Memory researchers certainly haven’t forgotten Hermann Ebbinghaus, the first person to do scientific studies of forgetting, using himself as a subject. He spent a lot of time memorizing endless lists of nonsense syllables and then testing himself to see whether he remembered them. He found that he forgot most of what he learned during the first few hours after learning it.
Later researchers have found that forgetting doesn’t always occur that quickly. Meaningful information fades more slowly than nonsense syllables. The rate at which people forget or retain information also depends on what method is used to measure forgetting and retention. Retention is the proportion of learned information that is retained or remembered—the flip side of forgetting.
Researchers measure forgetting and retention in three different ways: recall, recognition, and relearning.
Recall is remembering without any external cues. For example, essay questions test recall of knowledge because nothing on a blank sheet of paper will jog the memory.