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In some contexts, errors are categorised as ?slips? or ?mistakes,? based on the cognitive psychology of task-oriented behaviour. Attentional behaviour is characterized by conscious thought, analysis, and planning, as occurs in active problem solving. Schematic behaviour refers to the many activities we perform reflexively or as if acting on ?autopilot.? Complementary to these two behaviour types are two categories of error: slips and mistakes.

Mistakes reflect failures during attentional behaviours, or incorrect choices. Rather than lapses in concentration (as with slips), mistakes typically involve insufficient knowledge, failure to correctly interpret available information, or application of the wrong cognitive rule. Thus, choosing the incorrect process routing on a control panel represents a mistake. A slip, on the other hand, would be forgetting to close a drain valve on that same route.

Distinguishing slips from mistakes serves two important functions. First, the risk factors for their occurrence differ. Slips occur in the face of competing sensory or emotional distractions, fatigue, and stress; mistakes more often reflect lack of experience or insufficient training. Second, the appropriate responses to these error types differ. Reducing the risk of slips requires attention to the designs of protocols, devices, and work environments?using checklists so key steps will not be omitted, reducing fatigue among personnel (or shifting high-risk work away from personnel who have been working extended hours), removing unnecessary variation in the design of key devices, eliminating distractions (eg, phones) from areas where work requires intense concentration, and other redesign strategies. Reducing the likelihood of mistakes typically requires more training or supervision. Even in the many cases of slips, safety management has typically responded to all errors as if they were mistakes, with remedial education and/or added layers of supervision.



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