916 The American Naturalist. [October, 
What are the best means to adopt for preserving memory-images? 
What should be done in order to strengthen the memory, etc., etc. ? 
On all these points there have accumulated within the last ten years a 
countless number of documents; no synthesis of these data has yet been 
made, and I know of no general work in which the author has at- 
tempted to compare the results of these special studies and to draw 
forth their underlying principles; I except, of course, works on the 
mental pathology of the memory (Ribot, Sollier, etc.), which we are 
not concerned with here; I am only speaking of normal memory, 
studied with exactness by means of laboratory experimentation. 
The analysis of these experiments leads us to one conclusion regard- 
ing the nature of forgetfulness. It is of two kinds, and is due to two 
principal causes: (1) Forgetfulness through lack of retention ; the im- 
pression is not stamped in and does not leave a trace, this is the first 
kind; (2) Forgetfulness through lack of reproduction; the impression 
has been stamped in, but cannot be brought out or reproduced at will, 
e. g.,100 words being read to a person, how many does he forget? 
The answer varies according to the way in which the term forgetful- 
ness is interpreted. If we ask the subject to repeat the words, he will 
perhaps not be able to give more than 20, hence he has forgotten 80— 
forgotten them, in the sense that he cannot repeat them. This number 
can, therefore, be placed to the credit of forgetfulness through lack of 
reproduction. Now if we take these 80 words which the subject can- 
not repeat and mixing them up with one or two hundred new words, 
ask him to distinguish the old from the new words, we will see that he 
makes a very small number of errors ; I suppose that on the average 60 
words will be recognized out of 80, so that in the end there are scarcely 
20 words in 100 (and, perhaps, even fewer) that are completely for- 
gotten; the others were retained, inasmuch as they were recognized. 
The amount of forgetfulness through lack of retention is always small. 
The position of the forgotten elements in a series of memories ap- 
pears to be quite regular; the first elements in the series are almost 
always better retained than the rest, no doubt because they strike the 
attention when it is fresh; the same is true of the last elements, no 
doubt because they are the ones acquired most recently; most of the 
forgotten elements, then, belong to the centre of the series. The in- 
fluence of novelty, repetition and other factors on forgetfulness have 
been studied (Calkins), as well as the influence of the time elapsed (in 
numerous investigations), the organ stimulated, the attention, distrac- 
tion, etc. These investigations, many of them minute, have furnished 
us with matters of detail, rather than general ideas ALFRED BINET. 
