2.1 Human Error

Old view: person approach

Systems are safe but human errors cause accidents

• Focused on human weaknesses: inattention, forgetfulness, moral failings

• Errors in cognitive processing (information processing) • Physiological disorders

New view: system approach

Systems are not safe and human errors are symptoms of deeper problems

• Focus on the system: conditions under which people work, build defense to avert errors or mitigate effects

• Task complexity, error-likely situations, individual differences

Swiss Cheese Model

 A safety model showing how accidents happen when multiple layers of defense (like slices of Swiss cheese) have holes (weaknesses) that line up, allowing hazards to pass through and cause harm.

“holes” in the Swiss Cheese Model

Weaknesses or failures in each layer of defense or safety barrier

a barrier to error propagation

What do the “individual slices of cheese” in the Swiss Cheese Model represent?

when holes in all the defense layers line up, letting a hazard slip through all barriers.

What causes an accident according to the Swiss Cheese Model?

It shows that accidents usually result from multiple small failures, not just one single mistake

 Why is the Swiss Cheese Model important?

Human performance depends on the task and the person’s level of experience.

 What factors influence human performance according to the Taxonomy of Errors?

Skill-based errors

Slips and lapses that happen during automatic tasks — errors in execution when performing familiar actions without much conscious thought.
Norman’s slips of action

ex. typing the wrong letter while typing; forgetting to take medication

Rule-based errors

Errors caused by failing to understand the situation properly. The person is familiar with the task but not experienced enough to automate it or correctly classify the situation

ex. a nurse gives insulin for high-blood pressure without noticing the patient is NPO (nothing by mouth)

Knowledge-based errors

Errors due to lack of knowledge about what to do in an unfamiliar situation. Involves consciously improvising without routines or rules.

ex. junior doctor faces an unknown complication and treats injury without prior knowledge

There is a tendency to assign blame, often on the person who made the error.

What is the common tendency when an error happens?

It suggests the person alone is responsible, ignoring other failures in the system

Why can saying “human error” be misleading?

Hindsight bias

 After knowing the outcome, people believe the error was inevitable and predictable.

 Operators may be less likely to report errors, hiding system flaws that need fixing.

 How can fear of blame affect error reporting?

It ignores underlying system flaws and reduces opportunities to improve safety.

 Why is blaming operators problematic?

Focusing only on eliminating errors might cause overconfidence and miss learning opportunities.

 Why is safety about more than just eliminating errors?

 Errors help with learning and improving systems.

 What positive role can errors play?

Resilience in safety management

 The ability to respond to the unexpected and recover quickly from mishaps.

We want systems to adapt to disturbances and handle unexpected situations.

What do we want systems to do to optimize safety?

 They help reveal specific solutions by identifying types of errors.

How can taxonomies help in remediation?

comprehensive approach

This approach addresses human, team, workplace, and other factors

fallible humans will make future mistakes

expectation about humans in remediation

error-tolerant systems

These systems are designed so human operators can catch and recover their own errors.

error-tolerant systems features

The option to “undo” action

Monitor inputs to confirm the user understands the action.

Provide clear and concise error messages

open-loop system

 A system that does not use feedback

ex. your remote not telling you why your tv isn’t turning on 

closed-loop system

A system that uses feedback to adjust and correct actions.

non-automated: not enough oxygen in the body leads to you breathing heavier

automated: system tells you when to go from next step —> next step

“choking” under pressure

 When skilled performance breaks down in high-pressure situations. Trying too hard or over-focusing on performance.

Focusing on movements can disrupt well-practiced skills and reduce fluidity. (motor skills only)

 How can paying attention affect skilled performance?

Gallwey (1982)

In tennis, focusing too much causes skill to lose fluidity (the "tennis advantage")

Baumeister (1984)

Video game players told to try their best with a supportive audience showed a drop in performance.

Beilock & Carr’s putting test under pressure

 With a large reward and partner depending on them:

• Normal and distracted groups performed worse
  
  

• Self-conscious group performed better

choking on sensorimotor tasks

 Attention to automatic actions interferes with smooth performance.

 Pressure impairs performance only on high working memory questions.

How does choking affect math test performance according to Beilock et al. (2003)

Intrusive or distracting thoughts

 type of thoughts that harm working memory-based performance

Motor performance

 Additional attention harms _______ because you don’t want to think step-by-step

By adapting to environments where performance attention is needed, building resistance to pressure effects.

 How can choking be reduced?