Cobra Effect · Learning and memory
The spacing effect
Spread your study out over time and it lasts far longer.
5 cards, read aloud in 1:41, with a test and sources.
1885. A man memorises nonsense for years.
Hermann Ebbinghaus taught himself lists of meaningless syllables and timed how fast he forgot them. He found that forgetting is steep at first and then flattens. He drew it. It is called the forgetting curve.
He also found the cure, by accident.
Reviewing a list once, just before you would have forgotten it, made the next forgetting slower. Review again a little later, and slower still. Each review pushes the curve flatter.
Cramming works for tomorrow and fails for next month.
Ten hours the night before produces a high score and a fast forgetting curve. The same ten hours spread over three weeks produces a slightly lower score and a curve that barely moves. For an exam in a month, spread wins by a mile.
It is one of the most replicated findings in psychology.
A hundred and forty years of studies, across ages, subjects and languages. It works for facts, for skills and for languages. It is also almost never how anyone studies.
So put your revision on a schedule, not a pile.
A fact you know should come back in a few days, then a week, then a month. A fact you missed should come back tomorrow. You are not repeating yourself. You are meeting the fact again just before you would have forgotten it.
Sources
- Memory: A Contribution to Experimental Psychology, Hermann Ebbinghaus, 1885. The book of the nonsense syllables, in its 1913 English translation. Search the English title. Ebbinghaus’s Wikipedia page describes the method and the curve.
- Make It Stick, Peter Brown, Henry Roediger and Mark McDaniel, 2014. The spacing research turned into practice by two of the researchers who did it. Roediger’s Wikipedia page lists it among his work.
- Spacing effect, Wikipedia. The finding, the theories of why it works, and the size of the evidence behind it, with the meta analyses cited.
Nearby ideas
- The Dunning Kruger effect. Why the least skilled are often the worst judges of their skill.
- Regression to the mean. Extreme results drift back towards normal, whatever you do.
- Parkinson’s law. Work expands to fill the time you give it.
- The testing effect. Pulling an answer from memory teaches more than reading it again.
- Desirable difficulties. The practice that feels hardest is often the practice that sticks.
- Interleaving. Mixing problem types feels worse and teaches better.
- The Feynman technique. If you cannot explain it simply, you have found a gap.
- Chunking. Experts see patterns where beginners see pieces.