Forgetting curve

A graph of memory retention over time, classically showing rapid initial loss followed by progressively slower forgetting. Its shape depends on the material, learning conditions, and how retention is measured.

Ebbinghaus forgetting function: A mathematical description of retention declining over time, commonly modeled as an exponential function. It formalizes the rapid early decline and slower later loss associated with the classic curve.
Hermann Ebbinghaus: A German psychologist whose experimental work helped establish the scientific study of memory. His self-experiments produced the foundational measurements behind the forgetting curve.
Spaced repetition: A study method that schedules reviews at increasing or optimized intervals. It uses expected forgetting to time reviews before recall becomes difficult.
Forgetting: The loss or inaccessibility of information that was previously learned. The curve is one representation of forgetting, not a complete explanation of it.
Memory consolidation: The processes that stabilize and reorganize newly formed memories over time. Consolidation can make memories less vulnerable to disruption after learning.
Memory: A Contribution to Experimental Psychology: An 1885 book by Hermann Ebbinghaus reporting experiments on learning and memory. It presented the retention findings from which the classic curve became known.
Leitner system: A flashcard scheduling method that moves correctly recalled cards to boxes reviewed less often. Its review intervals turn changing recall strength into a practical study routine.
Memory retention: The persistence of learned information over time. Retention is the quantity plotted on the curve’s vertical axis.
Retrieval practice: Learning through repeated attempts to recall information from memory. Retrieval can strengthen retention and alter the curve compared with passive review.
Nonsense syllable: A pronounceable, unfamiliar syllable used in early experiments to reduce associations with prior knowledge. Ebbinghaus used such material to study forgetting with fewer meaningful-word associations.

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