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278 Adaptation

a considerable extent on knowing what not to do: Do not take off in a snow-
storm without properly de-icing the wings; do not underestimate the enemy;
do not ignore differences in corporate culture when considering a merger;
do not ignore counterindications to the most frequently encountered med-
ical diagnosis; and so on. In general, safety rules are norms, and norms are
constraints by another name.
The application of constraints depends on information about the current
state of the system, in both individuals and collectives. The unique difficulty that
appears at the collective level is that in a complex system, no single operator
knows all the constraints, and no single operator has access to all the information
about the current system state. How, then, do collectives decide that some con-
straint has been violated and that the system has slid onto a pre-failure track?
One emergent mechanism at the collective level is that different individu-
als play different roles, some providing information, others applying constraints.
Consider the navigation of a large ship in and out of the San Diego harbor. The
harbor is connected to the sea through a long, narrow and winding channel.
When a large ship like a military aircraft carrier enters or exits the harbor, the
navigating team’s need to know the exact position of the ship at each moment in
time is acute. If a turn is initiated too late, there is a possibility that the momen-
tum of the massive ship will carry it past the turn and onto the opposite shore.
Edwin Hutchins, a cognitive scientist trained as an anthropologist, obtained per-
mission to travel on a U.S. Navy carrier and observe the operation of the naviga-
tion team – the Sea and Anchor Piloting Detail in navy terminology – that plotted
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the successive positions of the ship on a sea chart. The position of the ship on the
chart is determined by taking two or three simultaneous compass bearings from
the ship to prominent and recognizable landmarks on both sides of the ship, such
as a lighthouse or some prominent landscape feature. The bearings are reported
to a plotting team inside the bridge, the control and command center of a ship,
and drawn as straight lines on the sea chart. The point on the chart at which the
lines cross each other (and the line representing the ship’s course) is the position
of the ship at the point in time when the bearings were taken.
As Hutchins reports in his 1995 book Cognition in the Wild, there are multi-
ple possibilities for error. The two seamen on either side of the bridge who take
the compass bearings – the pelorus operators – might mistake one landmark
for another, fail to read the two bearings at exactly the same moment, read
a bearing incorrectly on their instruments or speak it incorrectly when they
report it to the plotting team. The members of the plotting team might hear
a bearing incorrectly or plot it incorrectly. Nevertheless, aircraft carriers do
not run aground. The operating procedures of the Sea and Anchor Detail have