ( i t th kit h b t f tti h )in parts!) (e.g. going to the kitchen, but forgetting why)

• mode error - devices have different modes of operation and in those modes, actions have different meanings (e.g. a watch with stop watch functionality: in one mode, the light is turned on, in stopwatch mode, the time is reset to 0)

The Design of Everyday Things, D. Norman, Currency DoubleDay, 1990, chap. 5



Human Error – Implications on Design

• principles of good design (D Norman)• principles of good design (D. Norman)

– stage and action alternatives should be always visible

– good conceptual model with a consistent system image

– interface should include good mappings that show the relationship between stages

– continuous feedback to the user

• critical points/failures

inadequate goal formed by the user– inadequate goal formed by the user

– user does not find the correct interface / interaction object

– user many not be able to specify / execute the desired action

– Inappropriate / mismatching feedback



Human Error – Error Avoidance Design Guidelines

• E1: Use knowledge in the world and in the head of in order to promote a• E1: Use knowledge in the world and in the head of in order to promote a good conceptual model of the system on the part of its users; this requires consistency of mapping between the designer’s model, the system model and the user’s modeland the user s model.

• E2: Simplify the structure of tasks so as to minimize the load upon vulnerable cognitive processes such as working memory, planning or problem solving.

E3 M k b th th ti d th l ti f ti i ibl Vi ibilit• E3: Make both the execution and the evaluation of an action visible. Visibility in regard of the former allows the user to know what is possible and how things should be done; visibility on the evaluation side enables people to gauge the effects of their actionsgauge the effects of their actions.





• E4: Exploit natural mappings between intentions and possible actions• E4: Exploit natural mappings between intentions and possible actions, between actions and their effects on the system state and what is perceivable, and between the system state and the needs, intentions and expectations of the userexpectations of the user

• E5: Exploit the power of constraints, both natural and artificial. Constraints guide the user to the next appropriate action or decision.

E6 D i f A th t th ill h th l f• E6: Design for errors. Assume that they will happen, then plan for error recovery. Try to make it easy to reverse operations and hard to carry out non-reversible ones. Exploit forcing functions such as wizards which constrain the user to a limited range of operationsuser to a limited range of operations.





• E7: When all else fails standardize actions outcomes layouts displays etc• E7: When all else fails, standardize actions, outcomes, layouts, displays, etc. The disadvantages of less than perfect standardization are often compensated for by the increased ease of use. But standardization for its own sake is only a last resort The earlier principles should always be appliedown sake is only a last resort. The earlier principles should always be applied first.




Overview

Part IPart I




Part IIPart II







Questions?

Matthias Kranz([email protected])


human-ctcomputer-it tiinteraction it d ti &sl tdt iintroduction … · 2012-02-05 ·...

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