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 officeobjects

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’

W W W

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

• 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

• 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)

• 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