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Oct-27-05 SMD157, Introduction to HCI 1 L
INSTITUTIONEN FÖRSYSTEMTEKNIK
LULEÅ TEKNISKA UNIVERSITET
Introduction to Human-Computer Interaction
SMD157
Human-Computer Interaction
Fall 2005
Oct-27-05 SMD157, Introduction to HCI 2 L
Overview
• What is HCI?
• Motivation for study
• User-centered design
• A little cognitive & perceptual psychology
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INSTITUTIONEN FÖRSYSTEMTEKNIK
LULEÅ TEKNISKA UNIVERSITET
What is Human-Computer Interaction?
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Human-Computer Interaction
• Study of:- Design,- Evaluation &- Implementation of
+ Interactive computing systems
• Concerns:- Use by humans- For a purpose- Within an organization or group
• Goal ⇒ Usable Systems
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A Definition of Usability
… the effectiveness, efficiency, and satisfaction with which specified users can achieve specified goals in particular environments …
ISO DIS 9241-11
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Meaning of the Definition
• Goals- Effectiveness
- Efficiency
- Satisfaction
• Limits- Specified users- Specified goals
- Particular environments
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HCI is Multi-Disciplinary
Psychology Sociology
ArtDesign
Engineering
ComputerScience
Philosophy Linguistics
Physiology
AnthropologyErgonomics
A. I.
Understandingthe user
UserModelsHelp
GroupWork
Aesthetics LayoutFaster machines,Faster systems,Means for better
interfaces
Commandlanguages
Consistency
Physicalcapabilities
Equipment design
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INSTITUTIONEN FÖRSYSTEMTEKNIK
LULEÅ TEKNISKA UNIVERSITET
Motivation
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Why Study Human-Computer Interaction?
• Over 95% of all new software systems contain a userinterface.
• User interface development uses between 25% and50% percent of development resources.
• A bad user-interface can be annoying, embarrassing,and even deadly.
• A good user interface can earn a company billions.
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An Annoying User Interface: the Old German RailSchedule
• The date field in theEnglish query form is inGerman format(dd.mm.yy)
• Problem: native speakersusually use the wrongformat
• Results:- Users are annoyed when
they have to type the datein again
- The system often has toprocess two queries
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An Annoying User Interface: the Old German RailSchedule
• A solution is to addan example.
• However, atemplate(DD.MM.YY)removesambiguity.
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Another Annoying Interface:the old “Hitta rätt postnummer”
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What’s Wrong?
• Result of query with street number ⇓
• Result of query taking away the number ⇓
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An Embarrassing User Interface: an Old TextEditor
• The editor used “,” to select the current line and “.” to select theentire document.
• Problem: the keys are too close together and can be easilyswitched.
• Result:- A British election document was edited with this editor.- The word “poll” in the sentence “A heavy poll is expected.” was to be
changed to “turnout”.- The operator typed “.” instead of “,”- This was unfortunate for a candidate named Pollack.- The embarrassing result was blamed on the computer not the user
interface.
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A Deadly User Interface: The Fire Control System on theUSS Vincennes
• Altitude for tracked aircraft on the Vincennes’s combatcontrol system:- Not shown on its central big screen display
- Had to be read off of an auxiliary display
• Problem:- Altitude is a key piece of information when judging aircraft
intention
- Information on separate screens can easily be misinterpreted,especially under stress
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A Deadly User Interface: The Fire Control System on theUSS Vincennes
• Result:- An Iran Air airliner was confused with an F14 and report
to be diving to 9000 feet.- It was in fact level at 12500.
- The airliner was shot down and 290 people died.- Other ships with less advanced systems but better
designed interfaces knew the true facts, but wereunable to intervene in time.
• Concentrating on the “latest” technology withoutconsidering the operator is dangerous.
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A Profitable User Interface: The MacintoshDesktop
• Window-based user interfaces were pioneered at Xerox PARC.
• Apple adopted this style for the Lisa and then Macintoshsystems.
• The user interface fueled sales of the Mac
- PCs were much cheaper and somewhat faster- The company has earned billions on the Mac
• Today the only available user interfaces look a lot like a Mac.
• Why?
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INSTITUTIONEN FÖRSYSTEMTEKNIK
LULEÅ TEKNISKA UNIVERSITET
How Does One Build Good User Interfaces?
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Usability Oriented System Development
• Components- User studies
- Usability goals
+ Set as part of system requirements- Design with multiple alternatives
- Prototyping- Evaluation of the prototypes with respect to usability
- Iterative work to achieve the goals
• A.k.a, user-centered design
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User-Centered Design
• Know the users.
• Know their tasks.
• Design to fit the system to theusers and their tasks.
• Evaluate the design.
• Iterate until a good design isachieved.
} -----------> External Analysis
---> Design & Prototype
------------> Evaluate
------> Repeat cycle
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Iterative Development
Re-analyze
EvaluatePrototype
Analyze Goals Met
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External Analysis
• Goal is to identify and understand:- The target user group
- The work environment
- The required system services
• Methodologies- Observation- Interviews
- Analysis of competing products
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Balance of Automation and Human Control
• Ultimate goal: simplify user's task by eliminating actionswhen no judgment is required.
• Issues:- Real world is an open system- Computers constitute closed system- Human judgment necessary for unpredictable events
+ Unanticipated situations+ Equipment failure+ Improper human performance+ Incomplete or erroneous data
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Design & Prototype
• Create a design using:- Principles of interaction
- Graphics design principles
- Following guidelines
• Implement prototypes to:- Test the design- Choose between alternatives
- Minimize the cost of experimentation
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Evaluate
• Time to learn
• Speed of performance
• Rate of errors by users
• Retention over time
• Subjective satisfaction
⇒ N.B., these are things to set asusability requirements.
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Repeat Cycle
• No one gets it right the first time
• But, by repeating the analyze, (re-)design, implement,evaluate cycle one gets “close enough.
• “Close enough” is determined by:- Economics- Quality
- Customer (user) satisfaction
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INSTITUTIONEN FÖRSYSTEMTEKNIK
LULEÅ TEKNISKA UNIVERSITET
Very Basic Cognitive Psychology
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The Human Information Processing System
• Perceptual System
• Memory System- Perceptual- Working
- Long term
• Motor Control System
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The Sensory System
• Sight- Primary communication channel.
• Hearing- Mostly used for warning signals.
• Touch- Keyboard and button feedback.
• Smell, Taste- Not used by computers.
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Perception
• The Gestalt principles
• The visual system and attention
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Gestalt Principles
• Pragnanz:- Structure is
seen as simply as possible.
• Proximity:- Nearby objects tend to be
grouped.
• Similarity:- Similar items tend to be
grouped.
• Closure:- Nearby contours tend to be
united.
• Continuation:- Grouping tends to occur along
simple curves.
• Common fate:- Elements that move together
tend to be grouped.
• Familiarity:- The familiar or meaningful
tends to be grouped.
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The Visual System and Attention
• Logical and meaningful structure helps focus attention
• Motion immediately draws the user’s attention (Blinkingcounts as motion)
• Colors like red and yellow indicate danger and warningin A WESTERN SOCIETY.
• Some color combinations are hard to see.
Hard to focus!
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Colors and Culture
96%-BLUE Cold
-72%WHITE Cold
81%45%YELLOW Caution
61%99%
62%45%
GREEN SafeGo
95%90%100%
31%65%49%
RED HotDangerStop
AmericansHong Kong ChineseColor/Meaning
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Memory
• Divided into:- Sensory memory ⇒ buffers between the senses and the
mind- Working memory ⇒ scratch pad for things immediately
needed- Long-term memory ⇒ holds everything one knows
+ Knowledge stored as facts or associations+ Images
• Limited parallel capability among verbal, visual, andmotor tasks.
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Memory Limits
• Sensory memory is very limited.- Auditory memory, 2 second duration
- Visual memory, .5 second duration
• Short term or working memory- 7 ± 2 chunks, several second duration
- 1-2 things
• Long term memory- Essentially unlimited, but you have to find things.
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How Memory Affects HCI
• People forget long command names or sequences ofletters and digits.
• New stimuli push out old plans.
• In a hypertext (WWW page) people get “lost”. (Theycan’t remember the relationship between the currentpage and the others they’ve visited.)
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How the Motor Control System Affects HCI
• It’s easier to point at big things than little things.
• It’s easier to point at near things than far things.• Big and near interact.
• Big can be in one dimension.- Pointing here is harder than, here
Why is the Macintosh menu bar location superior?
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Summary
• HCI is the study of how to improve the design of user interfaces in order tosupport human activity.
• HCI is important- Computers are ubiquitous, most have an interface- Design is important for safety, usefulness, & profitability
• User-centered design- Know the users- Know their tasks- Iterate until it’s good enough
• Cognitive & perceptual psychology- Gestalt principles- Memory, perceptual, long-term, and limited working- Motor control, big and near is easier to point at
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Questions?