Learnability 3

Question 1

Metaphors 1

Answer 1

• Bring the real world into your interface making it highly learnable
• Advantages:
• Hooks into users existing mental models very easily
• Conveys a lot of knowledge about interface model
• Users can guess how things work
• Basic rule: use it if you have one, don’t if you dont

Question 2

Metaphors 2

Answer 2

• Dangers:
• Often hard for designers to find one
• May be deceptive
• May be constraining
• Metaphors always breaks down
• Using a metaphor doesn’t save an interface that does a bad job communicating itself to the user

Question 3

Natural Mapping: Consistency of Layout

Answer 3

• Natural mapping of functions to controls
• When possible, the physical arrangement of controls should match arrangement of function
• Direct mapping is the best mapping
• Car turn signals mapping isn direct but it’s natural why? Probably because of the placement on steering wheel

Question 4

Affordances 1

Answer 4

• Perceived and actual properties of something, primarily, properties that determine how something can be used
• How UI communicates non verbally, telling you how to operate it
• Affordances are learned from experience e.g. recognise listboxes to make a selection

Question 5

Affordances 2

Answer 5

• Perceived vs Actual:
• Perceived affordance disagrees with what it can actually do
• Perceived affordance is important for UID
• Actual ability without any perceived ability is undesirable

Question 6

Use Appropriate Affordances

Answer 6

• Buttons
• Drop down arrows
• Texture
• Mouse cursor
• Highlight on mouseover

Question 7

Evolution of Hyperlinks and Buttons

Answer 7

• Affordance tend to diminish rather than increase

- The drive toward simplicity is a constant force in UI design

Question 8

Actions should have immediate visible effects

Answer 8

• Hand in hand with affordance is feedback
• How the system changes visibly when user performs an action
• Low level feedback (object takes notice of input) e.g. a button push
• High level feedback (result of the action) e.g. new web page starts to load

Question 9

Perceptual Fusion 1

Answer 9

• An interesting aspect of human visual system
• Our perceptual processor runs at a certain frame rate:
• Grabbling one frame very cycle
• Each cycle takes Tp seconds
• Two events occurring less than the cycle time apart are likely to appear in the same frame
• Cycle Time: Tp is around 100ms [50-200ms]
• Depends on the individual and stimulus

Question 10

Perceptual Fusion 2

Answer 10

• The way we perceive a sequent of frames as a moving pic
• Consequences:
• Lower bound on the frame rate for believable animation (1/Tp frames/sec is enough to perceive a moving pic (10 fps is OK, 20 fps is smooth)
• Upper bound on good computer response time (computer response < Tp feels instantaneous)

Question 11

Response Time

Answer 11

• 1-5s: progress bar displayed

Question 12

Feedback: Visible Navigation State

Answer 12

• Where am i now
• Breadcrumbs
• Pagination
• Tabs

Question 13

Feedback: Visible Model State

Answer 13

• System model should be visualised in an UI
• Hard design issues in model visibility:
• WHat to make visible (which aspects of the model)
• How to display it (in what representation)
• The ‘What’ question:
• A tension between visibility (showing more) and simplicity (showing less)
• Should be guided by user’s tasks

Question 14

Feedback: Visible View State

Answer 14

• The current state of the user’s interaction with the UI
• Selection highlight (feedback: whether and what)
• Selection handles (feedback and affordances)
• Feedback is important, don’t over do it