In some contexts, errors are dichotomized as slips or mistakes, based on the cognitive psychology of task-oriented behavior. Mistakes reflect failures during attentional behaviors; behavior that requires conscious thought, analysis, and planning, as in active problem solving. 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 heuristic or rule. Thus, choosing the wrong diagnostic test or ordering a suboptimal medication for a given condition represents a mistake. Mistakes often reflect lack of experience or insufficient training. Reducing the likelihood of mistakes typically requires more training, supervision, or occasionally disciplinary action (in the case of negligence).

Unfortunately, health care has typically responded to all errors as if they were mistakes, with remedial education and/or added layers of supervision. In point of fact, most errors are actually slips, which are failures of schematic behavior that occur due to fatigue, stress, or emotional distractions, and are prevented through sharply different mechanisms.