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What Is the Optimally Efficient Gap Between Study Sessions?

Spacing study sessions governs long-term memory.

We have all been told by teachers that learning occurs best when we spread it out over time, rather than trying to cram everything into our memory banks at one time. But what is the optimal spacing? There is no general consensus.

However we do know that immediately after a learning experience the memory of the event is extremely volatile and easily lost. It's like looking up a number in the phone book: if you think about something else at the same time you may have to look the number up again before you can dial it. School settings commonly create this problem. One learning object may be immediately followed by another, and the succession of such new information tends to erase the memory of the preceding ones.

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Source: Microsoft clip art

Memory researchers have known for a long time that repeated retrieval enhances long-term retention. This happens because each time we retrieve a memory, it has to be reconsolidated and each such reconsolidation strengthens the memory. Though optimal spacing intervals have not been identified, research confirms the importance of spaced retrieval. No doubt, the nature of the information, the effectiveness of initial encoding, competing experiences, and individual variability affect the optimal interval for spaced learning.

One study revealed that repeated retrieval of learned information (100 Swahili–English word pairs) with long intervals produced a 200% improvement in long-term retention relative to repeated retrieval with no spacing between tests. Investigators compared different-length intervals of 15, 30, or 90 minute spacing that expanded (for example, 15-30-45 min), stayed the same (30-30-30 min) or contracted (45-30-15 min) revealed that no one relative spacing interval pattern was superior to any other [1].

Another study [2] has revealed that the optimally efficient gap between study sessions depends on when the information will be tested in the future. A very comprehensive study of this matter in 1,350 individuals involved teaching them a set of facts and then testing them for long-term retention after 3.5 months. A final test was given at a further delay of up to one year. At any test delay, increasing the inter-study gap between the first learning and a study of that material at first increased and then gradually reduced final test performance. Expressed as a ratio, the optimal gap equaled 10-20% of the test delay. That is, for example, a one-day gap was best for a test to be given seven days later, while a 21-day gap was best for a test 70 days later. Few of any teachers or students know this, and their study times are rarely scheduled in any systematic way, typically being driven by test schedules for other subjects, convenience, or even the teacher's whim.

The bottom line: the optimal time to review a newly learned experience is just before you are about to forget it. Obviously, we usually don't know when this occurs, but in general the vast bulk of forgetting occurs within the first day after learning. As a rule of thumb, you can suspect that a few repetitions early on should be helpful in fully encoding the information and initiating a robust consolidation process. So, for example, after each class a student should quickly remind herself what was just learned—then that evening do another quick review. Before the next class on that subject, the student should review again. Teachers help this process by linking the next lesson to the preceding one.

Certain practices will reduce the amount of time needed for study and the degree of long-term memory formation. These include:

• Don't procrastinate. Do it now!

• Organize the information in ways that make sense (outlines, concept maps)

• Identify what needs to be memorized and what does not.

• Focus. Do not multi-task. No music, cell phones, TV or radio, or distractions of any kind.

• Association the new with things you already know.

• Associate words with mental images and link images to locations, or in story chains

• Think hard about the information, in different contexts

• Study small chunks of material, in short intervals. Then take a mental break.

• Say out loud what you are trying to remember.

• Practice soon after learning and frequently thereafter at spaced intervals.

• Explain what you are learning to somebody else.

Work with study groups after you have prepared.

• Self-test. Don't just "look over" the material. Truly engage with it.

• Never, never, ever CRAM!

1. Karpicke, J. d., and Bauernschmidt, a. 2011. Spaced retrieval: absolute spacing enhances learning regardless of relative spacing. J. Exp. Psychol. 37 (5) 1250-1257.

2. Cepeda, N. J. et al. 2008. Spacing effects in learning. A temporal ridgeline of optimal retention. 19 (11): 1095-1102

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