Introduction to Graphical Human Machine Interfaces
The Psychology of Everyday Actions
MONDAY, JANUARY 27, 1997
Instructor: G. Bowden Wise
Rensselaer Polytechnic Institute
- We often make mistakes when using devices, software, etc.
- For a complex task, this is reasonable and expected.
- For a simple task (or one that appears so)
- Complex devices (software) will always require some instruction.
- Someone using them without reading the manual (very common among
computer users!) should be expected to make errors and to be
- As designers, we should
design for error:
- minimize the possibility for error
- make errors as ``cost-free'' as possible
- If an error is possible, someone will make it.
- Designers should
- assume all possible errors will occur.
- minimize the chance of errors.
- minimize the effects of errors when they do occur.
- make it easy for users to detect errors.
- make it possible to reverse the effects of an error.
- Misconceptions can be due to ``naive'' or ``folk''
understandings (e.g., Aristotle's naive physics).
- But mostly due to faulty conceptual models we form.
- Models are based on whatever knowledge we have (real or
imaginary, naive or sophisticated).
- Models are constructed out of fragmentary evidence, with a poor
understanding of what is happening.
- People do not have erroneous theories...
- Instead we form mental models to explain what we observe
- With the lack of complete information, we let our imaginations
run free as long as the model accounts for the faults as we
- When something goes wrong, who do we blame?
- For difficulties with technology ...
Simple tasks (or tasks we think others can do) ...
- In more complex cases, we have a tendency to search for the
cause of an event
We find a perceived casual relationship between the thing
being blamed and the result.
- we blame others
- we blame the environment
- We blame problems of other people on their personalities.
- But ... really ...
a faulty mental model is at work!
- Just the opposite happens!
- When we think we did something very well
- we give ourselves credit
- we praise our forceful personalities
- we praise our intelligence
- Others, however, credit our success
- Learned Helplessness
Occurs when a person experiences failure numerous times and then
decide that the task cannot be done ( at least by them! ) so, they are
- Taught Helplessness
Occurs when a person generalizes his instances of failure to other
similar tasks (i.e., I am no good at math or I can't cope with new
- Cycle: you fail at something; you think it is your fault; you
think you cannot do that task; the next time you are confronted with
that same task, you dont even try!
- Not always easy to attribute the blame for a failure
- Dramatic, life-threatening accidents can result when blame is
- When something goes wrong, we strive to find an explanation
- Once we find a suitable explanation, we think the
discrepancy is solved!
- Can mean disaster!
- Three-mile island
- Lockheed L-1011
- Forming the goal.
- Forming the intention.
- Specifying an action.
- Executing the action.
- Perceiving the states of the world.
- Interpreting the state of the world.
- Evaluating the outcome.
- Stages are not discrete entities.
- Not all stages are required for every goal.
- Most goals not satisfied by a single action.
- Numerous sequences
- May span seconds or minutes or hours or days.
- Continuous feedback
- results may spawn other goals and other actions
- goals lead to subgoals
- intentions lead to sub-intentions
- In a large activity, intermediate goals can be forgotten,
discarded, or reformulated.
- Humans do not plan everything.
- We are spontaneous.
- Goals are often ill-formed and vague.
- We respond to events in the world.
- We are data-driven, as events in the world around us
unfold, we introduce new goals, which lead to new actions, as
opportunity allows us.
Refers to how well the system/device enables a person to perform the
intended actions directly without extra effort.
- How well does the system allow the person to do the intended actions
- Do the actions provided by the system match those intended by
Reflects the amount of effort a person must exert to interpret the
physical state of the system and to determine how well the
expectations and intentions have been met.
- Does the system provide a physical representation that can be
- Can the person easily interpret representation in terms of his
intentions and expectations?
- Questions we can ask to ensure the gulfs are ``bridged'':
How easily can the user ...
- Provide a good conceptual model
Coherent system image.
Consistency in presentation of operations and results.
- Make things visible
Is the state of the system easily visible?
Can alternative actions be easily found?
- Use a good mapping, a natural one if possible
Show relationships between
- actions and results
- controls and their effects
- system state and what is visible
- Provide feedback
Continuous feedback of results and actions.
Wed Feb 12 12:36:09 EST 1997