Human Error and Biases

Human Error - Definition  An inappropriate or undesirable human decision or behavior that reduces, or has the potential for reducing, effectiveness, safety, or system performance.  An undesirable effect or potential effect on systems or people.  An error that is corrected before it can cause damage is an error nonetheless.

Error Classification Discrete Action  Omission - Forgetting to do something, or just deliberately ignoring it.  Commission - Performing an act incorrectly.  Sequence - Right action, wrong order.  Timing / Rate - Too fast or too slow.

Error Classification Information Processing Specific error categories at each stage of information processing.  1. Observation of system state  2. Choice of hypothesis  3. Testing of hypothesis  4. Choice of goal  5. Choice of procedure  6. Execution of procedure

Error Classification Information Processing - continued The errors depend on the level of behavior.  1. Skill-based behavior  2. Rule-based behavior  3. Knowledge-based behavior

Error Reduction Selection  Selection of personnel with skills and capabilities (perceptual, intellectual, motor skills, etc.)  Limitations 1. Not easy to determine skills required. 2. Few reliable tests for measuring skill levels. 3. Limited supply of qualified people.

Error Reduction Training  Proper training of personnel reduces errors.  Limitations  Old habits are hard to break.  Training can be expensive.

Error Reduction Design  Exclusion Particular errors made impossible to commit  Prevention Particular errors made difficult to commit  Fail-safe Consequences of errors reduced in severity

Human Biases People give an undue amount of weight to early evidence or information. Humans are generally conservative and do not extract as much information from sources as they optimally should. The subjective odds in favor of one alternative or the other are not assessed to be as extreme or given as much confidence as optimally they should.

Human Biases - continued As more information is gathered, people become more confident in their decisions, but not necessarily more accurate. Humans have a tendency to seek far more information than they can absorb adequately. People often treat all information as if it were equally reliable.

Human Biases - continued People cannot entertain more than a few (three or four) hypotheses at a time. People tend to focus on only a few critical attributes at a time and consider only about two to four possible choices that are ranked highest of those few critical attributes. People tend to seek information that confirms the chosen course of action and to avoid information or tests whose outcome could disconfirm the choice. (Confirmation Bias)

Human Biases - continued A potential loss is viewed as having greater value than a gain of the same amount. (Risk Aversion) People believe that mildly positive outcomes are more likely than either mildly negative or highly positive outcomes. People tend to believe that highly negative outcomes are less likely than mildly negative outcomes.