How quickly do we forget things and can the forgetting curve be beaten?

The answer

Hermann Ebbinghaus discovered the forgetting curve in 1885, demonstrating that memory retention drops exponentially: approximately 56% of new information is forgotten within one hour, 70% within 24 hours, and 90% within one week without reinforcement. However, spaced repetition - reviewing material at increasing intervals - dramatically flattens this curve. A 2019 meta-analysis confirmed that spacing study sessions produces 10-30% better long-term retention than massed practice. The optimal intervals follow an expanding schedule: review after 1 day, then 3 days, then 7 days, then 21 days. Each retrieval strengthens the memory trace through reconsolidation, making it more resistant to decay. Modern spaced repetition software like Anki uses algorithms based on Piotr Wozniak's SuperMemo model to calculate personalized optimal review timing for each individual fact.