COCOM.
Contextual Control Model
Originator Erik Hollnagel (1993)
Paradigm Cognitive systems engineering
Unit of analysis Control of action in context
Primary domains Aviation, process control, rail, medicine

COCOM models the operator as a cyclical controller of action whose behaviour depends on how much control context allows — ranging from chaotic reactivity to strategic planning. It is the cognitive foundation beneath CREAM and the precursor to ECOM.

Overview of the framework

Hollnagel (1993) proposed COCOM as a pragmatic alternative to stepwise information-processing models. Cognition is treated as control of a joint cognitive system: the operator continuously constructs and updates an understanding of the situation, selects next actions, and revises plans based on feedback. The model distinguishes four control modes — scrambled (random, dominated by time pressure), opportunistic (trial-and-error, salient cues), tactical (rule- and procedure-based, short horizon), and strategic (goal-directed, long horizon) — ordered by the breadth of what the operator considers and the reliability of the resulting action. Which mode is in use depends on time available, number of goals, information available, mode of execution and the subjectively available resources. COCOM reframes "human error" as an outcome of mismatched control rather than an inherent failure.

Events/Feedback (environment) Construct situation model Select action next step / plan Execute Four Control Modes Scrambled — random, time-pressured Opportunistic — salient cues, trial & error Tactical — rules & procedures, short horizon Strategic — goal-directed, long horizon less control · less reliable more control · more reliable Context determines mode time · # goals · information · execution mode
Figure 1. COCOM's cyclic model of action control (left) and the ladder of four control modes (right). Context determines which mode is active; the mode determines reliability.

When to use it

Typical applications

  • Foundational model for cognitive task analysis and CREAM-based HRA.
  • Design of decision-support tools and alerts that preserve tactical/strategic control.
  • Framing of incidents where operators were forced into opportunistic or scrambled modes.
  • Teaching aid in crew resource management (CRM) training.

Aviation relevance

  • Useful in analysing time-critical flight-deck events (rejected take-off, TCAS RA, upset recovery).
  • Explains how automation mode confusion can push crews from tactical to opportunistic control.
  • Cross-domain: process control, anaesthesia, emergency medicine, rail operations.

Benefits

Analytical strengths

  • Treats cognition as control, not as a queue of information-processing stages.
  • Makes context and control mode central to explanations of performance.
  • Captures cyclical rather than linear behaviour — closer to observed crew performance.
  • Provides a common vocabulary linking training, design and HRA.

Practical strengths

  • Foundation for CREAM, ECOM and the Resilience Engineering programme.
  • Simple enough to use as an educational framework with practitioners.
  • Supports Safety-II framing of everyday adaptive performance.

Limitations

  • Qualitative. COCOM by itself does not produce probabilities or risk numbers — quantification is added in CREAM.
  • Coarse discretisation. Only four control modes; real performance is more graded.
  • Model boundary is individual/crew. Limited in handling organisational and inter-team dynamics (addressed in ECOM and Joint Cognitive Systems).
  • Assessment depends on observation: identifying the active control mode in the field is non-trivial.
In short COCOM is the cognitive engine beneath modern second-generation HRA and resilience engineering. Its enduring contribution is the reframing of human behaviour as context-dependent control rather than inherent (un)reliability.

References (APA 7)

Hollnagel, E. (1993). Human reliability analysis: Context and control. Academic Press.

Hollnagel, E. (1998). Cognitive reliability and error analysis method (CREAM). Elsevier Science.

Hollnagel, E. (2002). Cognition as control: A pragmatic approach to the modelling of joint cognitive systems. IEEE Transactions on Systems, Man, and Cybernetics: Part A, 32(2), 185–197. https://doi.org/10.1109/TSMCA.2002.1021104

Hollnagel, E., & Woods, D. D. (2005). Joint cognitive systems: Foundations of cognitive systems engineering. CRC Press. https://doi.org/10.1201/9781420038194

Woods, D. D., & Hollnagel, E. (2006). Joint cognitive systems: Patterns in cognitive systems engineering. CRC Press.

Further reading

Hollnagel, E. (2004). Barriers and accident prevention. Ashgate.

Rasmussen, J. (1983). Skills, rules, and knowledge; signals, signs, and symbols, and other distinctions in human performance models. IEEE Transactions on Systems, Man, and Cybernetics, SMC-13(3), 257–266.

Klein, G. (1998). Sources of power: How people make decisions. MIT Press.

Vicente, K. J. (1999). Cognitive work analysis: Toward safe, productive, and healthy computer-based work. Lawrence Erlbaum.

Hollnagel, E. (n.d.). COCOM [author's site]. https://erikhollnagel.com/ideas/cocom.html