More on Design of Everyday Things

Turn it up, or shut it down?

Welcome to the hall of shame!

●signifiers are present●this is an execution problem

○ specifically the “perform” step●should there really be a one-touch shortcut

to close all tabs?

Bad Microwave

My microwave has a problem.It has a huge problem, actually.

Can you identify it?

Bad Microwave

● The problem with this microwave is that there is no way to specify “Add thirty seconds” after I input a number.

● Therefore, my food can only be cooked in thirty second increments, if I’m lazy.

● The microwaves programming only allows me as a user to input a specific time, or any product of thirty seconds.

So how does a designer help users acquire the right model?

• Visibility

• Affordances

• Constraints

• Mappings

• Feedback

Constraints• Limit the range of possible actions• Physical Constraints

– Only some possibilities are physically possible (only one way to put a VCR tape in a player)

• Semantic Constraints– Only some possibilities make sense

• Cultural Constraints– Only some possibilities are acceptable

• Logical Constraints– General principles: e.g., every part should be used

Feedback

• Remember that people will build models– And feedback leads to causal models: “if Y happened

after X, then X caused Y”

• So provide the proper feedback immediately: respond to user actions – don’t hide the results!– Did I press the button? (visual and/or audio feedback)

• All actions should have effects– Promote exploration

Knowledge In The World

Recognition, not Recall

Partial, “good enough” descriptions stored

Put knowledge in the world

• So users don’t have to keep it all in their heads– Menus, toolbars– Agendas– Graphical workspaces

• Provide memory aids– so users don’t have to remember information

between screens

To err is human…

• Slips – errors in automatic actions: easy to detect– Capture errors

– Description errors

– Data-driven errors

– Associative action errors

– Loss of activation errors

– Mode errors

• Mistakes – errors in intention or logic: hard to detect

Preventing errors

• Avoiding slips– Different things should look different– Consistent confirmation is not useful– Immediate confirmation may not be useful

• Simplify tasks– Make task structure narrow or shallow

Ooops, I opened my trunk

Controls to open trunk and access gas tank are right next

to each other

More ways to prevent errors

• Support recovery– Undo and backups

– Support exploration toward a goal

• Prevent errors with forcing functions –failure in one step means later steps can’t be done– Make illegal actions unavailable

– Disable buttons or menus

– Turn illegal actions into legal ones

Last resort - standardization

• Fewer things to memorize

• Quicker to learn

• Clocks should run clockwise

• But note that standards are culture-dependent!

“Standards” and cultures• What does the color red mean?

– US – danger, warning, …– India – purity

• What color should a wedding dress be?– US – white– India – red & yellow

• How do you turn on a faucet?– US – counter-clockwise– UK – clockwise

• Problems with icons – mailboxes, trashcans, …

Applying the principles

A usable design - scissors• Affordances

– Holes for something to be inserted

• Constraints– Big hole for several fingers, small hole for thumb

• Mappings– Between holes and fingers suggested and constrained by

appearance

• A cultural standard• Conceptual model

– Implications of actions clear – feedback is immediate

A problematic design – digital watch

• Affordances– 4 buttons to push, but not clear what they do

• Constraints, mappings– Unknown – no natural relations or constraints

• Transfer– Little/none from analog watches

• Standardization– Still quite variable

How do I pump the gas?

“Push To Start”

Design Principle Problems

• Visibility

• Affordances

When does the bottom light go on?

Design Principle Problems

• Conceptual Model

• Feedback

Setting Options in MS Word

Design Principle Problems

• Conceptual model – “What happened?!?”

Which string turns on the fan, which turns on the light?

Design Principle Problems

• Mappings

What’s that thing in the corner?

It’s a mop sink!

Design Principle Problems

• Affordances

• Conceptual Model

• Standardization

How do you raise/lower this screen?

Design Principle Problems

• Conceptual Model

• Mappings

Wrapping up DOET

• Reflecting on DOET:– Was written 25+ years ago– Talks about things like doors, slide projectors,

refrigerators, not GUIs– So how well does it apply to designing GUIs in

2015?

Next Steps

• For next time– Begin discussion on how to interact with users

• Project – Friday, September 11– Project Proposal Due– But we won’t do studio on this until next

week.