The UnforgettableWords.com Learning Routine

Rapid and steady increase in your vocabulary is possible with UnforgettableWords.com primarily because of the power of graduated interval recall coupled with an acclerated learning algorithm. Exercises show the word used in context multiple times which helps teach proper usage.

How a word is learned using UnforgettableWords.com

A word is learned using perhaps nine to fifteen vocabulary exercises that are intelligently spaced in time. To illustrate how this works, a typical learning of a word using ten exercises follows:

1. On the first exposure to the word, you see an excerpt from a classic book with the vocabulary word underlined. You select the correct definition of the word from a pair of choices using the paragraph context to help you choose the correct one. On completion of this first simple exercise, you score how well you knew the word prior to the exercise by clicking on a number from 1 to 10. The word was totally unfamiliar to you so you score it a 1. The computer program schedules the word for repetition the next day.
2. On the second day, you complete a second exercise seeing the word in a different context. This time you are shown an excerpt with a single word missing and replaced with a blank. The definition of the word is also supplied. You recognize the definition and, after checking that it makes since in context, select the correct missing word from a choice of four words. This exercise was easy, but you score the word a five on completion as you could recall the word's meaning from the day before but still don't fully understand the proper usage of the word. The computer schedules the word for repetition two days later.
3. On day 4, you see the word for the third time. This time the exercise is more difficult showing just an excerpt from a book with a blank replacing a missing word. You must select the correct missing word from a choice of four by examining the context. You then must select the correct definition of the word from a pair of choices. You score it a 7 on completion. Scores of 7, 8, or 9 are "passing" scores. With a passing score, the computer's goal changes from learning the meaning and usage of the word to efficiently burning the word into your long term memory using graduated interval recall. The computer sets a date for repetition four days ahead. This is the longest time you can wait and still have a 90% chance of remembering the word. The computer knows this because it has carefully studied your performance on prior vocabulary words and knows how long you can remember it with a 90% chance of scoring it "passing" on the next repetition.
4. The fourth repetition of the word occurs on day 6. The exposure to the word in different contexts four times has improved your understanding of the words meaning and usage. You score it an 8 after completing the exercise. The computer schedules the word for repetition 9 days later which it knows gives you a 90% chance of remembering the word. Note that the repetition interval increased from 4 days to 9. Successful recall of the word 4 days later has lengthened the time you are able to recall the word.
5. On day 15, you recall the word well and again score it an 8. The computer schedules the next repetition for 20 days later based on it's understanding of your memory. The repetition interval has increased from 9 days to 20 as successfully recalling the word after 9 days has strengthened your memory of the word to permit recall after a longer term.
6. On day 38 you score the word an 8 again. Note that you were scheduled to do the word on day 35 (day 15 + 20 days) but you took a few days off from your exercises. The computer gave you the word again on the next opportunity. Since you still remembered the word, the computer schedules the word for repetition 33 days later based on its understanding of your memory.
7. On day 71, you remember the word but not quite as strongly as you would like. You score it a 7. The computer realizes you're having some difficulty recalling this word so it schedules the next repetition for just 40 days later rather than the 66 days it would have scheduled if you had scored an 8.
8. On day 101, you score an 8 and the computer schedules the word for repetition 85 days later.
9. On day 186, you score an 8 and the computer schedules the word for repetition 170 days later. Before the 10th repetition, you see the word while reading twice and each time recognize it as one of your vocabulary words. This further strengthens your memory of this word. The computer will continue to repeat this word at increasing intervals but the truth is that repetition by the computer is no longer necessary. This word is yours and the haphazard exposure to the word occasionally during reading is sufficient reminder that you'll never forget it.
10. One year after you started learning this word the computer repeats it again. You wonder why this very familiar word was ever in your vocabulary list. You are totally confident that you'll never forget this word and score it a 10. With the score of 10 the computer dismisses it from your active list and doesn't repeat it ever again.

How does the computer know when to schedule the next repetition?

The first time you see a word the computer sets the next repetition length D1 (Days 1) to one, two, or three days depending on how you score the word (low scores will repeat in 1 day, higher scores in 3 days). On all future repetitions, the computer will increase the number of days Dn between successive exercises by a factor called the repetition ratio denoted Rn.

The repetition factor, Rn, is typically a number between 1.1 and 4 depending on the difficulty of the word. The computer determines difficulty by how you have scored the word (the details are explained later below). A typical value of Rn is about 2. The spacing between repetitions (in days) then might go like this:

D1=2, D2=4, D2=8, D3=16, D4=32, D5=64, D6=128, D7=256 ....

If a repetition ratio of 3 is used instead of 2, the days would be spaced as follows:

D1=2, D2=6, D2=18, D3=54, D4=162, D5=486 ....

You can see that using a larger repetition ratio would decrease the frequency of repetition and thereby allows you to spend your time learning more words. Unfortunately it also increases the percentage of words that you forget. UnforgettableWords.com selects the repetition ratio each time such that there is a 90% chance that you will score it "passing" the next time (the 90% is by default; you can change this percentage on your account page by changing the "remembering factor"). The chance that you will remember it the next time is calculated using the following formula

Here,

C represents the fraction of the time the word will be remembered correctly (scored higher than 6) on the next repetition.

S is the score the user gave on the most recent repetition.

Sp is the score the user gave on the prior repetition.

R is the repetition ratio.

T represents the trouble the user is having with the word. It is the fraction of times the user has successfully remembered the word on previous repetitions ( a low value of T means the user has had a lot of trouble).

a,b,c,d, and e are parameters that the computer "learns". On a weekly basis, the computer looks at your scoring history. This history includes the values of S, Sp, R, and T for the many word repetitions you have completed along with whether each of these repetitions resulted in successful recall of the word. The computer program then selects the values of a,b,c,d, and e such that the C funtion above is most accurate in predicting what fraction of words were successfully recalled. You can see your personal values of a,b,c,d and e on your account page. As a new user, you will start with default values of a, b, c, d, and e which are typical of UnforgettableWords.com users. After a month or so, the values will slowly start to change to reflect your personal memory. After several months the values of a, b, c, d, and e will solely reflect the computers analysis of your personal memory and scoring criteria.

With the values of a,b,c,d, and e determined, the computer has a formula that predicts the chance that you will successfully recall the word on the next repetion. The chance depends on the two most recent scores, how much trouble you've had with the word previously, and the repetition ratio R. The computer will then select R such that C is 0.90 meaning you will remember 90% of the time. Knowing the appropriate value of R and the number of days between the prior repetition, it then calculates the new date to repeat the word and schedules the repetition.

With this algorithm, the computer is effectively adjusting the repetition ratio depending on the difficulty of the word. This is taken into account by the values of T, S, and Sp. The parameters b and c are generally positive. That is higher scores result in an increased chance of a passing score on the next repetition. The paramater e is also generally positive. That is, a higher fraction of successful recall, T, of a word means it is more likely to be recalled on the next repetition. Finally, the parameter d is generally negative. That is, a larger repetition ratio, R, results in a lower chance of successful recall on the next repetition.