What is spaced repetition ? The science behind it

If you are preparing to take an exam, you have a few choices; revise properly, cram as much as you can the night before, or go to the test completely unprepared. Of course, unless you are a total genius, going into an exam totally unprepared is a very risky strategy. Cramming can work for some people, but the knowledge won’t stick. Within a week, the chances are that you will only be able to remember about 10% of the materials which you learned for the test – which is not great if you have an end of year exam on the topic as well. But if you take the time to revise properly, you can commit most of the knowledge to memory, and still be able to recall those important facts and figures years later. Using spaced repetition technique can be one of the best and most rewarding ways to memorise important learning material. In fact, in one memory study, students who used spaced repetition learning techniques were found to have outperformed other students in over 95% of cases (Cepeda et al, 2008).

Repetition learning strategies have been created by memory experts, who have studied the workings of the human brain and discovered that memorisation is easiest if the material is reviewed over and over again. Rather than reviewing materials at regular intervals, spaced repetition learning techniques gradually increase the space of time between each review of the learning material, in order to improve the chances of memorising the information. In other words, if you look at something 5 times in 2 days will help you remember the material for a few weeks, but looking at something 5 times over 2 months can help you to commit that information to memory for the rest of your life.

To understand the reasoning behind this, we must consider a principle which has become known as the “forgetting curve”. If no attempt is made to remember a fact, the memory of that fact will gradually decline over time and will eventually be forgotten, which can be portrayed on an exponential curve. Topping-up your memory by reviewing the material is a good way to refresh your memory and slow the rate of memory decay.

Experiments have shown that it is best to “top-up” a memory as the recall rate declines on the forgetting curve. After this first review, the rate of decline should be slower than after the very first time which you learned the information, and therefore it will take slightly longer for the memory recall rate to decline to a point where it is worth topping up. After the memory is topped up for a second time, the rate of decline should be even slower, and therefore the space between the first review and the second review should be longer than the length of time between the initial memorisation and the first review. As the rate of memory recall will decline even more slowly after the second review, the length of time between the second review and the third review will be even longer, and so on, until there is an insignificant decline in memory recall.


Spaced repetition apps are designed to offer you certain materials to review at the optimum time, so that you can gradually improve your memory recall. Interactive software can use the scientific basis given above to work out when you need to review information. Materials which you are struggling to commit to memory will be offered for review more often, and material which you are successfully recalling will be shown to you less frequently. As well as being effective, this technique can be fun, as flashcards have been designed to maximise your learning potential.


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