metaphors and styles of human-computer interaction
Post on 20-Dec-2015
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The psychology of metaphors
Like affordances, having a metaphor can tell you how you might use something.
Unlike affordances (which are direct), metaphors are indirect (require more inferences)
The psychology of metaphors
a metaphor provides a lot of information it enables the transfer of skills good metaphors provide natural mappings metaphors are not taken literally they can highlight underlying assumptions metaphors are not symmetrical they can be violated
The psychology of metaphors
metaphors can be mixed (e.g., windows and desktops)
metaphors can be misleading (putting a disk in the trash)
some things don’t seem to have any obvious metaphor (ex: UNDO)
one metaphor is better than another if it leads to more correct predictions about a system’s behavior.
Popular metaphors for computers computer as vast library (Memex, 1945) computer as giant calculator (ENIAC, 40s-50s) computer as intelligent assistant (Licklider, 1957) computer as sketchpad (Sutherland, 1962) computer as tool or typewriter (Engelbart, 1963) computer as human pretender (Weizenbaum, ‘60s) computer as network (Taylor, 1968) computer as book (portable) (Kay, Xerox PARC) computer as desktop/windows (Xerox PARC, ‘70s)
with objects computers for the rest of us (Apple, 1984)
More or less successful metaphors text editing as using a typewriter voice mail as answering machine or mailbox data as files (in folders or directories),
represented as icons on desktop/in windows deleting a file as throwing it in the trash applications as tools (sometimes w/ icons) programming as building objects programming as directing actors on a stage applications as agents
Metaphors often suggest styles of interaction
Some styles of interaction: Commands (& queries, keyboard shortcuts) Menus (and W.I.M.P. interfaces) Direct manipulation Conversation (often w/ speech or natural language) Browsing Forms and spreadsheets Immersive environments
Metaphors often suggest styles of interaction
Some styles of interaction: Commands (& queries, keyboard shortcuts)
Typing in choices to a vending machine Telling a dog to go fetch Interacting with VMS, DOS, Unix, or protocols such as
Telnet, ftp, etc. Programming your VCR to record a TV show
Command interface advantages Domain-specific language
Similar to scripting language The user tells the system what to do
e.g. tell the time, copy a file, save a file The user is in control (takes the initiative) Very common conceptual model for operating a
device (little or no intelligence in the device) Main benefits:
Powerful (especially for experts and frequent users) Supports fast and efficient interaction Good for repetitive kinds of actions
Example: Copy command (DOS) Copies files from one location to another. The destination
defaults to the current directory.
> copy file1 [destination] If multiple files are to be copied, the destination must be a
directory, or an error will result.
> copy file1 file2 file3 [destination] Files may be copied to devices. To send file to printer:
> copy file lpt1
To display file on screen ("console"): (alternatively: type file)
> copy file con
>
No feedback given after one of these commands; just a prompt >
Equivalent Unix command: cp
Command interface drawbacks
The user needs to know exactly where the information is and how it’s organized
The user needs to know command syntax No tolerance whatsoever for errors Can be cryptic, especially if little feedback is given
Another example: SQL queries
Which companies sell everything FabCo sells?
(List companies such that there does not exist an item sold by FabCo that they do not sell.)
“Which companies sell everything FabCo sells?”
select distinct X.name from suppliers X where 0 = (select count (*)from suppliers Ywhere Y.name = “FabCo”and 0 = (select count (*)
from suppliers Zwhere Z.name=X.nameand Z.item=Y.item))
(Schneiderman, 1986)
“Since computers can display information 1000 times faster than people can enter commands, it seems advantageous to use the computer to display large amounts of information and allow novice and intermittent users simply to choose among the items.”
Styles of interaction
Commands (& queries, keyboard shortcuts) Menus (and W.I.M.P. interfaces) Direct manipulation Conversation (often w/ speech or natural language) Browsing Forms and spreadsheets Immersive environments
Menus
Users are given predetermined choices Are often part of a
WIMP interface (point & click) Windows and window managers IconsMenusPointing devices
Menus
enforce a hierarchy on the user’s goals represent well-trodden paths - you can do
only what the designer envisioned You cannot filter and combine the world in
novel ways
Decisions in menu design
What is the task hierarchy? How to order or group items? How to trade off depth vs. breadth? What labels to choose? Whether to include shortcuts?
Menu types (not mutually exclusive)
Permanent Pull-down Fall-down Pop-up
Binary Extended Multiple selection Radio buttons Embedded
Styles of interaction
Commands (& queries, keyboard shortcuts) Menus (and W.I.M.P. interfaces) Direct manipulation Conversation (often w/ speech or natural language) Browsing Forms and spreadsheets Immersive environments
Direct Manipulation Interfaces
Representations behave as if they were the objects they represent.
This reduces the distance between users and their goals.
What You See Is What You Get
(WYSIWYG)
(Hutchins, Hollan, & Norman, 1986)
Direct manipulation Invented by Ivan Sutherland (Sketchpad, 60’s) Term was coined by Ben Shneiderman (1983) Theory developed by Hutchins, Hollan, & Norman Involves dragging, selecting, opening, closing
and zooming actions on virtual objects Exploit’s users’ knowledge of how objects behave
in the physical world (various metaphors) Consistent with “what you see is what you get”
(WYSIWYG)
Features of direct manipulation
continuous representation of the objects of interest
physical actions, not complex syntax
Example: copying a file to a diskette:
> copy file.txt to b:\file.txt
versus
dragging a file icon to a diskette icon
(move vs. copy confusion)
Features of direct manipulation
continuous representation of the objects of interest
physical actions, not complex syntax rapid, incremental, reversible operations with
immediate visual feedback
Features of direct manipulation
continuous representation of the objects of interest
physical actions, not complex syntax rapid, incremental, reversible operations with
immediate visual feedback easy to learn, easy to remember can operate upon output representation and
use it as input back to the system
Direct Manipulation
(semantic distance)
Gulf of Execution
Gulf of Evaluation
(articulatory distance)
SystemUser’s Goals
What do Ido now?
What does that mean?
Hutchins, Hollan, & Norman
Why are DM interfaces enjoyable?
Novices can learn the basic functionality quickly Experienced users can work extremely rapidly to carry
out a wide range of tasks, even defining new functions Intermittent users can retain operational concepts over
time Error messages are rarely encountered Users can immediately see if their actions are furthering
their goals and if not, do something else Users experience less anxiety Users gain confidence and mastery and feel in control
Some problems with D.M. Sometimes: information overload or screen clutter Not all tasks can be represented by objects
it’s hard to represent abstract things DM must function in the “here” and “now” icons can be just as cryptic as words (the Vocabulary Problem:
stay tuned)
With DM, user is responsible for doing everything; but some tasks are better achieved by delegating! e.g. spell checking repetitive actions are tedious! Moving a mouse around the screen can be slower than pressing
function keys to do same actions
Some DM metaphors are taken too literally
Debate about styles of interaction
Direct Manipulation (tool metaphors)
v.
Conversation (agent metaphors)
(Schneiderman, 1986)“People are different from computers, and human-
human interaction is not necessarily an appropriate model for human operation of computers. Since computers can display information 1000 times faster than people can enter commands, it seems advantageous to use the computer to display large amounts of information and allow novice and intermittent users simply to choose among the items.”
(Schneiderman, 1986)“People are different from computers, and human-
human interaction is not necessarily an appropriate model for human operation of computers. Since computers can display information 1000 times faster than people can enter commands, it seems advantageous to use the computer to display large amounts of information and allow novice and intermittent users simply to choose among the items.”
But what about:
“Which companies sell everything FabCo sells?”
Styles of interaction
Commands (& queries, keyboard shortcuts) Menus (and W.I.M.P. interfaces) Direct manipulation Conversation (often w/ speech or natural language) Browsing Forms and spreadsheets Immersive environments
Dialogue systems May take initiative Underlying metaphor is having a conversation
with another person Ranges from simple voice recognition systems
to more complex ‘natural language’ dialogues Examples include dialogs about timetables,
search engines, advice-giving systems, help systems
May (or may not) consist of anthropomorphic agents who converse with you or are part of an interface, e.g. Microsoft’s Bob and Clippy
Agents
A metaphor for an “intelligent” process that takes some initiative and perform tasks on the user’s behalf
The user delegates responsibility to the agent.
This feels very different from direct manipulation!
Agents can be amplifiers or alternatively, prosthetics (2 distinct metaphors for agents)
Tasks for Agents (Laurel; Maes) Delegation Information retrieval - Web “bots” Sorting, organizing, filtering Coaching, tutoring, providing help Reminding Programming, doing repetitive things Advising Entertaining Navigation
Agents (anthropomorphic or not)
The most obvious metaphor for an interactive system that seems intelligent or takes initiative may be a human-like character.
(But note: agents can be non-anthropomorphic as well… a form can take initiative and act “intelligent” by filling in the right values automatically.)
Food for thought:
To what extent is dialog with a person similar to interacting with a computer?
(Shneiderman: not at all!)
(Others: If the system can take the initiative and act “intelligently”, then conversation is a good metaphor for interacting with an agent.)
Should representations ever be anthopomorphic?
CON: Ben Shneiderman
Sherry Turkel
Joseph Weizenbaum (Eliza)
PRO: Brenda Laurel
I say: It depends on the situation!!
Drawbacks of delegation
“Intelligent” interfaces can be unpredictable.
How do you come to “trust” your agent? Are anthropomorphic interfaces honest? There may be problems with
anthropomorphizing an interface (Shneiderman’s arguments)
Theater and stage metaphors
(Brenda Laurel; Laura Gould)
Interfaces are like theater - we suspend disbelief.
Claim: Anthropomorphizing an interface is not a problem: People aren’t so easily fooled.
(This contrasts w/ Shneiderman’s claims.)
Initiative
Some kinds of human conversations are scripted - who takes the initiative is relatively fixed.
In other kinds of conversation, neither person takes all the
initiative. Ideally, initiative should be flexible.
Human-Computer Dialog
What can go wrong? A dialog can be under-determined.
when the user is mystified about
what to do next and is
forced to take the initiative.
(a blank screen, cryptic commands)
(Harold Thimbleby)
Human-Computer Dialog (cont.)
A dialog can be over-determined
when a system is authoritarian
and takes too much initiative.
(unnatural constraints)
Advantages: reduces the consequences of errors what the user does is predictable
Dialog Design
Avoid under-determined dialogs by providing help and by reducing options.
Avoid over-determined dialogs by letting users undertake tasks in flexible orders.
Don’t force them to do unnecessary things. Support alternative styles of interaction
whenever possible
Different users are different!
Interfaces that take the initiative are better for novices.
Interfaces that let the user take the initiative are better for experts.
An interface is over- or under-determined with respect to a particular user.
Direct manipulation and menu interfaces are sometimes (not always)
over-determined. Command languages and natural
language are sometimes (not always)under-determined.
Pros & cons of conversational style of interaction Dialogue allows users, especially novices and
technophobes, to interact with the system in a way that is familiar. makes them feel comfortable, at ease, not scared
Misunderstandings arise when the system fails to parse what the user says.
Sometimes interfaces pretend to use natural language, which can lead to problems. e.g. child types into a search engine, that uses
natural language the question: “How many legs does a centipede have?” and the system responds:
You asked: How many legs does a centipede have? J eeves knows t hese answer s:
Wher e can I f ind a def init ion f or t he mat h t er m
leg?
Wher e can I f ind a concise encyclopedia ar t icle on ? cent ipedes?
Wher e can I see an image of t he human
appendix?
Why does my leg or ot her limb f all asleep?
Wher e can I f ind advice on cont r olling t he gar den pest ?
millipedes and cent ipedes?
Wher e can I f ind r esour ces f r om Br it annica.com on leg ?
Styles of interaction
Commands (& queries, keyboard shortcuts) Menus (and W.I.M.P. interfaces) Direct manipulation Conversation (often w/ speech or natural language) Browsing Forms and spreadsheets Immersive environments
Exploring and browsing
Similar to how people browse information with existing media (e.g. newspapers, magazines, libraries, pamphlets)
Information is structured to allow flexibility in way user is able to search for information e.g. multimedia, web
Browsers, hypertext, links
Forms and spreadsheets
Forms can vary from over-determined (enforcing a fixed order) to quite flexible (allowing user initiative)
Spreadsheets are extremely flexible, allowing “user programming”. They can sometimes be underdetermined
Immersive environments
Virtual reality (stay tuned) Often mimic real life (representations
are highly literal; go well beyond metaphors)
Different styles of interacting lend themselves to very different metaphors Commands
typing commands via keyboard; function key shortcuts Menus
selecting from pre-determined choices Direct manipulation
acting on objects and interacting with virtual objects Conversational dialogue systems
interacting with the system as if having a conversation Exploring, browsing, & foraging for information
finding out and learning things browsers (different from menus)
Choose the right interaction style and the right metaphor
Understand how the system works.(use the system yourself)
(ask engineers)
Figure out what problems users have.(watch them use similar systems)
(create prototypes and watch users)
Generate metaphors and examine their properties.
Ask these Qs: Does the metaphor have enough structure? Is the structure relevant to the application or
problem? (or is it superficial?) Is the metaphor easy to represent? Concrete
enough? Will the users “get it”? Can it be extended? Is the metaphor misleading? Annoying? Does the metaphor fit with the style of interaction?
Problems with interface metaphors
Sometimes they break conventional and cultural rules e.g. recycle bin placed on desktop
Can overly constrain designers in the way they conceptualize a problem space
May conflict with principles of good design Forces users to understand the system in terms of the
metaphor Designers can inadvertently use bad existing designs
and transfer the bad parts into the new designs Limits designers’ imagination in coming up with new
conceptual models