Introduction to Human-Computer InteractionIntroduction to Human-Computer Interaction SMD157...

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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


Overview

• What is HCI?

• Motivation for study

• User-centered design

• A little cognitive & perceptual psychology




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


A Definition of Usability

… the effectiveness, efficiency, and satisfaction with which specified users can achieve specified goals in particular environments …

ISO DIS 9241-11


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




Motivation


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


An Annoying User Interface: the Old German RailSchedule

• A solution is to addan example.

• However, atemplate(DD.MM.YY)removesambiguity.


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 ⇓


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.


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.


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?




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


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


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


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


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.


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




Very Basic Cognitive Psychology

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The Human Information Processing System

• Perceptual System

• Memory System- Perceptual- Working

- Long term

• Motor Control System


The Sensory System

• Sight- Primary communication channel.

• Hearing- Mostly used for warning signals.

• Touch- Keyboard and button feedback.

• Smell, Taste- Not used by computers.


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.


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!


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.


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.


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?


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


Questions?

Introduction to Human-Computer InteractionIntroduction to Human-Computer Interaction SMD157...

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