A broad issue in cognitive systems engineering is at stake here. If we want to learn from practitioners’ interactions with each other and technology, we need to study their practice. Process tracing methods are part of a larger family of cognitive task analysis but aim specifically to analyze how people’s understanding evolved in parallel with the situation unfolding around them during a particular problem-solving episode. Process tracing methods are extremely useful, if not indispensable, in the investigation of incidents and accidents.