The document discusses Hermann Ebbinghaus's work on the forgetting curve. It explains that according to Ebbinghaus, people forget about 60% of new meaningless information within the first 20 minutes, and that most forgetting occurs within the first 8 hours. It then discusses techniques to improve memory retention like ensuring information is meaningful, learned over time, and well encoded. Finally, it compares different measures of memory retention - recall, recognition, and relearning - explaining that recognition and relearning are more sensitive measures of retained information than recall.