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Why we forget

Our brain does not have an unlimited capacity to store and recall information. In order to function every day, make decisions and draw conclusions, we need to retain the information which is important to us and discard that which is unimportant. Think of a memory stick that has reached its maximum storage capacity. You delete the least important files and documents in order to make space for new data.

Forgetting is the essential biological process that allows us to sort incoming facts and data into important and unimportant. If we didn't forget, we would be overloaded with useless information and simply unable to think.

The problem is that, unlike the data stored on a memory stick, the information in our memory banks cannot easily be retained or discarded at will. We cannot simply tell ourselves "I will remember this word." Our brain must decide that a particular piece of information is important to us before it is committed to long-term memory.

The figure below presents a typical memory retention curve, showing the percentage of recently learned information that can be remembered after several days have elapsed:

Spaced repetition

Hermann Ebbinghaus (1850-1909)

The way the human brain retains information has been the subject of serious scientific study since the late nineteenth century. One method of enhancing retention takes advantage of the way the brain consolidates information from short-term to long-term memory,where it can be recalled almost indefinitely. This is the idea of 'spaced repetition', first developed by the German psychologist Hermann Ebbinghaus (1850-1909). Through extensive experimentation with lists of "nonsense words", Ebbinghaus discovered that the rate at which we start to forget a recently learned or reviewed item of knowledge follows a predictable pattern. Significantly, the process of forgetting slows down after each repetition or review, and with time increasingly less frequent reviews are needed in order to remember an item of any level of difficulty.

Since Ebbinghaus' time, sophisticated algorithms (sets of mathematical equations) have been developed to calculate the optimum intervals between each repetition, minimizing the number of repetitions needed and maximizing the period of retention. Early experiments used simple paper question-and-answer flashcards. The learner was first shown the question part of the flashcard and, depending on the response, the flashcard was scheduled for future repetition. Unfortunately, due to the extremely time-consuming process of creating flashcards and manually scheduling their review, the method was completely impractical for everyday use. However, since the advent of computing, spaced repetition has become a practical and highly efficient speed-learning method.

The Expemo method

The Expemo method consists of reviewing electronic flashcards. Each flashcard is scheduled for future review according to state-of-the-art algorithms. Difficult flashcards are reviewed more often than easier flashcards, with decreasing frequency over time. With each optimized repetition, the percentage of learned material that can be remembered increases. Best results can be achieved with short, regular review sessions (usually no more than 20 minutes per day for around 1000 flashcards).

With the Expemo method, the memorization process is further enhanced in the design of flashcards, which incorporate audio-visual elements to improve the learning experience and create stronger memories.