Human Capabilities:
Mental Models
CS352
Announcements
• Notice upcoming due dates (web page).
• Where we are in PRICPE:
– Predispositions: Did this in Project Proposal.
– RI: Research is in process (studying users), due
Friday. Should lead to Insights.
– CP: Concept and initial (very low-fi) Prototypes
due soon (see schedule).
– Evaluate throughout, repeat iteratively!!
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
= How to use the system (and how the system
works).
• Users build these in their heads.
• Developed over time.
– 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.
– Not always correct (and usually not
complete).
How to help user’s mental
model be correct
• Remember Norman’s 2 Gulfs?
– Gulf of Evaluation, Gulf of Execution
– We can use them to understand how to help:
1 Useful feedback in response to inputs (Evaluation).
2 Ways of interacting with UI consistent with
underlying workings (Eval+Exec).
3 Context-sensitive devices for guidance (Execution).
Activity: Thermostat
• 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, ad trouble
threading it into projector.
– Many people came 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.
• (drawing)
The 7 stages (cont)
1. goal: “what” we want to do.
– Example.
The 7 stages (cont)
2. execution: intention (from what to how but
top-level without details)
– Example.
3. execution: sequence of actions.
– Example.
4. execution: physically do them.
– 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.
• Gulf of Evaluation.
– How to get to 5 at all, 5 to 6, 6 to 7.
– Example.
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.
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)