The need for communication and synchronization of actions among members
of a team is a very subtle phenomenon. The large mechanical controls and the
resulting large control rooms required people to move around a lot as they did
their tasks. As a result, a lot of communication was shared, but invisibly, acci-
dentally, without people really being aware that it was happening. Nobody
realized just how important this was to the smooth operation of the system
untilitwentaway.
Asimilar situation was observed when my colleague Edwin Hutchins
studied the navigation procedures used in large ships in the United States
Navy. Members of the navigation team communicated with one another
through telephone handsets, so each could hear what the others were saying.
The person taking bearings of landmarks from the port side of the ship could
hear the person taking bearings off the starboard side. The chief and the plot-
ters heard everything. Periodically there were errors. The bearer takers were
instructed to look for inappropriate landmarks, or the readings were reported
or recorded wrong. When equipment broke down, manual corrections had to
be applied to the readings given by the magnetic compasses, and during the
initial stages of the breakdown, when everyone was under some stress and
time pressure, more errors were made.
Thenormalresponseofthecognitivescientisttothebabbleofvoicesoverthe
telephone sets and the prevalence of error is to try to simplify things, to get rid
of the error. Maybe the telephone lines should be connected individually to
each member of the team so they wouldn’t have to listen to all that irrelevant
stuff from the other people. The error rate certainly ought to be worked on:
Error can’t be a good thing. Wrong.
Hutchins showed that the shared communication channel and, especially, the
shared hearing of the errors was critical to the robustness and reliability of the
task. Anavigation team is a permanent fixture of a ship, but the individual
members of the team are continually changing. At any one time, the team is
composed of individuals who vary in skill from novices to accomplished ex-
perts. The shared communication keeps them all informed. The shared listening
to the errors and the corrections acts as an informal, but essential, training
program, one that is operating continually and naturally, without disrupting
the flow of activity. In fact, two different kinds of people are being trained
simultaneously. It is obvious that the person who made the error is being
trained. It is not so obvious that the rest of the crew is also learning from
the event: The less experienced crew members learn by hearing of the error
and listening to the correction activities; the more experienced crew members
are learning how to train, noting what kinds of error correction and feedback
are effective, what kinds are disruptive. Over the years, as the shipmates
change which part of the task they are responsible for, as some members
leave and new ones join, this shared communication channel, with its shared
teaching and correcting process, keeps everyone at a uniformly high level of
expertise.
The unplanned properties of the large control rooms that enhance social
communication and the training roles played by the detection and correction of
errors teach several lessons. The most important deal with the nature of shared
work, shared communication. These are subtle activities, and we still know re-
446 Donald A. Norman