The Spacing Effect

In the 1880s, the German psychologist Hermann Ebbinghaus carried out a series of memory experiments on a single subject: himself. He memorized long lists of meaningless syllables, such as “DAX” and “BOK,” and then tested how many he could remember after different periods of time. His results showed that forgetting happens quickly at first and then slows down, a pattern now known as the forgetting curve.

Ebbinghaus also noticed something else. Lists that he studied in several shorter sessions spread over a few days were remembered better than lists studied the same number of times in a single session. This finding, called the spacing effect, has since been confirmed in hundreds of studies, with materials ranging from foreign vocabulary to medical procedures. [A] One explanation is that each time we return to information after a delay, we have to work a little harder to recall it. [B] This effort appears to strengthen the memory.

[C] Despite the strength of the evidence, many students still rely on cramming — studying intensively the night before an exam. [D] Cramming can work for a test the next morning, which may be why it remains popular. However, information learned this way tends to be forgotten soon afterward. For students who need to build on what they have learned in later courses, spacing out study sessions is a far more efficient strategy.