That this difficulty is a real one no one who has examined students will be disposed to deny. When we ask them to reproduce what the text-book or the professor's lectures have taught, we also ask them to express themselves accurately. Now the science of correct expression is a thing in which the average student has had no training. With his difficulty in remembering is connected his difficulty of expression; and with it all goes a certain embarrassment, due to responsibility, personal fear, and dread of disgrace. So the results finally obtained by this method are really very complex.
One of the curves, that given by the method of Selection (I), also shows memory to be interfered with by a certain influence. We saw in connection with the experiments reported above that, even in the most elementary arrangements of squares in the visual fields, an element of contrast comes in to interfere with our judgment of size. This we find confirmed in these experiments when the method of Selection is used. By this method we show a number of squares side by side, asking the individual to select the one he saw before. All the squares, being shown at once, come into contrast with one another on the background; and so his judgment of the size of the one he remembers is distorted. This, again, is a real influence in our mental lives, leading to actual illusion. An unscrupulous lawyer may gradually modify the story which his client or a witness tells by constantly adding to what is really remembered, other details so expertly contrasted with the facts, or so neatly interposed among them, that the witness gradually incorporates them in his memory and so testifies more nearly as the lawyer desires. In our daily lives another element of contrast is also very strong--that due to social opinion. We constantly modify our memories to agree more closely with the truths of social belief, paring down unconsciously the difference between our own and others' reports of things. If several witnesses of an event be allowed to compare notes from time to time, they will gradually come to tell more nearly the same story.
The other curve (II) in the figure, that secured by the method of Identification, seemed to the investigators to be the most accurate. It is not subject to the errors due to expression and to contrast, and it has the advantage of allowing the subject the right to recognise the square. It is shown to him again, with no information that it is the same, and he decides whether from his remembrance of the earlier one, it is the same or not. The only objection to this method is that it requires a great many experiments in order to get an average result. To be reliable, an average must be secured, seeing that, for one or two or a few trials, the student may guess right without remembering the original square at all. By taking a large number of persons, such as the three hundred students, this objection may be overcome. Comparing the averages, for example, of the results given by the men and women respectively, we found practically no difference between them.