Human error has long been of
interest, but only in recent decades has there been serious effort to understand
human error in terms of categories, causation, and remedy. There are several
ways to classify human errors. One is according to whether it is an error of omission
(something not done which was supposed to have been done) or commission (something
done which was not supposed to have been done). Another is slip (a
correct intention for some reason not fulfilled) vs. a mistake (an
incorrect intention which was fulfilled). Errors may also be classified
according to whether they are in sensing, perceiving, remembering, deciding, or
acting. There are some special categories of error worth noting which are
associated with following procedures in operation of systems. One, for example,
is called a capture error, wherein the operator, being very accustomed
to a series of steps, say, A, B, C, and D, intends at another time to perform
E, B, C, F. But he is “captured” by the familiar sequence B, C and does E, B,
C, D.
As to effective therapies for
human error, proper design to make operation easy and natural and unambiguous
is surely the most important. If possible, the system design should allow for
error correction before the consequences become serious. Active warnings and
alarms are necessary when the system can detect incipient failures in time to
take such corrective action. Training is probably next most important after
design, but any amount of training cannot compensate for an error-prone design.
Preventing exposure to error by guards, locks, or an additional “execute” step
can help make sure that the most critical actions are not taken without
sufficient forethought. Least effective are written warnings such as posted
decals or warning statements in instruction manuals, although many tort lawyers
would like us to believe the opposite.
