May 18, 2010IAT 3343 Why We Are Here Look at human factors that affect software design and development Central Topic: User interface design
May 18, 2010IAT 3344 HCI What happens when a human and a computer get together to perform a task –Task Write a document Plan a budget Design a presentation Play a video game –Not a task.. Goof off (obviously)
May 18, 2010IAT 3345 Why is this important? Computers (in one way or another) affect every person in society –Increasing % use computers in work, at home in the road… Product success depends on ease of use
May 18, 2010IAT 3346 Course Aims Consciousness raising for you –Eg. Don Norman “The Design of Everyday Things” –Doors Handles afford various opening method Design critic
May 18, 2010IAT 3347 Goals of HCI (Shneiderman & Plaisant Chap1) Allow users to carry out tasks –Safely –Effectively –Efficiently –Enjoyably
May 18, 2010IAT 334 Goals of System Engineering Functionality Tasks and sub-tasks to be carried out Reliability Maintaining trust in the system Standardization, integration, consistency and portability Schedules and budgets Adhering to timelines and expense Human factors principles and testing reduces costs
May 18, 2010IAT 3349 Usability Five Measurable Goals of UI Design Combination of –Ease of learning –High speed of user task performance –Low user error rate –Subjective user satisfaction –User retention over time
May 18, 2010IAT 334 Life-critical systems: air traffic control, emergency, power utilities etc. high reliability, error-free performance, lengthy training for systems, subjective satisfaction less of an issue Industrial and commercial uses: banking, inventory management, airline and hotel reservations, etc. low costs is critical over reliability, ease of learning, errors calculated against costs, subjective satisfaction of modest importance Interests in Human Factors in Design
Sept14, 2009IAT 334 Office, home, entertainment: productivity and entertainment applications ease of learning, low error rates, subjective satisfaction are paramount since use is discretionary and competition is fierce. Range of types of users from novice to expert. Exploratory, creative, and cooperative: web-based, decision- making, design-support, collaborative work, etc. users knowledgeable in domain but vary in computer skills, direct- manipulation using familiar routines and gestures work best, difficult systems to design and evaluate. Interests in Human Factors in Design
May 18, 2010IAT 334 Accommodating Human Diversity Physical Abilities and Workplaces Cognitive and Perceptual Abilities Personality Differences Cultural and International Diversity Users with Disabilities Elderly Users
May 18, 2010IAT Key Historical Event Design of the first Mac “The computer for the rest of us”
May 18, 2010IAT Two Crucial Errors Assume all users are alike Assume all users are like the designer
Another Crucial Error Have the user design it! Users bring vital knowledge to design: –They know a lot about the problem –They know a lot about the current tools –They typically know very little about design May 18, 2010IAT 33416
May 18, 2010IAT UI Design/Develop Process Analyze user’s goals Create design alternatives Analyze designs Implement prototype Test Refine Design Evaluate Implement
May 18, 2010IAT Evaluation Things we can measure –Time to learn –Speed of performance –Rate of errors by user –Retention over time –Subjective satisfaction
May 18, 2010IAT Interfaces in the World VCR Mouse Phone Copier Car Airline reservation Air traffic control
May 18, 2010IAT History of HCI ______________________________________________________________________________________ SCHOOL OF INTERACTIVE ARTS + TECHNOLOGY [SIAT] |
May 18, 2010IAT Ivan Sutherland SketchPad - ‘63 PhD thesis at MIT –Hierarchy - pictures & subpictures –Master picture with instances –Constraints –Icons –Copying –Light pen as input device –Recursive operations
May 18, 2010IAT Douglas Engelbart Invented the mouse Landmark system/demo: –hierarchical hypertext, multimedia, mouse, high-res display, windows, shared files, electronic messaging, CSCW, teleconferencing, …
May 18, 2010IAT 334 The Mouse source: resonancepub.com & brittanica.com Doug Engelbart’s mouse
May 18, 2010IAT Alan Kay Dynabook - Notebook sized computer loaded with multimedia and can store everything Personal Computing Desktop Interface
May 18, 2010IAT PCs with GUIs Xerox PARC - mid 1970’s –Alto –Local processor, Bitmap display, Mouse –Precursor to modern GUI –LAN - Ethernet
May 18, 2010IAT 334 Menus source: folklore.org Bill Atkinson’s Polaroids of the first pull-down menu prototype - circa 1979
May 18, 2010IAT Xerox Star - ‘81 First commercial PC designed for “business professionals” –Desktop metaphor, pointing, WYSIWYG First system based on usability engineering
May 18, 2010IAT Human Capabilities Want to improve user performance Know the user! –Senses –Information processing systems
May 18, 2010IAT Senses Sight, hearing, touch important for current HCI –smell, taste ???
May 18, 2010IAT Sight Visual System workings Color - color blindness: 8% males, 1% females Much done by context & grouping (words, optical illusions, …)
May 18, 2010IAT Hearing Often taken for granted how good it is –Pitch - frequency –Loudness - amplitude –Timbre - type of sound (instrument) Sensitive to range 20Hz Hz Limited spatially, good temporal performance
May 18, 2010IAT Touch Three main sensations handled by different types of receptors: –Pressure (normal) –Intense pressure (heat/pain) –Temperature (hot/cold) Where important?
May 18, 2010IAT Models of Human Performance Predictive Quantitative –Time to perform –Time to learn –Number and type of errors –Time to recover from errors Approximations
May 18, 2010IAT Basic HCI Model Human Processor –A simple model of human cognition –Card, Moran, Newell 1983 Components: –Senses –Sensory store –Short-term memory –Long-term memory –Cognition
May 18, 2010IAT Information Processing Usually serial action –Respond to buzzer by pressing button Usually parallel recognition Driving, reading signs, listening to radio
May 18, 2010IAT Model Human Processor Basics Parameters –Processors cycle time of ms –Memories have type, capacity, decay time Types –Visual –Auditory –Tactile –Taste, smell, proprioception, etc
May 18, 2010IAT Model Picture Closeup
May 18, 2010IAT Perceptual Processor Continually “grabs data” from the sensory system Cycle time: 100ms [ ] ms Passes data to Image Store in unrecognized form –“Array of Pixels” (or whatever it is) from eyes –“Sound Intensities” from ears
May 18, 2010IAT Sensory Store The “input buffer” of the senses Stores most recent input unrecognized Storage time and capacity varies by type –Visual: NominalRange Capacity:17letters of text[7 - 17] letters Decay Time:200ms [ ] ms –Audio: Capacity:5 letters of text [ ] letters Decay Time: 1500 ms[ ] ms
May 18, 2010IAT Memory Three “types” –Short-term memory Conscious thought, calculations –Intermediate Storing intermediate results, future plans –Long-term Permanent, remember everything ever happened to us
May 18, 2010IAT Memory: Sort Term Short Term (Working) Memory (WM) –Gets basic recognition from Sensory Store “Stop sign” vs. “red octagon w/white marks” –7 +/- 2 “chunks” vs –WM: NominalRange Capacity:7 chunks[5 - 9] chunks Decay Time:7 seconds [ ] seconds Access Time:70ms[ ] ms
May 18, 2010IAT Memory: Long Term Long Term Memory (LTM) –“Unlimited” size –Slower access time (100ms) –Little decay –Episodic & Semantic Why learn about memory? –Know what’s behind many HCI techniques –Predict what users will understand
May 18, 2010IAT LT Memory Structure Episodic memory –Events & experiences in serial form Semantic memory –Structured record of facts, concepts & skills
May 18, 2010IAT Read the colors of the words Black Red Orange Yellow Blue
May 18, 2010IAT MHP Operation Recognize-Act Cycle –On each cycle, contents in WM initiate actions associatively linked to them in LTM –Actions modify contents of WM Discrimination Principle –Retrieval is determined by candidates that exist in memory relative to retrieval cues –Interference by strongly activated chunks
May 18, 2010IAT Perception Stimuli that occur within one PP cycle fuse into a single concept –movies (frame rate) Frame rate > 1 / Tp = 1/(100 msec/frame) = 10 f/sec –morse code listening rate Perceptual causality –two distinct stimuli can fuse if the first event appears to cause the other –events must occur in the same cycle
May 18, 2010IAT Operation Variable Cognitive Processor Rate –Cognitive Processor cycle time Tc is shorter with greater effort –Induced by increased task demands/information –Decreases with practice
May 18, 2010IAT Operation: Target finding Task: Move hand to target area Fitts Law –A series of microcorrections Correction takes Tp + Tc + Tm –Time Tpos to move hand to target width W which is distance D: Tpos = a + b log 2 (d/w + 1.0) –Movement time depends on relative precision
Jan 13, 2011IAT IAT 334 Interface Design Task Analysis ______________________________________________________________________________________ SCHOOL OF INTERACTIVE ARTS + TECHNOLOGY [SIAT] |
Jan 13, 2011IAT Task Conformance Task coverage –Can system do all tasks of interest? Task adequacy –Can user do tasks? –Does system match real-world tasks?
Jan 13, 2011IAT Task Analysis Analyzing how people do their jobs –Go to their environment –Learn about, analyze and describe their tasks Examine users’ tasks to better understand what they need from interface and how they will use it
Task Analysis Gather data about what users need to do or accomplish …then… Represent data for interpretation and use in design decisions Jan 13, 2011IAT 33454
Information to be Gathered Information about users Description of environment –where the tasks will be performed Major goals of the job –what will result in a successful end state? User preferences & needs –before they even start: coffee, pen, notebook, log sheets… Jan 13, 2011IAT 33455
Jan 13, 2011IAT Task Analysis Broad Focus Observe users of current system(s) Generate requirements –Hierarchical task analysis –Knowledge-based task analysis –Entity-Relationship model
Data Gathering Techniques 1. Observation 2. Interviews & Contextual Inquiry 3. Ethnography also… 4. Surveys & Questionnaires 5. Focus Groups & Expert Debriefing 6. Competitive Product Review 7. Documentation mining 8. Data logging Jan 13, 2011IAT 33457
Information to be Gathered Tasks & Subtasks: –Physical –Cognitive –Communication Conditions under which these tasks are done Results/outcomes of tasks Requirements to perform task: –Information –Communication with others –Equipment Jan 13, 2011IAT 33458
1. Observation Watch users do what they do –Typically from a distance Record with videotape –May require coding video later Take lots of notes, sketches Focus on specific task-relevant behaviors in notes, but later convert to abstract subtasks Jan 13, 2011IAT 33459
2. Interviews Engage the user more than just watching Structured interviews –Efficient, but requires training Unstructured –Inefficient, but requires no training Semi-structured –Good balance –Often appropriate Jan 13, 2011IAT 33460
3. Ethnography Deeply contextual inquiry –“Wallow in the data” “Live among” the users Understanding the full complexity of behavior, in its complete social context Note: Techniques based in sociology and anthropology--the study of humans Jan 13, 2011IAT 33461
4. Surveys & Questionnaires Subjective answers in a quantitative format –What does this mean? Questions: –Exploratory vs. confirmatory –Open-ended vs. categorical (exhaustive) –NB: If you ask it, use it. If you won’t/can’t use it, don’t ask it. Jan 13, 2011IAT 33462
5. Focus Groups Structured Interview with groups of individuals –3 to 10 persons –Use several different groups with different roles or perspectives –Manage the interaction Avoid few people dominating the discussion Focus on preferences and views, not performance Relatively low cost, quick way to learn a lot Audio or video record, with permission Jan 13, 2011IAT 33463
6. Competitive Products Looking for both good and bad ideas –Functionality –UI style Why are they successful or unsuccessful? What does successful really mean? –(Note: Successful does not equal usable) Jan 13, 2011IAT 33464
7. Document Mining Documentation –Often contains description of how the tasks should be done –Standards docs –Manuals –Histories –Best Practices Jan 13, 2011IAT 33465
8. Data Logging Automatically tracking: –Keystroke/mouse clicks –Timers –Logs of transactions –Physical location/movement trackers Cell phones GPS Jan 13, 2011IAT 33466
Now that you have observed… You have piles of notes, hours of video, surveys up to here… How can you digest and represent the data, to turn it into information? Jan 13, 2011IAT 33467
1. Task Outline Using a lawnmower to cut grass Step 1. Examine lawn a.Make sure grass is dry b.Look for objects laying in the grass Step 2. Inspect lawnmower a.Check components for tightness 1)Check that grass bag handle is securely fastened to the grass bag support 2)Make sure grass bag connector is securely fastened to bag adaptor 3)Make sure that deck cover is in place 4)Check for any loose parts (such as oil caps) 5)Check to make sure blade is attached securely b.Check engine oil level 1)Remove oil fill cap and dipstick 2)Wipe dipstick 3)Replace dipstick completely in lawnmower 4)Remove dipstick 5)Check that oil is past the level line on dipstick Jan 13, 2011IAT 33469
2. Narratives Describe tasks in sentences Often expanded version of task outline More effective for communicating general idea of task Not effective for details Not effective for branching tasks Not effective for parallel tasks Jan 13, 2011IAT 33470
3. Hierarchies & Networks Hierarchical Task Analysis (HTA) –Graphical notation & decomposition of tasks –Tasks as sets of actions –Tasks organized into plans (describes sequence) Network / Entity-Relationship Diagrams –Objects/people with links to related objects –Links described functionally and in terms of strength Jan 13, 2011IAT 33471
4. Flow Charts Flow Chart of Task Steps –Combines Entity-relationship (network) with sequential flow, branching, parallel tasks. –Includes actions, decisions, logic, by all elements of the system –Abstracted –Mature, well-known, good tools Jan 13, 2011IAT 33472
Jan 13, 2011IAT Knowledge-based Analysis List all objects and actions involved in a task, then build a taxonomy of them Often times, work with domain expert to get help
Summary: Data Gathering Techniques 1. Observation 2. Interviews & Contextual Inquiry 3. Ethnography also… 4. Surveys & Questionnaires 5. Focus Groups & Expert Debriefing 6. Competitive Product Review 7. Documentation mining 8. Data logging Jan 13, 2011IAT 33474
Jan 20, 2011IAT UI Design Principles Categories –Learnability support for learning for users of all levels –Flexibility support for multiple ways of doing tasks –Robustness support for recovery Always think about exceptions, suitability
Jan 20, 2011IAT Predictability I think that this action will do… Operation visibility - can see avail actions –e.g. menus vs. command shell –grayed menu items
Jan 20, 2011IAT Synthesizability From the resulting system state, My previous action did… –compare in command prompt vs UI –same feedback needed for all users, all apps?
Jan 20, 2011IAT Familiarity Does UI task relate real-world task or domain knowledge? –to anything user is familiar with? –Use of metaphors pitfalls –Are there limitations on familiarity?
Jan 20, 2011IAT Generalizability Does knowledge of one UI apply to others? –Cut and paste in many apps Does knowledge of one aspect of a UI apply to rest of the UI? –File browsers in MacOS/ Windows Aid: UI Developers guidelines
Jan 20, 2011IAT Consistency Similar ways of doing tasks –interacting –output –screen layout Is this always desirable for all systems, all users?
Jan 20, 2011IAT Dialog Initiative System pre-emptive –system does all prompts, user responds sometimes necessary Eg. Bank machine User pre-emptive –user initiates actions more flexible
Jan 20, 2011IAT Multithreading Two types –Concurrent input to multiple tasks simultaneously –Interleaved many tasks, but input to one task at a time
Jan 20, 2011IAT Task migratability Ability to move performance of task to entity (machine or person) that can do it better –Eg. Autopilot –Spellchecking –When is this good? Bad?
Jan 20, 2011IAT Substitutivity Flexibility in details of operations –Allow user to choose suitable interaction methods –Allow different ways to perform actions specify data configure –Allow different ways of presenting output to suit task, user
Jan 20, 2011IAT Customizability Ability to modify interface –By user - adaptability –By system - adaptivity
Jan 20, 2011IAT Observability Can user determine internal state of system from observable state? –Browsability explore current state (without changing it) –Reachability navigate through observable states –Persistence how long does observable state persist?
Jan 20, 2011IAT Recoverability Ability to continue to a goal after recognizing error Difficulty of Recovery procedure should relate to difficulty of original task –Forward Recoverability ability to fix when we can’t undo? –Backward Recoverability undo previous error(s)
Jan 20, 2011IAT Responsiveness Rate of communication between user and system –Response time time for system to respond in some way to user action(s) –Stability principle response time, rate should be consistent –As computers have gotten better, required computer response has gotten shorter
Jan 20, 2011IAT Task Conformance Task coverage –can system do all tasks of interest? Task adequacy –Can user do tasks? –Does system match real-world tasks?
Feb 3, 2011IAT IAT 334 Interface Design User Centered Design Metaphor Models Practice ______________________________________________________________________________________ SCHOOL OF INTERACTIVE ARTS + TECHNOLOGY [SIAT] |
Feb 3, 2011IAT Agenda User Centered Design -- Overall Process Design –Metaphors –Mental Models –Idea generation Design principles Displaying your designs –Storyboards –Lo-Fi –Wizard of Oz –Visual Basic, Flash, etc
Feb 3, 2011IAT User-Centered Design User-centered design process –Analysis of user needs –Prototype –Informal feedback –Iterate on design –Final application –Formal feedback
Feb 3, 2011IAT Analysis of User Needs Techniques: –Surveys –Card-sorting tasks –Interviews –Focus groups Look at competing products –Ethnography Participant observation
Feb 3, 2011IAT Prototyping Storyboards Paper simulations of application Wizard of Oz experiment Prototyping tools Cheap!
Feb 3, 2011IAT Informal Feedback Present prototype to users Do a quick questionnaire Observe the user struggle with your lousy design
Feb 3, 2011IAT Iterate on Design Redesign system –in light of initial user impressions –pay attention to common complaints Be prepared to abandon bad ideas!! It’s just an idea, not a measure of your worth!
Feb 3, 2011IAT Idea Creation Ideas come from –Imagination –Analogy –Observation of current practice –Observation of current systems Borrow from other fields –Animation –Theatre –Information displays –Architecture –... How do we create and develop new interface ideas and designs?
Feb 3, 2011IAT Interface Metaphors Metaphor - Application of name or descriptive term to another object which is not literally applicable –Use: Natural transfer - apply existing knowledge to new, abstract tasks –Problem: May introduce incorrect mental model
Feb 3, 2011IAT Mental Models What models of the world are the users using? Two Classes: Functional model –“Press the accelerator once, then turn the key” Structural model –OK, why do we do that?
Feb 3, 2011IAT Another example... Functional model –“Go north on King George, Cross the Pattullo, Turn left at 10 th Ave, Turn right at Kingsway, go 4.5km” Structural model –What location??
Feb 3, 2011IAT Idea Creation Methods for creating and developing interface ideas –Turn off your natural critique mechanism! –?
Feb 3, 2011IAT Idea Creation Methods 1. Consider new use for object 2. Adapt object to be like something else 3. Modify object for a new purpose
Feb 3, 2011IAT Idea Creation Methods 4. Magnify - add to object 5. Minimize - subtract from object 6. Substitute something similar
Feb 3, 2011IAT Idea Creation Methods 7. Rearrange aspects of object 8. Change the point of view 9. Combine data into an ensemble
Feb 3, 2011IAT Guidelines for Design 1. Provide a good conceptual model –User has mental model of how things work –Build design that allows user to predict effects of actions 2. Make things visible –Visible affordances, mappings, constraints –Remind person of what can be done and how to do it
Feb 3, 2011IAT Design Principles 1. Use simple and natural dialog in user’s language –Match user’s task in a natural way –Avoid jargon, techno-speak –Present exactly info that user needs Less is more!
Feb 3, 2011IAT Design Principles Here are 10 more detailed principles to follow about what to design and why
Feb 3, 2011IAT Design Principles 2. Strive for consistency –Sequences, actions, commands, layout, terminology –Makes more predictable –Dialog boxes all having same “closure” options
Feb 3, 2011IAT Design Principles 3. Provide informative feedback –Continuously inform user about what is occurring –Most important on frequent, substantive actions % in file –How to deal with delays? Special cursors % Done graphs
Feb 3, 2011IAT Design Principles 4. Minimize user’s memory load –Recognition is better than recall Make visible! –Describe required input format, include example and default Date: _ _ - _ _ - _ _ (DD-MM-YY) –Use small # of generally applicable cmds
Feb 3, 2011IAT Design Principles 5. Permit easy reversal of actions –Undo! –Reduces anxiety, encourages experimentation
Feb 3, 2011IAT Design Principles 6. Provide clearly marked exits –Don’t want the user to feel trapped –Examples Cancel button on dialogs Quit any time Interrupt/resume on lengthy operations
Feb 3, 2011IAT Design Principles 7. Provide shortcuts –Enable frequent users to perform often-used operations quickly Keyboard & mouse –Abbreviations –Menu shortcuts –Function keys –Command completion –Double click vs. menu selection Navigation between windows/forms Reuse –Provide a history system
Feb 3, 2011IAT Design Principles 8. Support internal locus of control –Put user in charge, not computer –Can be major source of anxiety
Feb 3, 2011IAT Design Principles 9. Handle errors smoothly and positively –“That Filename already exists” vs. –“Rename failed” 10. Provide useful help and documentation
Dialog Design Categories of Dialogs
Feb 10, 2011IAT Agenda Dialog design –Command Language –WIMP - Window, Icon, Menu, Pointer –Direct manipulation –Speech/Natural language –Gesture, pen, multi-touch, VR…
Feb 10, 2011IAT Command Languages Earliest UI interaction paradigms Examples –MS-DOS shell –UNIX shell
Feb 10, 2011IAT CL Attributes Work primarily by recall, not recognition Heavy memory load Little or nothing is visible so… Poor choice for novices but...
Feb 10, 2011IAT CL Attributes Specify commands to operate on current data collection User only controls initiation Single thread of control Some other display area needed
Feb 10, 2011IAT CL Design Goals Consistency –Syntax, order Good naming and abbreviations Doing your homework in design can help alleviate some of the negatives
Feb 10, 2011IAT Consistency Provide a consistent syntax –In general: Have options and arguments expressed the same way everywhere –UNIX fails here because commands were developed by lots of different people at different organizations No guidelines provided
Feb 10, 2011IAT Dialog Order English: SVO subject verb object CL: S assumed (you) Is VO or OV better? % rm file % file rm V dO iO vs. V iO dO % print file thePrinter % lpr -PthePrinter file
Dialog Order Technical issues dictate the choice: V iO dO % lpr -PthePrinter file The command must parse the arguments –So the command comes first Flags control how to act on the file –Want to parse all flags before checking files –e.g. -o outputFile Feb 10, 2011IAT
Feb 10, 2011IAT Syntax Pick a consistent syntax strategy –Simple command list eg., vi minimize keystrokes –Commands plus arguments realistic, can provide keyword parameters % cp from=foo to=bar –Commands plus options plus arguments what you usually see
Feb 10, 2011IAT Terminology Keep terminology consistent –Same concept expressed with same options –Useful to provide symmetric (congruent) pairings forward/backward next/prev control/meta
Feb 10, 2011IAT WIMP Focus: Menus, Buttons, Forms Predominant interface paradigm now (with some direct manipulation added) Advantages: –?
Recognition Recognition is easier than recall! –Recall has one cue –Recognition has the recall cue + the presence of the prompting word/icon Feb 10, 2011IAT
Feb 10, 2011IAT Menus Key advantages: –1 keystroke or mouse operation vs. many –No memorization of commands –Limited input set
Feb 10, 2011IAT Menus Many different types –pop-up –pull-down –radio buttons –pie buttons –hierarchies
Feb 10, 2011IAT Menu Items Organization strategies –Create groups of logically similar items –Cover all possibilities –Ensure that items are non-overlapping –Keep wording concise, understandable
Feb 10, 2011IAT Presentation Sequence Use natural if available –Time e.g. Breakfast, Lunch, Dinner –Numeric ordering e.g. Point sizes for font –Size Canada-> BC -> Surrey
Feb 10, 2011IAT Presentation Sequence Choices –Alphabetical –Group related items –Frequently used first –Most important first –Conventional order (MTWRF) Don’t change the order on the fly!
Feb 10, 2011IAT Direct Manipulation Continuous visibility of the objects and actions of interest Rapid, incremental actions Reversibility of all actions to encourage experimentation Syntactic correctness of all actions—every action is syntactically legal Replacement of command language syntax by direct manipulation of object of interest
Feb 10, 2011IAT Direct Manipulation Examples –WYSIWYG editors and word processors –VISICALC - 1 st electronic spreadsheet –CAD –Desktop metaphor –Video games
DM Syntax Typical DM syntax is postfix DirectObjects first, Verb second –In this case, the command completes the utterance Enables separate selection syntax Indirect objects typically specified before direct objects –e.g. brush size before painting in Photoshop Feb 10, 2011IAT
Feb 10, 2011IAT DM Essence Representation of reality that can be manipulated The user is able to apply intellect directly to the task Don’t have to name things, just touch them The tool itself seems to disappear
Direct Manipulation is Locality DM Relies on a primary geometric organization Items located nearby are frequently edited together –The words in a sentence –A column of numbers in a spreadsheet Less related -> Less local -> Less DM! Feb 10, 2011IAT
User Modeling Predicting thoughts and actions GOMS
Feb 24, 2011IAT Agenda User modeling –Fitt’s Law –GOMS
Feb 24, 2011IAT User Modeling Idea: If we can build a model of how a user works, then we can predict how s/he will interact with the interface –Predictive modeling Many different modeling techniques exist
User Modeling – 2 types Stimulus-Response –Hick’s law –Practice law –Fitt’s law Cognitive – human as interperter/predictor – based on Model Human Processor (MHP) –Key-stroke Level Model Low-level, simple –GOMS (and similar) Models Higher-level (Goals, Operations, Methods, Selections) Not discussed here Feb 24, 2011IAT
Power Law of Practice T n = T 1 n -a –T n to complete the nth trial is T 1 on the first trial times n to the power -a; a is about.4, between.2 and.6 –Skilled behavior - Stimulus-Response and routine cognitive actions Typing speed improvement Learning to use mouse Pushing buttons in response to stimuli NOT learning Feb 24, 2011IAT
Hick’s Law Decision time to choose among n equally likely alternatives –T = I c log 2 (n+1) –I c ~ 150 msec Feb 24, 2011IAT
Fitts’ Law Models movement times for selection (reaching) tasks in one dimension Basic idea: Movement time for a selection task –Increases as distance to target increases –Decreases as size of target increases Feb 24, 2011IAT
Fitts: Index of Difficulty ID - Index of difficulty ID is an information theoretic quantity –Based on work of Shannon – larger target => more information (less uncertainty) Feb 24, 2011IAT ID = log 2 (d/w + 1.0) bits result width (tolerance) of target distance to move
Design implications Menu item size Icon size Put frequenlty used icons together Scroll bar target size and placement –Up / down scroll arrows together or at top and bottom of scroll bar Feb 24, 2011IAT
Feb 24, 2011IAT GOMS One of the most widely known Assumptions –Know sequence of operations for a task –Expert will be carrying them out Goals, Operators, Methods, Selection Rules
Feb 24, 2011IAT GOMS Procedure Walk through sequence of steps Assign each an approximate time duration -> Know overall performance time (Can be tedious)
Feb 24, 2011IAT Limitations GOMS is not for –Tasks where steps are not well understood –Inexperienced users Why? Good example: Move a sentence in a document to previous paragraph
Feb 24, 2011IAT Goal End state trying to achieve Then decompose into subgoals Moved sentence Select sentence Cut sentence Paste sentence Move to new spot Place it
Feb 24, 2011IAT Operators Basic actions available for performing a task (lowest level actions) Examples: move mouse pointer, drag, press key, read dialog box, …
Feb 24, 2011IAT Methods Sequence of operators (procedures) for accomplishing a goal (may be multiple) Example: Select sentence –Move mouse pointer to first word –Depress button –Drag to last word –Release
Feb 24, 2011IAT Selection Rules Invoked when there is a choice of a method Example: Could cut sentence either by menu pulldown or by ctrl-x
Feb 24, 2011IAT Further Analysis GOMS is often combined with a keystroke level analysis –Assigns times to different operators –Plus: Rules for adding M’s (mental preparations) in certain spots
Feb 24, 2011IAT Example 1. Select sentence Reach for mouseH0.40 Point to first wordP1.10 Click button downK0.60 Drag to last wordP1.20 ReleaseK secs 2. Cut sentence Press, hold ^Point to menu Press and release ‘x’orPress and hold mouse Release ^Move to “cut” Release Move Sentence
Keystroke-Level Model Simplified GOMS KSLM - developed by Card, Moran & Newell, see their book –The Psychology of Human-Computer Interaction, Card, Moran and Newell, Erlbaum, 1983 Skilled users performing routine tasks Assigns times to basic human operations - experimentally verified Based on MHP - Model Human Processor Feb 24, 2011IAT
Feb 24, 2011IAT User Profiles Attributes: –attitude, motivation, reading level, typing skill, education, system experience, task experience, computer literacy, frequency of use, training, color-blindness, handedness, gender,… Novice, intermediate, expert
Feb 24, 2011IAT Motivation User –Low motivation, discretionary use –Low motivation, mandatory –High motivation, due to fear –High motivation, due to interest Design goal –Ease of learning –Control, power –Ease of learning, robustness, control –Power, ease of use
Feb 24, 2011IAT Knowledge & Experience Experience tasksystem –lowlow –highhigh –lowhigh –highlow Design goals –Many syntactic and semantic prompts –Efficient commands, concise syntax –Semantic help facilities –Lots of syntactic prompting
Feb 24, 2011IAT Job & Task Implications Frequency of use –High - Ease of use –Low - Ease of learning & remembering Task implications –High - Ease of use –Low - Ease of learning System use –Mandatory - Ease of using –Discretionary - Ease of learning
Feb 24, 2011IAT Modeling Problems 1. Terminology - example –High frequency use experts - cmd language –Infrequent novices - menus What’s “frequent”, “novice”?
Feb 24, 2011IAT Modeling Problems (contd.) 2. Dependent on “grain of analysis” employed –Can break down getting a cup of coffee into 7, 20, or 50 tasks –That affects number of rules and their types
Feb 24, 2011IAT Modeling Problems (contd.) 3. Does not involve user per se –Don’t inform designer of what user wants 4. Time-consuming and lengthy