Somewhat different from the matter of the curve of forgetting is the question of the rate of forgetting, as [{353}] dependent on various conditions. The rate of forgetting depends, first, on the thoroughness of the learning, as we have just seen. It depends on the kind of material learned, being very much slower for meaningful than for nonsense material, though both have been learned equally well. Barely learned nonsense material is almost entirely gone by the end of four months, but stanzas of poetry, just barely learned, have shown a perceptible retention after twenty years.
Very fortunately, the principles of economy of memorizing hold good also for retention. Forgetting is slower when relationships and connections have been found in the material than when the learning has been by rote. Forgetting is slower after active recitation than when the more passive, receptive method of study has been employed. Forgetting is slower after spaced than after unspaced study, and slower after whole learning than after part learning.
An old saying has it that quick learning means quick forgetting, and that quick learners are quick forgetters. Experiment does not wholly bear this out. A lesson that is learned quickly because it is clearly understood is better retained than one which is imperfectly understood and therefore slowly learned; and a learner who learns quickly because he is on the alert for significant facts and connections retains better than a learner who is slow from lack of such alertness. The wider awake the learner, the quicker will be his learning and the slower his subsequent forgetting; so that one is often tempted to admonish a certain type of studious but easy-going person, "for goodness' sake not to dawdle over his lessons", with any idea that the more time he spends with them the longer he will remember them. More gas! High pressure gives the biggest results, provided only it is directed into high-level observation, and does not simply generate fear and worry and a rattle-brained frenzy of rote learning.
Recall
Having committed something to memory, how do we get it back when we want it? To judge from such simple cases as the animal's performance of a previously learned reaction, all that is necessary is a stimulus previously linked with the response. How, for example, shall we get the cat to turn the door-button, this being an act that the cat has previously learned? Why, we put the cat into the same cage, i.e., we supply the stimulus that has previously given the reaction, and trust to it to give the same reaction again. The learning process has attached this reaction to this stimulus. Now can we say the same regarding material committed to memory by the human subject? Is recall a species of learned reaction that needs only the linked stimulus to arouse it?
If you have learned and still retain a list of numbers or syllables, you can recite it on thinking of it, on hearing words that identify it in your mind, or on being given the first few items in the list as a start. The act of reciting the list became linked, during the learning, with the thought of the list, with words signifying this particular list, and with the first items of the list; therefore, these stimuli can now arouse the reaction of reciting the list. As you advance into the list, reciting it, the parts already recited act as stimuli to keep you going forward. In the same way, if you have memorized Hamlet's soliloquy, this title serves as the stimulus to make you recall the beginning of the speech and that in turn calls up the next part and so on; or, if you have analyzed the speech into an outline, the title calls up the outline and the outline acts as the stimulus to call up the several parts that were attached to the outline in the process of memorization. When one idea calls up another, the first acts as a stimulus and the second is a [{355}] response previously attached to this stimulus. In general, then, recall is a learned response to a stimulus.
There is an exceptional case, where recall seems to occur without any stimulus. This form of recall goes by the name of perseveration, and a good instance of it is the "running of a tune in the head", shortly after it has been heard. Another instance is the vivid flashing of scenes of the day before the "mind's eye" as one lies in bed before going to sleep. It appears as if the sights or sounds came up of themselves and without any stimulus. Possibly there is some vague stimulus which cannot itself be detected. Only a slight stimulus would be needed, because these recent and vivid experiences are so easily aroused.
Difficulties in recall.
Sometimes recall fails to materialize when we wish it and have good reason for expecting it. We know this person's name, as is proved by the fact that we later recall it, but at the moment we cannot bring it up. We know the answer to this examination question, but in the heat of the examination we give the wrong answer, though afterwards the right answer comes to mind. This seldom happens with thoroughly learned facts, but frequently with facts that are moderately well known. Some sort of inhibition or interference blocks recall.