During an incident, there are never clear clues. Many things are happening at once: workload is high, emotions and stress levels are high. Many things that are happening will turn out to be irrelevant. Things that appear irrelevant will turn out to be critical. The accident investigators, working with hindsight, knowing what really happened, will focus on the relevant information and ignore the irrelevant. But at the time the events were happening, the operators did not have information that allowed them to distinguish one from the other.
( Donald A. Norman )
[ The Design of Everyday Things ]
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