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Summary
Darn these hooves!I hit the wrong switch again!Who designs these instrumentPanels, raccoon?!
Don Norman
Professor at Northwestern and Principal of Nielsen Norman group
Previously Professor at UCSD, senior positions at Apple & HP
ACM/CHI Lifetime Achievement Award
Prolific author http://www.jnd.org/
Here are some
Affordances are important Minimize the gulf of interpretation and
gulf of execution Use natural mappings Make state visible Use a conceptual model that makes
sense Provide feedback
Daily Challenges
How many of you can use all the functionality in yourVCRDigital watchCopy machineStereo systemPlumbing fixtures
Hall of Shame Example
Leitz slide projectorTo move forward, short pressTo move backward, long press
What happens when you get frustrated?
Changing Ringer Volume
Press “Program” Press “6” Set volume
Low - Press “1”Medium - Press “2”High - Press “3”
Press “Program”
Affordances
Perceived and actual properties of an object that determine how it could be usedChair is for sittingButton is for pushingDoor handle is for ….Scroll arrow is for …Icon is for …
Door Opening Affordances
1 2 3 4 5
6 7
Which doors are easy to open?
Which doors are hard to open?
Why?
Affordances in interfaces
Interfaces are virtual and do not have ‘real’ affordances like physical objects
Interfaces have ‘perceived’ affordances Learned conventions of arbitrary mappings
between action and effect at the interface Some mappings are better than others
Mantra
Complex things may need explanation, but simple things should notIf a simple thing requires instructions,
it is likely a failed design
Designing for People
Norman’s 2 main principlesProvide a good conceptual modelMake things visible
• Affordances is part of this
Conceptual Models
People build their own systems of how things workExample - thermostat
Designer can help user foster an appropriate conceptual modelAppearance, instructions, behavior...
Conceptual Models
Mental models are not always right Two Classes:
Functional model• Stimulus - response• “Press the accelerator once, then turn the key”• At surface or superficial level
Structural model• Deeper sense of why it happens, not just what
happens• “Press the accelerator to engage the automatic
choke on a carburetor”
Visibility
When functionality is hidden, problems in use occurOccurs when number of functions is
greater than number of controls When capabilities are visible, it does
not require memory of how to useRecognition over Recallin the world vs. in the head
About that VCR…
That old joke - “how many of you have a VCR that is blinking 12:00?” :-)
Still true today :-(
Mapping
Relationship between control and action/result in the world
Take advantage of physical analogies or cultural understandingsGood:
• Car, various driving controls• Mercedes Benz seat adjustment example
Bad• Car stereo - Knob for front/back speakers
Why Not Design Better
Stove
Speakers
Physical, monetary,convenience, etc.,constraints dictateotherwise
Feedback
Sending information back to the user about what has been done
Includes sound, highlighting, animation and combinations of these
e.g. when screen button clicked on provides sound or red highlight feedback:
“ccclichhk”
Example
ScissorsAffordances - Insert somethinginto holes
Constraints - Bigger hole forseveral fingers, small for thumb
Mapping - How to insert fingersinto holes suggested by visibleappearance
Conceptual model - Suggested byhow parts fit together and move
Execution-Evaluation cycle
Norman (DOET, p. 46)
UserGoals
PhysicalSystem
Gulfof
Execution
Gulfof
Evaluation
Goals, Execution, Evaluation
Physical System
GoalsWhat we
want to happen
ExecutionWhat we
do to the world
EvaluationComparing what happened
with what we wanted to happen
(Gulf of Execution) (Gulf of Evaluation)
Execution
GoalsWhat we
want to happen
An intention to actso as to achieve the goal
The actual sequence of actionsthat we plan to do
The physical execution of that action sequence
Physical System
Evaluation
GoalsWhat we
want to happen
Evaluation of the interpretationswith what we expected to happen
Interpreting the perception accordingto our expectations
Perceiving the stateof the world
Physical System
Seven Stages - All Together
GoalsWhat we
want to happen
Evaluation of the interpretationswith what we expected to happen
Interpreting the perception accordingto our expectations
Perceiving the stateof the world
An intention to actso as to achieve the goal
The actual sequence of actionsthat we plan to do
The physical execution of that action sequence
Physical System
Implications – Which Gulf does these Address?
Make current state and action alternatives visible Need good conceptual model with consistent system
image Interface should include mappings that reveal
relationships between stages User should receive continuous feedback Provide affordances
Goal: Minimize Gulfs
Gulf of Execution Conceptual model Affordances Natural mappings
Gulf of Evaluation Make state visible Feedback