. Earl E. Hansen, CIE
Difficult to Discuss/Analyze
Relatively new field
Still trying to:
define its boundaries
define its terminology
define its taxonomy
Seems trivial on the surface
No matter how good a system or
design is, people will make mistakes
some subscribe to the concept of “Normal Errors”
errors that are inevitable in
Systems Can Encourage Errors
Errors are often attributed to the action of an individual
there are often a set of
forces & preceding events that lead up to the error.
These forces & events are difficult to anticipate.
Reaction is to punish individual and not to examine the system
Studying Human Error
Reinforces existing guidelines for good design.
Is the analysis o
f human performance.
Expects humans to make errors
Focus on error tolerance
Focus on error recovery
Focus on error prevention
New technologies will succeed or fail based on our ability to minimize the
the characteristics of peopl
the characteristics of the things we create
Cognitive Science (Engineering)
A mix of different disciplines (psychology, philosophy, neuroscience, & artificial
Reviews specifics of human performance & how it
can be improved.
Physical and Physiological.
What Is Human Error?
“Human error: an inappropriate action, or intention to act, given a goal and the
context in which one is trying to reach that goal.” Ramon
A Theory of Cognition
Accidents typically occur due to mental error.
There are three basic kinds of mechanisms of thought
The ability to carry out a task; skill
ocessing and performance refers
actions that are automatic and easy to due
to an acquired skill. Example: getting out bed.
Putting on a T
shirt, or opening a door
which are unconscious actions one doe not
need to explicitly “think about” to
omplish. Automatic which arm in what
Matching the context & problem currently
facing the actor. These rules are typically of
the “if X then Y” form, can be based on past
experience, explicit instructions, etc.
in leaving a room,
pushes the door to exit (automatic skill). If the
door does not open one start down a list of
reasons. Locked, pull, etc.
based processing does not solve the problem,
we fall back on knowledge
processing (tend to
based solutions since they require less
cognitive effort on
our part). Occurs when faced
with novel or unfamiliar situations, or where low
are not appropriate (e.g. making strategic
decisions, diagnosis, etc.) Involves processing
symbolic information (suits in card deck) reduces
cognitive effort. Cognitive
mechanisms are Slips &
Slips: Errors of Action
Action not in accord with ones intentions: a good plan but poor execution. i.e.
fumble on a good play. They are p
art automatic, unconscious actions, slips are
unintended acts due to a break in the routine.
Slip Error Mechanisms
doing something automatically one did not intend to do. Fell into a
pattern one performs frequently.
to tell self correctly what one wants to do. Occurs when
intended action is similar to other actions done often.
Associative activation slips
occur when the brain makes a faulty connection or
mental association between tow ideas, often when one is an exter
nal stimulus that
typically provokes a certain action. e.g. answering phone when hearing the
Loss of Activation slips
occur when one loses track of what they are doing or
trying to do (the activation of the process). Essentially a temporary memor
often due to interruption, asked a question, handed something. e.g. “now why did
I get up to come into this room in the first place?”
Errors of Intention
Stem from cognitive breakdowns; often influenced by external system
s. A planning failure, when actions go as planned
but the plan was bad.
These are errors of judgement, influence, etc., that result in an incorrect intention,
incorrect choice of criterion, or incorrect value judgement. Mistakes are the real
n the analysis of human error. Slips can be prevented through checks
built into tools/equipment.
the wrong rule chosen due to misperception of the situation
misapplication of rule
The most complex of
Occurs from a lack of or misapplication of knowledge