Human Error

Theoretical and methodological developments within the field of cognitive psychology have made it possible to better understand mental processes, explain some of the predictable manifestations of human fallibility, and develop effective strategies to eliminate or reduce human errors in complex systems. Canadian Patient Safety Dictionary defines human error as the failure to complete a planned action as it was intended, or when an incorrect plan is used in an attempt to achieve a given aim. A number of different human error taxonomies are used retrospectively to analyze accidents for root causes, identify system weaknesses and develop countermeasures, as well as prospectively to predict and prevent possible errors in the future. However, the lack of consensus regarding the definition of error represents considerable challenges in the effort to detect, minimize or eliminate errors across different work environments. Much of the practical knowledge that has been accumulated on human error is derived from industries capable of producing catastrophic events with enormous loss of human life. Recognition of human error has strongly influenced the system design, reliability and risk management programs that are essential for the success of many organizations with potentially hazardous technologies. While human errors and adverse events occurring within the healthcare system are numerous, serious and insidious, they do not culminate in dramatic catastrophes such as the Chernobyl nuclear accident or Bhopal chemical plant disaster. Research data suggest that human error, not technical malfunction, is the primary cause of 60 to 90% of major accidents in aviation, chemical processing, healthcare, and other complex high-risk systems. It is increasingly recognized that many accidents involving human errors are caused by human-system interface problems and significant mismatch between task demands and human mental and physical capabilities. The figure below provides classification of errors based on the Skills, Rules, Knowledge (SRK) framework that differentiates between skill-based, rule-based, and knowledge-based levels of human performance.


Error Types


Slips and lapses occur almost invariably due to distractions while performing routine or automatic tasks. Any unwanted consequences resulting from slips and lapses can be attributed to an error arising from an unintentional action. When it comes to mistakes, the actions proceed as intended but they do not accomplish their intended outcome. Any unwanted consequences resulting from mistakes can be attributed to an error arising from intended but mistaken actions. However, adverse outcomes are not always directly associated with unintentional or mistaken actions. Chance alone may sometimes be the only factor that separates actual accidents from near misses that have no apparent negative consequences. Acts of sabotage or intentional violations of safety procedures are not generally classified as human error, particularly when the actions are carried out as planned without creating unforeseen and unsafe conditions. Erroneous actions associated with formal training programs, innovation and experimentation under controlled conditions should also be excluded from the definition of human error. It is not always easy to determine and classify human errors, particularly when carrying out a retrospective analysis of information in a patient’s chart or incident report. For example, administering the wrong dose of antibiotic may constitute:

  1. Slip – Unintentionally giving the wrong dose due to a failure of attention caused by distraction while preparing the drug
  2. Mistake – Intentionally giving the wrong dose due to lack of knowledge regarding the correct dose for a patient with a specific medical condition
  3. Violation – Intentionally giving the wrong dose based on personal opinion that a prescribed dose may not provide adequate treatment

Classification of errors becomes even more difficult when employees take shortcuts to improve speed and productivity or when existing rules, policies and procedures are considered inappropriate for the given situation.