Design of Everyday Things

Don Norman on Design & HCI

Today’s agenda

Project scores Poster 8400 topics Design of everyday things Midterm review Next week:

6:30-7:30: web design 7:45-9:15: Midterm

Poster

March 12 (first class after spring break) Present (at least) 3 design possibilities, get

feedback Organization:

General topic, perhaps scenario, users, requirements, etc.

At least 3 DIFFERENT designs – sketches, storyboards, perhaps descriptions or features

You can bring whatever else you have Materials: whatever you like

Summary

Darn these hooves!I hit the wrong switch again!Who designs these instrumentPanels, raccoon?!

Don Norman

Professor at Northwestern and Principal of Nielsen Norman group

Previously Professor at UCSD, senior positions at Apple & HP

ACM/CHI Lifetime Achievement Award

Prolific author http://www.jnd.org/

Discussion

What did you take away from DOET book so far?

Here are some

Affordances are important Minimize the gulf of interpretation and gulf of

execution Use natural mappings Make state visible Use a conceptual model that makes sense Provide feedback

Daily Challenges

How many of you can use all the functionality in your VCR Digital watch Copy machine Stereo system Plumbing fixtures

Hall of Shame Example

Leitz slide projector To move forward, short press To move backward, long press

What happens when you get frustrated?

Changing Ringer Volume

Press “Program” Press “6” Set volume

Low - Press “1” Medium - Press “2” High - Press “3”

Press “Program”

Much better…

Important Concepts

Affordances Visibility Conceptual models Mapping Feedback Constraints

Affordances

Perceived and actual properties of an object that determine how it could be used Chair is for sitting Button is for pushing Door handle is for …. Scroll arrow is for … Icon is for …

Affordances

Affordances

Door Opening Affordances

1 2 3 4 5

6 7

Which doors are easy to open?

Which doors are hard to open?

Why?

Affordances in interfaces

Interfaces are virtual and do not have ‘real’ affordances like physical objects

Interfaces have ‘perceived’ affordances Learned conventions of arbitrary

mappings between action and effect at the interface

Some mappings are better than others

Mantra

Complex things may need explanation, but simple things should not If a simple thing requires instructions, it is

likely a failed design

Norman’s 2 main principles Provide a good conceptual model Make things visible

Affordances is part of this

Conceptual Models

People build their own systems of how things work Example - thermostat

Designer can help user foster an appropriate conceptual model Appearance, instructions, behavior...

Conceptual Models

Mental models are not always right Two Classes:

Functional model Stimulus - response “Press the accelerator once, then turn the key” At surface or superficial level

Structural model Deeper sense of why it happens, not just what

happens “Press the accelerator to engage the automatic choke

on a carburetor”

Visibility

When functionality is hidden, problems in use occur Occurs when number of functions is greater

than number of controls When capabilities are visible, it does not

require memory of how to use Recognition over Recall in the world vs. in the head

Simple Example

Bathroom faucets Two functions

Hot/cold Flow

Bathroom Faucets 1

Can you figureout how to useit?

Are two functionsclear and independent?

Bathroom Faucets 2

Can you figureout how to useit?

Are two functionsclear and independent?

Bathroom Faucets 3

Can you figureout how to useit?

Are two functionsclear and independent?

My parent’s microwave

5:45

My microwave

Which is Faster for Setting Time?

Mapping

Relationship between control and action/result in the world

Take advantage of physical analogies or cultural understandings Good:

Car, various driving controls Mercedes Benz seat adjustment example

Bad Car stereo - Knob for front/back speakers

Which is better?

or

Mapping Example: Euros

Size::value

Mapping Example: Stove

Which controls which?

Why not this?

Yikes!

Why Not Design Better

Stove

Speakers

Physical, monetary,convenience, etc.,constraints dictateotherwise

Feedback

Sending information back to the user about what has been done

Includes sound, highlighting, animation and combinations of these

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

“ccclichhk”

What’s wrongwith this picture?

Constraints

Limitations on what can be done Physical - keys Semantic - menu graying Cultural - Colors Logical - When all above don’t apply

Simple Example

What if both sides were “big” and you had toremember which side the “small” one went into?

Electric plugs

Knowledge in Head vs. Knowledge in the World

Head Not easy to retrieve Learning required, good

conceptual model makes easier

Can be very efficient Not easy first time Aesthetics do not need to

make info visible

World Easy to retrieve No learning, only

interpretation Use slowed by need to

find the info to interpret Easy for first time Can be cluttered or

inelegant

Execution-Evaluation cycle

Norman (DOET, p. 46)

UserGoals

PhysicalSystem

Gulfof

Execution

Gulfof

Evaluation

Goals, Execution, Evaluation

Physical System

GoalsWhat we

want to happen

ExecutionWhat we

do to the world

EvaluationComparing what happened

with what we wanted to happen

(Gulf of Execution) (Gulf of Evaluation)

Execution

GoalsWhat we

want to happen

An intention to actso as to achieve the goal

The actual sequence of actionsthat we plan to do

The physical execution of that action sequence

Physical System

Evaluation

GoalsWhat we

want to happen

Evaluation of the interpretationswith what we expected to happen

Interpreting the perception accordingto our expectations

Perceiving the stateof the world

Physical System

Seven Stages - All Together

GoalsWhat we

want to happen

Evaluation of the interpretationswith what we expected to happen

Interpreting the perception accordingto our expectations

Perceiving the stateof the world

An intention to actso as to achieve the goal

The actual sequence of actionsthat we plan to do

The physical execution of that action sequence

Physical System

Implications – Which Gulf does these Address?

Make current state and action alternatives visible

Need good conceptual model with consistent system image

Interface should include mappings that reveal relationships between stages

User should receive continuous feedback Provide affordances

Goal: Minimize Gulfs

Gulf of Execution Conceptual model Affordances Natural mappings

Gulf of Evaluation Make state visible Feedback

Errors - Three Considerations

Avoiding and preventing Identifying and understanding Handling and recovering

Why errors are important

Errors are unavoidableTo err is humanMaking mistakes is part of learning

Designer’s responsibilityUnderstand why errors occurMinimize likelihoodAllow for recognition of error and graceful

recovery (forward or backward)

Example Studies – Errors Happen! 170 experienced UNIX users over 9 days

Individual commands had error rates of 3-50%

300 security system users over 20 months 12,117 error messages Most common 11 errors -> 65% 2517 involved repeated errors (with no non-errors in

between) within 10 minutes Bad error recovery/help

Kraut et al, CHI ‘83

Mosteller & Ballas, Human Factors ‘89

User-Computer Dialog

Three phases Read-scan phase -- Perceptual errors Think phase -- Cognitive errors Respond phase -- Motor errors

Perceptual Errors

Result from insufficient or poor perceptual cues Display of objects that are visually similar Invisible or poorly expressed states Failure to capture user’s attention Lack of perceivable feedback

Cognitive Errors

Caused by taxing the memory and problem solving capabilities Tax recall memory Lack of or poor mnemonic aids Inconsistency Lack of context or status info

e.g., where came from in a menu Mental calculations and translations

Motor Errors

Taxing the eye-hand coordination and motor skills Awkward motor movements Highly similar motor sequences

e.g., double click, click Pressure for speed Require a high degree of hand-eye

coordination Requiring special types of motor skills (type)

Mistakes and Slips

Mistakes (hopefully avoidable) Wrong intention Incorrect mental model Novice behavior

Slips (unavoidable) Wrong execution Skilled behavior

Moral …

… slips happen

Types of Slips

1. Capture error - Continue frequently done activity instead of intended one (similar starts) Confirm deletion of file instead of cancel

2. Description error - Intended action has much in common with others possible (usually when distracted, close proximity) shift key & caps lock key

Types of Slips

3. Data driven error - Triggered by arrival of sensory info which intrudes into normal action Call to give someone a number, dial that

number instead 4. Associative activation - Internal thoughts

and associations trigger action Phone rings, yell “come in”

Types of Slips

5. Loss of activation - Forgetting goal in middle of sequence of actions Start going into room, then forget why you’re

going there 6. Mode errors - Do action in one mode

thinking you’re in another Delete file, but you’re in wrong directory Scroll wheel in PowerPoint

What to do?

As much as possible Prevent mistakes Allow recovery from slips

Error Prevention Guidelines

Eliminate modes or provide visible cues for modes - no invisible modes

Use consistent representation (color, style) Maximize recognition, minimize recall Design non-similar motor sequences for commands Minimize need for typing Test and monitor for errors and engineer them out Allow reconsideration of action by user (e.g., removing file from

trash) Avoid ambiguous and unclear prompts and messages - as in

next set of examples!

Great Examples

Error Recovery Guidelines

Provide appropriate type of response Gag - Prevent user from continuing

Erroneous login Warn - Warn user an unusual situation is occurring

Bell or alert box Nothing - Don’t do anything (Careful, user must

determine problem) move file to bad place

Self-correct - Guess correct action & do it Spell-check correction

Dialog - System opens dialog with user Go into debugger on run-time crash

Error Recovery Guidelines

Provide undo function Provide cancel function from operations in

progress Require confirmation for drastic, destructive

commands Provide reasonableness checks on input data

Did you really mean to order 5000? Return cursor to error field, allow fix Provide some intelligence

Guess what they wanted to do Provide quick access to context-sensitive help

Error Message - What to Say

Error: Error code -37 Description: Disk full Prescription: Disk full; recover disk

space Prescription + aid: Disk full; recover space

by deleting files or defragmenting

Prescription + offer: Disk full; proceed with disk defragmentation? Otherwise delete files.

How Does This Example Fit In?

Error Message Wording - Vocabulary Problem with previous example - some users

will not know what defragmentation means!! Vocabulary

User-oriented Defined in advance for commonality

throughout all messages (in style guide) Alternatives to defragmentation ?

Error Message Wording - Tone

Sorry, command not recognized Command not recognized :-( Command not recognized Command not recognized!!

Implications for design

Scenarios should include errors !!! Distinguish between skilled and learner errors Uncover errors in the existing system

how do people self-monitor (cheat sheets)

Midterm review

How to study: Look at slides for topics, bullets, vocabulary,

etc. Find details and examples in the books as

needed Test format

25-50% true/false, multiple choice, fill-in-blank Rest short answer, probably with one longer

answer

Review

What is usability? What is design? Why is it hard? The user centered design process

General steps various models – high level understanding Waterfall vs. other models

Ethics What concerns in working with people?

History What’s a paradigm? What were the major paradigm shifts? What were the

impacts to HCI/users?

Requirements Review

Functional vs. non functional Summative eval vs. formative eval What pieces are part of this?

User characteristics, task analysis, environment, etc.etc. Persona – what is it and what makes a good one? Scenario – what is it and what makes a good one? Stakeholders

How do you gather data? Tradeoffs? Interview, questionnaire, observation, etc. etc. Contextual Inquiry – what is it, why, tradeoffs…

Task models Hierarchical task analysis - how to do it? Other models – what can they represent?

Humans review

What are issues concerning our senses? What are difficulties or disabilities that could occur? Model Human Processor model of memory

What’s a chunk? Why do we care? What are implications? (recognition over recall, etc.)

Other processes – what are they? (attention, learning) What are the implications?

Other models of human cognition Situation action Activity theory Distributed cognition Basic understanding, Compare/contrast each

Interaction Review

Command line WIMP Direction manipulation Pen & mobile Speech & natural language

Issues, advantages, disadvantages, etc.

Design

Prototyping What’s vertical vs. horizontal? What’s low vs. high fidelity? What are various methods?

Scenarios, mockups/sketches, etc. Wizard of Oz Issues and tradeoffs?

Visual Design Form follows function Graphic design principles?

Clarity, proximity, alignment, etc.

DOET Review

What are Norman’s principles? Affordance, mapping, feedback, etc. What are they? Why needed?

Execution-evaluation cycle Steps of cycle, what helps reduce gulfs?

Errors Perceptual, cognitive, motor Mistake vs. slip

Error prevention and recovery guidelines