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Home›Psychology

Memory

How memory is stored, why it fades, and what the research says about remembering more: the forgetting curve, spaced repetition, retrieval practice, sleep and false memories, with this site's flashcards as the lab.

Progress

About this course

Hermann Ebbinghaus was his own and only subject. To avoid words that already carried meaning, he built syllables of consonant, vowel, consonant that were not words, 13 of them to a row. He read a row aloud at a steady pace until he could recite it without error, and he timed the whole effort. Then he waited 20 minutes, a day, six days or 31 days, learned the same row again and timed that too. After 20 minutes he saved 58.2% of the work, and after 31 days 21.1%. That is the forgetting curve, and it is where the course turns from describing memory to improving it.

The six units start with sensory, working and long-term memory. In 1960 George Sperling flashed 12 letters, people could name only about four, yet a tone after the letters vanished showed about nine were still there. Spaced repetition cites a 2006 review of 839 tests of spacing in 317 experiments, in which the same total study time works better split into sessions. Retrieval practice describes Roediger and Karpicke's 2006 study: a week later, students who tested themselves three times recalled 61%, against 40% for rereading three times. Sleep and memory covers Jenkins and Dallenbach in 1924, whose two colleagues forgot less after sleep. The last unit shows that people who heard "smashed" instead of "hit" judged a filmed car crash as faster. The site's own flashcards serve as the lab.

Before you start

You can start here directly. Each idea is introduced through a named study, such as Sperling's letter grid or Ebbinghaus's nonsense syllables. If you want to know how memories are held in the brain, Brain and nerves gives the background, and the sleep unit links to it.

When you finish

Once done, you can tell sensory, working and long-term memory apart, read a forgetting curve and calculate Ebbinghaus's savings score, and plan reviews with spaced repetition. You can explain why testing yourself beat rereading in the retrieval study, what sleep does for remembering, and how the word smashed changed what people later recalled about a car crash.

  1. 1Sensory, working and long-term memoryIn 1960 George Sperling flashed 12 letters for a split second. People could name only about four, yet a tone played after the letters vanished showed that about nine were still there.
  2. 2The forgetting curveHermann Ebbinghaus learned rows of 13 nonsense syllables and timed how long relearning took. After 20 minutes he saved 58.2% of the work; after 31 days, 21.1%.
  3. 3Spaced repetitionA 2006 review found 839 tests of spacing in 317 experiments. The same total study time works better split into sessions with gaps between them.
  4. 4Retrieval practiceA week after reading a passage, students who had tested themselves three times recalled 61% of it. Students who had reread it three times recalled 40%.
  5. 5Sleep and memoryIn 1924 two Cornell researchers had two colleagues learn nonsense syllables and then either sleep or stay awake. After sleep they forgot less.
  6. 6Memory illusions and false memoriesPeople who heard the word "smashed" instead of "hit" later judged a filmed car crash as faster, and more than twice as many claimed to have seen broken glass that was never there.

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Sources for this course (16)
  • OpenStax Psychology 2e (openstax.org/books/psychology-2e)
  • sections 8.1 How Memory Functions (Atkinson and Shiffrin 1968; Baddeley and Hitch 1974; Miller 1956; Cowan 2010; Peterson and Peterson 1959; Keppel and Underwood 1962; Tulving 1972)
  • 8.2 Parts of the Brain Involved with Memory (H. M.)
  • 8.3 Problems with Memory (Ebbinghaus 1885; Schacter 2001 seven sins; Loftus and Palmer 1974; proactive and retroactive interference)
  • 8.4 Ways to Enhance Memory, 4.3 Stages of Sleep. Sperling (1960) Psychological Monographs 74(11) (sites.socsci.uci.edu/~whipl/staff/sperling/PDFs/Sperling_PsychMonogr_1960.pdf): 12 symbols, 76% partial report, about 9.1 letters, whole report slightly over four. Ebbinghaus (1885/1913) savings 58.2% at 20 min, 44.2% at 1 h, 35.8% at 8.8 h, 33.7% at 1 day, 27.8% at 2 days, 25.4% at 6 days, 21.1% at 31 days
  • Murre and Dros (2015) PLoS ONE 10(7) e0120644 replication (one subject, 70 hours, rows of 13 syllables)
  • Cepeda et al. (2006) Psychological Bulletin, PubMed 16719566 (839 assessments, 317 experiments, 184 articles)
  • Cepeda et al. (2008) Psychological Science 19(11)
  • PubMed 19076480 (more than 1,350 people, gap up to 3.5 months, test up to 1 year, optimal gap about 20 to 40% of a 1-week delay and 5 to 10% of a 1-year delay)
  • Roediger and Karpicke (2006) Psychological Science 17(3) 249-255 (Experiment 2: 5-min test SSSS 83%, SSST 78%, STTT 71%; 1-week test STTT 61%, SSST 56%, SSSS 40%)
  • Dunlosky et al. (2013) PSPI 14(1)
  • PubMed 26173288. Jenkins and Dallenbach (1924) American Journal of Psychology 35, 605-612 (two colleagues, nonsense syllables, 1 to 8 hours)
  • Sara (2017) J Neurosci review, PMC6596760 (Rasch and Born 2013, 1,358 references)
  • Journal of Sleep Research (2021) 10.1111/jsr.13042 "Evidence against a large effect of sleep in protecting verbal memories from interference". Roediger and McDermott (1995) JEP:LMC 21 (false recall 40% with 12-word lists, 55% with 15-word lists)
  • Card intervals in the hands-on parts come from this site's own flashcard code (boxes 0 to 5, 0, 1, 3, 7, 14, 30 days)
  • Everyday scenes are made up for teaching. General information only, not medical advice.

Checked: 2026-10-17