Our current understanding of human practitioner cognition grew out of the experience of the Three Mile Island (TMI)nuclear reactor meltdown, March 1979.
This dramatic event showed that safe operation of complex systems could only be obtained if (1) the operators were able to comprehend the range of possible meanings of data during an accident and (2) the operators had opportunities to influence the evolving accident. Before TMI it was possible to imagine that operators were present to follow the written procedures developed by engineers and designers. After TMI everyone understood that it was essential that operators be able to develop and sustain adequately detailed mental models of what was happening and what the consequences of different actions might be.
TMI launched the modern study of human cognition at work by bringing together a group of psychologists, engineers, and operators to work on the problem of "human error". The following decade produced a revolution in understanding of safety in complex systems. This seminar discusses the accident and the early contributions of Jens Rasmussen. His "Skills, Rules, and Knowledge" paper sets out the problem, the issues involved, and an agenda for research for the 1980's.
What we now think of as safety was born at TMI.
