In the experiments, the students were asked to predict how much they would remember a week after using one of the methods to learn the material. Those who took the test after reading the passage predicted they would remember less a week later than the other students predicted — but the results were just the opposite.
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Why retrieval testing helps is still unknown. Perhaps it is because by remembering information we are organizing it and creating cues and connections that our brains later recognize.
“When you’re retrieving something out of a computer’s memory, you don’t change anything — it’s simple playback,” said Robert Bjork, a psychologist at the University of California, Los Angeles, who was not involved with the study.
But “when we use our memories by retrieving things, we change our access” to that information, Dr. Bjork said. “What we recall becomes more recallable in the future. In a sense you are practicing what you are going to need to do later.”
This fits my experience. I took my share of standardized tests in grade school (I remember taking the Iowa Test of Basic Skills in elementary school). The subjects were usually not that interesting, but I would recall the subjects and silly little facts from them years later. One 7th-grade test included a passage about beriberi—a disease caused by a vitamin deficiency linked to eating polished (white?) rice—that I still vaguely recall today.