Transcript Norman Ch2

Norman Chapter 2
Psychology of Everyday
Actions
Jeff Offutt
http://www.cs.gmu.edu/~offutt/
SWE 205
Software Usability and Design
Making Mistakes
• When people make mistakes with UIs, they either:
1. Blame themselves for not paying attention
or
2. Blame themselves for being incapable
• They seldom blame the UI !
• This is deadly in math, because every subject
builds on the previous
– Once we fall behind, we think we’re too dumb for
math
– EVERYbody falls behind sometime
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© Jeff Offutt
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Models Vs. Reality
A
B
Naive guesses are A or B
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C
A little physics says that the ball
keeps its horizontal motion even
after being dropped
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“Stuff” Happens
• If an error is possible, someone will make it
• Good UI designers must assume all possible
mistakes will happen
– Design to minimize the chances of mistakes
– Design to minimize the consequences of mistakes
– Design to maximize recovery from mistakes
Do NOT assume users are perfect
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Helping Users Choose Action
1. Visibility : The user can see the state of the
device and how to use it
2. Good conceptual model : The device works
the way the users expect
3. Good mappings : Users can see relationships
between actions and results, controls and effects,
and state and appearance
4. Feedback : The device tells the user what
happened at every step
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Summary
When something seems easy to use
it was probably hard to design
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© Jeff Offutt
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