Transcript Document

Last time…
• Conceptual models
– To what is it similar? What metaphors do they
bring to bear?
– What actions can one perform on or with a web
page?
Last time…
• Conceptual models
– What will the users be doing when carrying
out their tasks?
– How will they think about the task?
– What concepts and metaphors will they bring
with them to the system?
– What interaction modes will be most useful?
Conceptual models based on
activities
• Giving instructions
– issuing commands using keyboard and function keys
and selecting options via menus
• Conversing
– interacting with the system as if having a
conversation (e.g., AskJeeves)
• Manipulating
– acting on objects and interacting with virtual objects
(e.g., pong, MS Word)
• Browsing
– Looking through lists, poking around, etc.
Conceptual models based on
objects
• Usually based on an analogy with
something in the physical world
• Examples include books, tools, vehicles
• Classic: Star Interface
based on office
objects
Johnson et al (1989)
Interface metaphors
• Interface designed to be similar to a physical entity but
also has own properties
• Can be based on activity, object or a combination of both
• Exploit user’s familiar knowledge, helping them to
understand ‘the unfamiliar’
WWW
Another Internet metaphor
• WWW as planet earth
• The “superhighway”
• An atlas
– Web sites are:
• Towns
• Points of interest
– Links are roads
• There are “vacation spots” and places we go to work
• Every site has an address
• Sites like Yahoo! provide a yellow pages for locating
goods and services
• Search engines are somewhere between a yellow pages
and visitor center or information desk
Benefits of interface metaphors
• Makes learning new systems easier
• Can expand the audience
• Helps users understand the underlying
conceptual model
Problems with interface metaphors
• Break conventional and cultural rules
– e.g. recycle bin placed on desktop
• Can constrain designers in the way they conceptualize a
problem space
• Forces users to only understand the system in terms of
the metaphor
• Designers can inadvertently use bad existing designs
and transfer the bad parts over
• Limits designers’ imagination in coming up with new
conceptual models
• However, for the most part, metaphor is an
extremely useful tool in constructing user
interfaces.
Metaphor is fundamental to how we
think
- George Lakoff & Mark Johnson
Argument is War
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Your claims are indefensible
He attacked every weak point in my argument
Her criticisms were right on target
I demolished his argument.
I’ve never won an argument with her.
You disagree? Okay, shoot!
If you use that strategy, she’ll wipe you out.
He shot down all of my arguments.
More is up/good is up
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I’m feeling up. That boosted my spirits.
Get up. Wake up. She rises early.
He’s at the peak of health.
I am on top of the situation. He is under
my power.
• My income rose last year.
Future is forward, past is back
• In the weeks ahead of us…
• That’s all behind us…
The conduit metaphor
• The conduit metaphor
– Ideas are objects
– Linguistic expressions are containers
– Communication is sending
The conduit metaphor (cont’d)
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It’s difficult to put my ideas into words.
It’s hard to get that idea across to him
You’re reasons came through to us.
His words carry little meaning.
Your words seem hollow.
The idea is buried in terribly dense
paragraphs.
If you’re interested
• Metaphors We Live By, George Lakoff and
Mark Johnson
• Women, Fire, and Dangerous Things,
George Lakoff
• A conceptual model is what we target as
designers
• Metaphor is useful in building conceptual
models
• A “mental model” is how an individual in
our audience actually perceives what we
have built.
Mental models
• Users develop an understanding of a system
through learning & using it
• This type of understanding is often described as
a mental model
– How to use the system (what to do next)
– What to do with unfamiliar systems or unexpected
situations (how the system works)
• People make inferences using mental models of
how to carry out tasks
Mental models
• Craik (1943) described mental models as
internal constructions of some aspect of the
external world enabling predictions to be
made
• Involves unconscious and conscious
processes, where images and metaphors
are activated
• Deep versus shallow models (e.g. how to
drive a car and how it works)
Everyday reasoning & mental
models
(a)You arrive home on a cold winter’s night to
a cold house. How do you use the
thermostat to get the house to warm up as
quickly as possible?
Everyday reasoning & mental
models
(b) You arrive home very hungry. You look in
the fridge and find all that is left is an
uncooked pizza. Do you set the oven to
bake at 375 degrees (as specified by the
instructions) or turn the oven up higher to
try to warm it up quicker?
Heating up a room or oven that is
thermostat-controlled
• Many people have erroneous mental models
(Kempton, 1996)
• Why?
– General valve theory, where ‘more is more’ principle
is generalized to different settings (e.g. gas pedal,
tap, radio volume)
– Thermostats based on model of on-off switch model
Heating up a room or oven that is
thermostat-controlled
• Same is often true for understanding how
interactive devices and computers work:
– Poor, often incomplete, easily confusable, based on
inappropriate analogies and superstition (Norman,
1983)
– e.g. frozen cursor/screen - most people will bash all
manner of keys
How does Google work?
• Write down the steps you believe Google
follows in finding and ranking search
results for a query you submit.
Now answer the following
questions
• What will be the characteristics of the top
result for the query?
– dog food
• Does your mental model predict a
difference in top results for the queries:
– dog food organic
– food dog organic
– organic dog food
– “organic dog food”
Exercise: ATMs
• Write down the steps you believe an ATM
(cash machine) goes through in order to
enable you to get money.
Exercise: ATMs
• Answer the following:
– How much money are you allowed to take out?
– If you took this out and then went to another machine
and tried the same what would happen?
– What denominations are allowed?
– What information is on the strip on your card? How is
this used?
– What happens if you enter the wrong PIN?
– Why are there pauses between the steps of a
transaction? What happens if you try to type during
them? Can you type ahead?
– Do you count the money? Why?
How did you fare?
• Your mental model
– How accurate?
– How similar?
– How shallow?
• Payne (1991) did a similar study and found
that people frequently resort to analogies to
explain how they work
• People’s accounts greatly varied and were
often ad hoc