chapter 3

the interaction
The Interaction

• interaction models
– translations between user and system
• ergonomics
– physical characteristics of interaction
• interaction styles
– the nature of user/system dialog
• context
– social, organizational, motivational
What is interaction?

communication

user  system

but is that all … ?

– see “language and action” in chapter 4 …
Some terms of interaction

domain – the area of work under study

e.g. graphic design
goal – what you want to achieve
e.g. create a solid red triangle
task – how you go about doing it
– ultimately in terms of operations or actions
e.g. … select fill tool, click over triangle

Note …
– traditional interaction …
– use of terms differs a lot especially task/goal !!!
Donald Norman’s model

• Seven stages
– user establishes the goal
– formulates intention
– specifies actions at interface
– executes action
– perceives system state
– interprets system state
– evaluates system state with respect to goal

• Norman’s model concentrates on user’s view

of the interface
execution/evaluation loop
goal
execution evaluation
system
• user establishes the goal
• formulates intention
• specifies actions at interface
• executes action
• perceives system state
• interprets system state
• evaluates system state with respect to goal
execution/evaluation loop
goal
execution evaluation
system
• user establishes the goal
• formulates intention
• specifies actions at interface
• executes action
• perceives system state
• interprets system state
• evaluates system state with respect to goal
execution/evaluation loop
goal
execution evaluation
system
• user establishes the goal
• formulates intention
• specifies actions at interface
• executes action
• perceives system state
• interprets system state
• evaluates system state with respect to goal
execution/evaluation loop
goal
execution evaluation
system
• user establishes the goal
• formulates intention
• specifies actions at interface
• executes action
• perceives system state
• interprets system state
• evaluates system state with respect to goal
Using Norman’s model

Some systems are harder to use than others

Gulf of Execution
user’s formulation of actions
≠ actions allowed by the system

Gulf of Evaluation
user’s expectation of changed system state
≠ actual presentation of this state
 ergonomics

physical aspects of interfaces

industrial interfaces
Ergonomics

• Study of the physical characteristics of

interaction

• Also known as human factors – but this can

also be used to mean much of HCI!

• Ergonomics good at defining standards and

guidelines for constraining the way we design
certain aspects of systems
Ergonomics - examples

• arrangement of controls and displays

e.g. controls grouped according to function or
frequency of use, or sequentially
• surrounding environment
e.g. seating arrangements adaptable to cope with all
sizes of user
• health issues
e.g. physical position, environmental conditions
(temperature, humidity), lighting, noise,
• use of colour
e.g. use of red for warning, green for okay,
awareness of colour-blindness etc.
 interaction styles

dialogue … computer and user

distinct styles of interaction

Common interaction styles

• command line interface

• menus
• natural language
• question/answer and query dialogue
• form-fills and spreadsheets
• WIMP
• point and click
• three–dimensional interfaces
Command line interface

• Way of expressing instructions to the

computer directly
– function keys, single characters, short abbreviations,
whole words, or a combination

• suitable for repetitive tasks

• better for expert users than novices
• offers direct access to system functionality
• command names/abbreviations should be
meaningful!
Typical example: the Unix system
Menus

• Set of options displayed on the screen

• Options visible
– less recall - easier to use
– rely on recognition so names should be meaningful
• Selection by:
– numbers, letters, arrow keys, mouse
– combination (e.g. mouse plus accelerators)
• Often options hierarchically grouped
– sensible grouping is needed
• Restricted form of full WIMP system
Natural language

• Familiar to user
• speech recognition or typed natural language
• Problems
– vague
– ambiguous
– hard to do well!
• Solutions
– try to understand a subset
– pick on key words
Query interfaces

• Question/answer interfaces
– user led through interaction via series of questions
– suitable for novice users but restricted functionality
– often used in information systems

• Query languages (e.g. SQL)

– used to retrieve information from database
– requires understanding of database structure and
language syntax, hence requires some expertise
Form-fills

• Primarily for data entry or data retrieval

• Screen like paper form.
• Data put in relevant place
• Requires
– good design
– obvious correction
facilities
Spreadsheets

• first spreadsheet VISICALC, followed by

Lotus 1-2-3
MS Excel most common today
• sophisticated variation of form-filling.
– grid of cells contain a value or a formula
– formula can involve values of other cells
e.g. sum of all cells in this column
– user can enter and alter data spreadsheet
maintains consistency
WIMP Interface

Windows
Icons
Menus
Pointers
… or windows, icons, mice, and pull-down menus!

• default style for majority of interactive

computer systems, especially PCs and desktop
machines
Point and click interfaces

• used in ..
– multimedia
– web browsers
– hypertext

• just click something!

– icons, text links or location on map

• minimal typing
Three dimensional interfaces

• virtual reality
• ‘ordinary’ window systems
– highlighting flat buttons …
– visual affordance
– indiscriminate use click me!
just confusing!
• 3D workspaces … or sculptured
– use for extra virtual space
– light and occlusion give depth
– distance effects
elements of the wimp interface

windows, icons, menus, pointers

+++
buttons, toolbars,
palettes, dialog boxes
also see supplementary material
on choosing wimp elements
Windows

• Areas of the screen that behave as if they

were independent
– can contain text or graphics
– can be moved or resized
– can overlap and obscure each other, or can be laid
out next to one another (tiled)

• scrollbars
– allow the user to move the contents of the window
up and down or from side to side
• title bars
– describe the name of the window
Icons

• small picture or image

• represents some object in the interface
– often a window or action
• windows can be closed down (iconised)
– small representation fi many accessible
windows
• icons can be many and various
– highly stylized
– realistic representations.
Menus

• Choice of operations or services offered on the screen

• Required option selected with pointer

File Edit Options Font

Typewriter
Screen
Times

problem – take a lot of screen space

solution – pop-up: menu appears when needed
Pointers

• important component
– WIMP style relies on pointing and selecting things
• uses mouse, trackpad, joystick, trackball,
cursor keys or keyboard shortcuts
• wide variety of graphical images
Kinds of Menus

• Menu Bar at top of screen (normally), menu

drags down
– pull-down menu - mouse hold and drag down menu
– drop-down menu - mouse click reveals menu
– fall-down menus - mouse just moves over bar!

• Contextual menu appears where you are

– pop-up menus - actions for selected object
– pie menus - arranged in a circle
• easier to select item (larger target area)
• quicker (same distance to any option)
… but not widely used!
Menus extras

• Cascading menus
– hierarchical menu structure
– menu selection opens new menu
– and so in ad infinitum

• Keyboard accelerators
– key combinations - same effect as menu item
– two kinds
• active when menu open – usually first letter
• active when menu closed – usually Ctrl + letter
usually different !!!
Menus design issues

• which kind to use

• what to include in menus at all
• words to use (action or description)
• how to group items
• choice of keyboard accelerators
Buttons

• individual and isolated regions within a

display that can be selected to invoke
an action

• Special kinds
– radio buttons
– set of mutually exclusive choices
– check boxes
– set of non-exclusive choices
Toolbars

• long lines of icons …

… but what do they do?

• fast access to common actions

• often customizable:
– choose which toolbars to see
– choose what options are on it
Palettes and tear-off menus

• Problem
menu not there when you want it

• Solution
palettes – little windows of actions
– shown/hidden via menu option
e.g. available shapes in drawing package
tear-off and pin-up menus
– menu ‘tears off’ to become palette
Dialogue boxes

• information windows that pop up to

inform of an important event or request
information.

e.g: when saving a file, a dialogue box is

displayed to allow the user to specify the
filename and location. Once the file is
saved, the box disappears.
 interactivity

easy to focus on look

what about feel?
Speech–driven interfaces

• rapidly improving …
… but still inaccurate
• how to have robust dialogue?
… interaction of course!

e.g. airline reservation:

reliable “yes” and “no”
+ system reflects back its understanding
“you want a ticket from New York to Boston?”
Look and … feel

• WIMP systems have the same elements:

windows, icons., menus, pointers, buttons, etc.

• but different window systems

… behave differently
e.g. MacOS vs Windows menus

appearance + behaviour = look and feel

Initiative

• who has the initiative?

old question–answer – computer
WIMP interface – user

• WIMP exceptions …
pre-emptive parts of the interface

• modal dialog boxes

– come and won’t go away!
– good for errors, essential steps
– but use with care
Error and repair

can’t always avoid errors …

… but we can put them right

make it easy to detect errors

… then the user can repair them
hello, this is the Go Faster booking system
what would you like?
(user) I want to fly from New York to London
you want a ticket from New York to Boston
(user) no
sorry, please confirm one at a time
do you want to fly from New York
(user) yes
………
Context

Interaction affected by social and organizational

context

• other people
– desire to impress, competition, fear of failure
• motivation
– fear, allegiance, ambition, self-satisfaction
• inadequate systems
– cause frustration and lack of motivation
Experience, engagement and fun

designing experience
physical engagement
managing value
Experience?
• home, entertainment, shopping
– not enough that people can use a system
– they must want to use it!

• psychology of experience
– flow (Csikszentimihalyi)
– balance between anxiety and boredom

• education
– zone of proximal development
– things you can just do with help

• wider ...
– literary analysis, film studies, drama
Designing experience

• real crackers
– cheap and cheerful!
– bad joke, plastic toy, paper hat
– pull and bang
Designing experience

• virtual crackers
– cheap and cheerful
– bad joke, web toy, cut-out mask
– click and bang
Designing experience

• virtual crackers
– cheap and cheerful
– bad joke, web toy, cut-out mask
– click and bang
how crackers work
fill in web form

sender receive email recipient

To: wxv
From: ..

closed
cracker page

open
watches recipient clicks
message
progress cracker opens ...
very slowly
open
cracker page
sender joke
links

web toy
mask
Physical design

• many constraints:
– ergonomic – minimum button size
– physical – high-voltage switches are big
– legal and safety – high cooker controls
– context and environment – easy to clean
– aesthetic – must look good
– economic – … and not cost too much!
Design trade-offs

constraints are contradictory … need trade-offs

within categories:
e.g. safety – cooker controls
front panel – safer for adult
rear panel – safer for child

between categories
e.g. ergonomics vs. physical – MiniDisc remote
ergonomics – controls need to be bigger
physical – no room!
solution – multifunction controls & reduced functionality
Fluidity

• do external physical aspects reflect

logical effect?
– related to affordance (chap 5)

logical state revealed in physical state?

e.g. on/off buttons

inverse actions inverse effects?

e.g. arrow buttons, twist controls
inverse actions

• yes/no buttons
– well sort of

• ‘joystick’

• also left side control

spring back controls

• one-shot buttons
• joystick
• some sliders

good – large selection sets

bad – hidden state
 a minidisk controller

twist for track movement

series of spring-back controls pull and twist for volume
each cycle through some options – spring back
–natural inverse back/forward – natural inverse for twist
physical layout

controls:
logical relationship
~ spatial grouping
compliant interaction

state evident in rotary knobs reveal internal state

and can be controlled by both user
mechanical buttons and machine
Managing value

people use something

ONLY IF
it has perceived value
AND
value exceeds cost

BUT NOTE
• exceptions (e.g. habit)
• value NOT necessarily personal gain or money
Weighing up value

value
• helps me get my work done
• fun
• good for others
cost
• download time
• money £, $, €
• learning effort
Discounted future

• in economics Net Present Value:

– discount by (1+rate)years to wait

• in life people heavily discount

– future value and future cost
– hence resistance to learning
– need low barriers
and high perceived present value
example – HCI book search

• value for people who have the book

helps you to look up things
– chapter and page number

• value for those who don’t …

sort of online mini-encyclopaedia
– full paragraph of context

… but also says “buy me”!!

… but also says “buy me”!!
Value and organisational design

• coercion
• tell people what to do!
• value = keep your job
• enculturation
• explain corporate values
• establish support (e.g share options)
• emergence
• design process so that
individuals value  organisational value
General lesson …

if you want someone to do something …

• make it easy for them!

• understand their values