Human Performance Fundamentals and Error Mechanisms
Core concepts
Human performance in a control room is best understood as the product of capability, context, and constraint. Candidates must distinguish skill-based, rule-based, and knowledge-based performance (Rasmussen) and match error types to them: slips and lapses dominate skill-based work, rule-based work produces misapplied or wrong rules, and knowledge-based work yields biases and faulty mental models. Learn the Generic Error-Modelling System (GEMS) and Swiss-cheese defence model, plus the distinction between active failures (front-line acts) and latent conditions (design, maintenance, procedures, training).
Also know error-producing conditions (time pressure, poor interface, ambiguous cues, fatigue, low manning), violations versus errors (intentional deviation, often driven by perceived work pressure), and the performance-shaping factors used in human reliability analysis. Situation awareness (Endsley's perception-comprehension-projection) and cognitive lockup (perseveration on a failing strategy) recur in incident narratives.
Traps in questions
- Equating error with carelessness; most errors are systematic and predictable from context.
- Confusing a slip (right intention, wrong execution) with a mistake (wrong intention or plan).
- Treating a violation as necessarily reckless; routine violations often reflect normalised drift.
- Assuming more automation removes error; it shifts it to monitoring and mode-awareness failures.
- Confusing latent conditions with root causes in investigation language.
Worked rule of thumb
When classifying an event, ask three questions in order: Was the intention correct? If yes and execution failed, it is a slip or lapse. If the intention itself was wrong but a rule existed, it is a rule-based mistake; if no adequate rule existed, it is a knowledge-based mistake. Then ask whether a latent condition made that error more likely. Example: an operator correctly intends to close valve B but operates the adjacent, identically labelled valve C. Intention was right, action wrong, layout supported the slip - a skill-based slip with a latent design condition, not a knowledge failure.