Human Error The James Reason Model AST 425 AST 425 Dr. Barnhart

Human Error  Human Error study is still in its infancy- much we still don’t understand  Human error in technology breakdown has increased fourfold in 30 years- consequences are increasingly dire

Definitions l Accident or Event Trajectory l Defenses, Barriers, and Safeguards- vary from few to many- from heavily defended to lightly l Unsafe acts- errors and violations l Latent failure- On the “Blunt End” l Active Failure- On the “Sharp”end l Local Trigger- Trips the Event l Event- Complete Penetration of a trajectory- have varying natures from all active (possibly Egypt Air 990 to all latent Columbia- 1 st shuttle disaster)

Error The term “human error” as used herein is composed of two components: -Error Factors- unintended - Violations- intentional

Errors  True errors occur within the mind of an individual and derive mainly from informational problems (forgetting, inattention, incomplete knowledge).

Violations  Violations- occur within a social context and are largely motivational problems such as poor morale, failure to reward compliance and/or sanction Non-compliance

Individual or Collective errors?  The issue of whether accidents are individually caused or collectively caused revolves around three dimensions:  Moral  Scientific  Practical

Moral Issue- much to be gained  Easier to pin legal responsibility on individuals- more direct connection  Issue compounded by professionals willing to accept responsibility- (captain etc.)  Most people highly value personal autonomy- “they should have known better”  We assume big failures result from big mistakes rather than several small ones  Emotional satisfaction in blaming someone

The Scientific Dimension- do we stop with people directly involved or go on back?  Why stop at organizational roots? Why not go back to the beginning of creation?  Answer should be practical- go back so far as to be able to change organizational behavior  Peculiar nature of accidents- initially appear to be the convergence of many failures but we would see the same in any organization frozen in time- why then are failures rare?

What then about the practical?  Moral issue- favors individual approach  Scientific issue- undecided  Answer here depends on two factors:  can latent factors be identified and stopped prior to an accident?  The degree to which improvements can better equip the organization to deal with local failures

Categories of errors and violations  Errors and violations can be categorized into three areas: –Skill based –Rule based –Knowledge based

Errors  Basically there are three types of skill based errors: –Attentional slips- failure to monitor progress of routine actions at some critical point –Memory lapses- forgetfulness (most common) –Perceptual error- misrecognition of some object; we see what we expect to see –Most slips and lapses have minimal consequences; responding “fine” to “hello” etc. but on the flight deck they can be dire!

Rule Based Mistakes  Two types: –Misapplication of good rules- braking to avoid a deer on an icy road; we humans tend to apply solutions to familiar problems on the basis of largely automatic pattern matching –Application of bad rules- learning shortcuts and cutting corners- usually circumstances are forgiving and you “get by with it”

Knowledge based mistakes  Due to Limited capacity of working memory  Incomplete mental models of the problem  Thinking on one’s feet- confirmation bias- bending the facts to fit a hasty conclusion, over-confidence, similarity bias, and frequency bias

Skill-based violations  Corner cutting promoted by a largely indifferent environment

Rule-based violations  More deliberate than skill based violations

Knowledge based violations  Novel circumstance- no specified procedure  Trainers and procedure writers can only address the foreseeable  Usually involve the unexpected occurrence of a rare but trained for situation or an unlikely combination of individually familiar circumstances

To Finish Defining Error  Cicero stated- “To err is human”  Accidents result from a failure of the risk management system to absorb the consequences of these errors (unsafe acts)  Human error is stubborn; sophisticated discrete solutions to human error will likely lead to more sophisticated sources of error- we must be prepared to manage it

The End Questions?