HUMAN ERROR AND HUMAN PERFORMANCE

HUMAN ERROR AS A SOURCE OF RISK There are three major causes of risk: Hardware failures Human error Natural disasters So far, we’ve analyzed only hardware failures However, over time, hardware has become more reliable: And technology is getting more powerful and complex So, human error is now a larger share of the total risk 2

HUMAN ERROR AS A SOURCE OF RISK Moreover, studies of major accidents show similarities in the types of human errors that are involved: “Random error…is not the issue” Situations can predispose people to make errors Bley (2002) identifies the following predisposing factors: “Operation outside designer’s intention” “Resulting physical regime not well understood” “Operators refuse to believe or recognize…evidence” “Prepared plans are not applicable or helpful” Links and Notes: Bley, D. (2002). “New Methods for Human Reliability Analysis,” Environmental Management and Health, Vol. 13, No. 3, pp. 277-289, http://www.emeraldinsight.com/Insight/ViewContentServlet?Filename=/published/emeraldfulltextarticle/pdf/0830130305.pdf. 3

EXAMPLE Historically, Chernobyl considered inapplicable to U.S.: No containment Graphite moderator Bley (2002) identified common operational issues: Three Mile Island Chernobyl Work-around Intentional circumvention Lack of understanding of implications Lack of understanding in unusual situation Continued refusal to believe implications of instruments Continued refusal to believe instruments, field reports Links and Notes: Bley, D. (2002). “New Methods for Human Reliability Analysis,” Environmental Management and Health, Vol. 13, pp. 277-289, http://www.emeraldinsight.com/Insight/ViewContentServlet?Filename=/published/emeraldfulltextarticle/pdf/0830130305.pdf. 4

BASIC TYPES OF BEHAVIOR Skill-based (automatic, reflexive): Playing an instrument Driving a car Rule-based: Following a pre-specified rule or procedure Knowledge-based: Reasoning from one’s basic knowledge Links and Notes: Rasmussen, J. (1986). Information Processing and Human-Machine Interaction: An Approach to Cognitive Engineering, Elsevier Science Ltd., New York, NY. 5

BASIC TYPES OF BEHAVIOR Over time, nuclear power has become more rule-based: And less knowledge-based Three Mile Island showed that operators may not find the right answer in a timely manner from basic knowledge However, we may now be overly rule-based: Leading to loss of broader “situational awareness” 6

ERRORS ASSOCIATED WITH BEHAVIOR TYPES Skill-based errors: Slips and lapses (driving home instead of to store) Rule-based mistakes: Misapplication of good rules Application of bad rules Knowledge-based mistakes: Misdiagnosis (e.g., due to instrument errors) Insufficient or incorrect domain knowledge Time pressure (e.g., on a calculus exam) Links and Notes: Reason, J. (1990). Human Error, Cambridge University Press, New York, NY, http://books.google.com/books?id=WJL8NZc8lZ8C&pg=PA53&dq=james+reason+slips+lapses+human+error&client=firefox-a&sig=F39dTeu4TSBWnk6r3d1XXLJVFFM. 7

ERRORS ASSOCIATED WITH BEHAVIOR TYPES Some designs are much better than others: Easy to recognize Difficult to recognize However, with skill-based (reflexive) behavior: Someone who is used to the poor design may be prone to errors when using the “better” design Especially under time pressure or emergencies 8

ERRORS OF OMISSION AND COMMISSION Necessary action is not taken Errors of commission: Undesirable action is taken Historically considered impossible to analyze 9

ERRORS OF COMMISSION However, Macwan and Mosleh (1994) argued that most errors of commission are in principle predictable: Intentional skips (task viewed as unnecessary) Short cuts (taking the path of least resistance) Misdiagnosis (resulting in a sequence of errors) Delayed actions (e.g., due to conflicting goals) Links and Notes: Macwan, A., and A. Mosleh (1994). “A Methodology for Modeling Operator Errors of Commission in Probabilistic Risk Assessment,” Reliability Engineering and System Safety, Vol. 45, pp. 139-157 10

FACTORS PREDISPOSING TO ERROR Because most serious errors have complex causes: Bley (2002) refers to unsafe actions, not errors Action may not have seemed like an error at the time Predisposing factors: Plant conditions (work-around, circumvention) Performance shaping factors (fatigue, poor training) Error mechanisms (Thompson et al., 1997): “Not inherently bad behaviors but…allow humans to perform skilled and speedy operations” Links and Notes: Thompson, C. M., et al. (1997). “The Application of ATHEANA: A Technique for Human Error Analysis,” http://ieeexplore.ieee.org/iel3/4930/13600/00624860.pdf. 11

HUMAN BEHAVIORAL TECHNOLOGY People do what they’ve done before People do what they see others do People don’t do what they can’t do Behavior is a function of consequence Behavior is a function of structure Behavior is elicited by antecedents Experience makes an antecedent out of an item Reinforcement increases frequency Reinforcement works until it saturates Punishment decreases frequency Punishment elicits only its avoidance Null consequences are punishment for functional behavior Null consequences are reinforcement for dysfunctional behavior Links and Notes: Corcoran, W. R. (1999, 2004). The Firebird Forum, Vol. 2 (No. 5) and Vol. 7 (No.11), available on request from firebird.one@alum.MIT.edu. 12