Human Capabilities:
Mental Models
CS352
Announcements
• Project – your users: due next Wed. 7/7
• Quiz #3 (human capabilities) next Tue.
2
Hints:
Team Process Improvement
• List risks and what you’ll do if they materialize.
• Agree on a process for working out disagreements in
direction.
– We should use a web interface!
No, we should use portable bar-code readers!
– eg: votes? eg: quality data from CogTool? eg: joint visits to office hours?
• Do a post-mortem after every hand-in or grade received
– What went right in our process?
• Data, not finger-pointing: “we got an A-”.
– What went wrong in our process?
• Data, not finger-pointing: “we had to pull an all-nighter because we started too late”
– What will we do differently from now on?
– Write it down and revisit next time.
Mental Models
http://www.youtube.com/watch?v=T2EIx9rBy78
Mental Models
= How to use the system (and how the system
works).
• Users build these in their heads.
• Developed over time.
– Not always correct (and usually not
complete).
• Thermostat example.
– Why do users build these?
• Rote mem is hard, explained-by memory easier.
• Mental model is an explanation.
– If user’s mental model is correct, will have an
easier time using the system.
How to help user’s mental
model be correct
• Remember Norman’s 2 Gulfs?
1 Useful feedback in response to inputs
(Evaluation).
2 Context-sensitive devices for guidance
(Execution).
3 Ways of interacting with UI consistent with
underlying workings (Eval+Exec).
• Activity: sketch a thermostat UI idea that
does 1, 2, or 3.
How people do things:
the 7 stages of an action
• Norman, at a conf in Italy.
– Speaker needed to show film, had trouble
threading it into projector.
– Many people cam up to help, none
succeeded.
– Finally technical was called, who quickly
threaded it correctly.
• Q: Why so hard? A: Structure of an action
as relate to the Gulfs.
The 7 stages
• 1=goal. 2,3,4=execution. 5,6,7=evaluation.
1
2
3
4
7
6
5
The 7 stages (cont)
• 1 goal: “what” we want to do.
– Example.
• 2. execution intention (from what to how
but top-level without details)
– Example.
• 3. execution: sequence of actions.
– Example.
• 4. execution: physicall do them (to objects
in the world)
– Example.
The 7 stages (cont.)
• 5. evaluation: perceiving (senses) what the
world did in response (with our eyes, etc.)
– Example.
• 6. evaluation: interpreting (brain) the
perception.
– Example.
• 7. evaluation: comparison of interpretation
with goal.
– Example.
The 7 stages (cont.)
• Gulf of Execution.
– How to get from 1 to 2, 2 to 3, or 3 to 4.
– Example.
1
2
3
4
The 7 stages (cont.)
• Gulf of Evaluation.
– How to get to 5 at all, 5 to 6, 6 to 7.
– Example.
1
7
6
5
The 7 stages as design aids
• To find problems, apply these to any task
in a UI:How easily can determine ...
– 1. Goal: ...the purpose of the device/feature?
– 2. Exec: ... what actions are possible?
– 3. Exec: ...the mapping from intention to
specific physical movements?
– 4. Exec: ...how to actually perform the action?
– 5. Eval: ...what state the system is in?
– 6. Eval: ...what “that (feedback in UI)” means?
– 7. Eval: if system is in desired state?
Activity
• In pairs (cell phone owner, other)
– Cell phone owner “drives” (no thinking, just hit
keys when told to).
– Other “thinks” (no access, just tell driver what
to do).
• Task:
– Make ALL display dimming go away. It should
never dim at all under any circumstances.
• Ask the 7 questions at each stage.
• Write down problems you experience and
the step you are at in the 7 stages.
To find solutions
• Consider these remedies.
– Visibility: to reveal
• state (5),
• show what actions available (2).
– Good mappings revealing:
• relationships between actions and results (2),
• controls and effects (3),
• system state and what is visible (6, 7)
– Feedback
• every action provides immediate feedback of
results (5,6,7)