By the use of this method, the curve of retention, or curve of forgetting, as it is also called, has been determined. It is a curve that first goes down steeply, and then more and more gradually, till it approximates to zero; which means that the loss of what has been learned proceeds rapidly at first and then more and more slowly. The curve of forgetting can be determined by other methods besides the saving method--by the recall method or by the recognition method; and data obtained by these methods are given in the adjoining tables. It will be seen that the different methods agree in showing a curve that falls off more rapidly at first than later. More is lost in the first hour than in the second hour, and more in the first week than in the second week. Few of the experiments have been continued long enough to bring the curve actually to the zero line, but it has come very close to that line in tests conducted after an interval of two to four months. PER CENT. OF WORDS RECOGNIZED AT DIFFERENT INTERVALS AFTER BEING SEEN (From Strong) Interval between Per cent. recognized with exposure and test certainty and correctness 15 secs. 84 5 min. 73 15 min. 62 30 min. 58 1 hour 56 2 hours 50 4 hours 47 8 hours 40 12 hours 38 1 day 29 2 days 24 4 days 19 7 days 10 The subject read a list of 20 disconnected words once through, giving careful attention to each word. Immediately at the close of the reading he performed an example in mental arithmetic, to prevent his reviewing the list of words mentally. After an interval, he was shown these {352} twenty words mixed with twenty others, and had to pick out those he surely recognized as having been shown before. Many lists were used, for testing after the different intervals. Five adult subjects took part in the experiment, and in all 15 lists were used with each interval; the per cents. given in the table are the averages for the 15 lists. THE PER CENT. OF ERROR IN RECALLING DETAILS OF A PICTURE AFTER DIFFERENT INTERVALS OF TIME (From Dallenbach) Time of test Per cent, of error Per cent of error in spontaneous in answering recall questions regarding the picture Immediately after exposure 10 14 After 5 days 14 18 After 15 days 18 20 After 46 days 22 22