Retrieval practice

The intuition is that you learn by taking information in, and a test only measures what went in. Retrieval practice says the measurement is itself the strongest form of study. Roediger and Karpicke's 2006 experiments put it plainly: students who read a passage once and then recalled it three times, without feedback and without seeing it again, remembered more a week later than students who read it four times. The rereaders had been through the text 14.2 times on average; the testers 3.4 times. Three recall attempts beat four times the exposure. Karpicke and Blunt extended this in Science in 2011: retrieval practice beat concept mapping, the most elaborate form of studying, on inference questions and even when the final test was itself a concept map.

Two things make it work. Retrieval is effortful reconstruction, and rebuilding a memory, rather than recognising it on the page, is what makes the next retrieval easier. It also corrects the picture you have of yourself. In the 2006 study the students who reread four times were the most confident they would remember the passage a week later, and they remembered least. Rereading produces fluency, and fluency feels like knowledge. A test with no feedback, which teaches nothing new, still exposed the gap. In practice this means closing the book and writing down what you know, explaining the idea to someone, or answering the questions before looking at the answers.

The limits are hidden by the headline figure. At a five-minute delay rereading won, 81 against 75 percent, so cramming for a test in the morning is not irrational; the advantage of testing shows up over days. The strongest results come from short prose, word lists and facts. How large the effect is for complex, interconnected material is still argued, and Karpicke and Blunt's paper drew a published comment and a reply in Science. And retrieval without feedback only strengthens what you can already get out. For material you never learned in the first place, you need the answer afterwards.