CONCEPT
The Pattern Library
Klein's term for the accumulated repository of recognized situations and their associated features, actions, and expected outcomes — an organic cognitive structure that grows through experience and degrades through disuse.
The pattern library is the experiential foundation on which expert cognition depends. It is not a database but a dynamic cognitive structure, built case by case through direct engagement with a domain, refined through feedback, and maintained only through ongoing practice. Every fire the commander attends deposits patterns. Every patient the nurse treats refines the model. The library's richness determines the expert's capacity for the three functions that distinguish expert from novice performance: anomaly detection, mental simulation, and sensemaking. No two experts have identical pattern libraries because no two have identical experiential histories. The library's enemies — prolonged absence from practice, abstract training substituted for direct engagement, and now the automation of the tasks that provide experiential raw material — are the conditions under which expertise atrophies faster than it accumulates.
In The You On AI Field Guide
Klein's NICU nurse Darlene illustrates the pattern library's stakes. She paused at an infant whose monitors showed normal readings, sensed something