Human Error and BiasesHuman Error and Biases

Human Error - DefinitionHuman 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 ClassificationError ClassificationDiscrete ActionDiscrete 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 ClassificationError ClassificationInformation ProcessingInformation 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 ClassificationError ClassificationInformation Processing - continuedInformation Processing - continued

The errors depend on the level of behavior. 1. Skill-based behavior 2. Rule-based behavior 3. Knowledge-based behavior

Error ReductionError ReductionSelectionSelection

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 ReductionError ReductionTrainingTraining

Proper training of personnel reduces errors.

Limitations Old habits are hard to break. Training can be expensive.

Error ReductionError ReductionDesignDesign

Exclusion Particular errors made impossible to commit

Prevention Particular errors made difficult to commit

Fail-safe Consequences of errors reduced in severity

Human BiasesHuman Biases People give an undue amount of weight to early

evidence or information.

Humans are generally conservative and do notextract as much information from sources asthey optimally should.

The subjective odds in favor of one alternative orthe other are not assessed to be as extreme orgiven as much confidence as optimally they should.

Human Biases - continuedHuman 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 moreinformation than they can absorb adequately.

People often treat all information as if it wereequally reliable.

Human Biases - continuedHuman Biases - continued People cannot entertain more than a few

(three or four) hypotheses at a time.

People tend to focus on only a few criticalattributes at a time and consider only abouttwo to four possible choices that are rankedhighest of those few critical attributes.

People tend to seek information that confirmsthe chosen course of action and to avoidinformation or tests whose outcome coulddisconfirm the choice. (Confirmation Bias)

Human Biases - continuedHuman Biases - continued A potential loss is viewed as having greater

valuethan 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.