Human error is an action that has been done but that was "not intended by the actor; not desired by a set of rules or an external observer; or that led the task or system outside its acceptable limits". Human error has been cited as a primary cause and contributing factor in disasters and accidents in industries as diverse as nuclear power (e.g., the Three Mile Island accident), aviation (e.g., United Airlines Flight 173), space exploration (e.g., the Space Shuttle Challenger disaster and Space Shuttle Columbia disaster), and medicine. Prevention of human error is generally seen as a major contributor to reliability and safety of (complex) systems. Human error is one of the many contributing causes of risk events.
Contents
Definition
Human error refers to something having been done that was "not intended by the actor; not desired by a set of rules or an external observer; or that led the task or system outside its acceptable limits". In short, it is a deviation from intention, expectation or desirability. Logically, human actions can fail to achieve their goal in two different ways: the actions can go as planned, but the plan can be inadequate (leading to mistakes); or, the plan can be satisfactory, but the performance can be deficient (leading to slips and lapses). However, a mere failure is not an error if there had been no plan to accomplish something in particular.
Performance
Human error and performance are two sides of the same coin: "human error" mechanisms are the same as "human performance" mechanisms; performance later categorized as 'error' is done so in hindsight: therefore actions later termed "human error" are actually part of the ordinary spectrum of human behaviour. The study of absent-mindedness in everyday life provides ample documentation and categorization of such aspects of behavior. Having a sense of awareness is needed to understand when dealing with a potential danger, thus being able to correct it. While human error is firmly entrenched in the classical approaches to accident investigation and risk assessment, it has no role in newer approaches such as resilience engineering.
Categories
There are many ways to categorize human error:
exogenous versus endogenous error (i.e., originating outside versus inside the individual)
situation assessment versus response planning and related distinctions in
error in problem detection (also see signal detection theory)
error in problem diagnosis (also see problem solving)
error in action planning and execution (for example: slips or errors of execution versus mistakes or errors of intention)
by level of analysis; for example, perceptual (e.g., optical illusions) versus cognitive versus communication versus organizational
physical manipulation error
'slips' occurring when the physical action fails to achieve the immediate objective
'lapses' involve a failure of one's memory or recall
active error - observable, physical action that changes equipment, system, or facility state, resulting in immediate undesired consequences
latent human error resulting in hidden organization-related weaknesses or equipment flaws that lie dormant; such errors can go unnoticed at the time they occur, having no immediate apparent outcome
equipment dependency error – lack of vigilance due to the assumption that hardware controls or physical safety devices will always work