If you will examine the learning curve closely, you will note that after the initial spurt, there is a slowing up. The curve at this point resembles a plateau and indicates cessation of progress if not retrogression. This period of no progress is regarded as a characteristic of the learning curve and is a time of great discouragement to the conscientious student, so distressing that we may designate it "the plateau of despond." Most people describe it as a time when they feel unable to learn more about a subject; the mind seems to be sated; new ideas cannot be assimilated, and old ones seem to be forgotten. The plateau may extend for a long or a short time, depending upon the nature of the subject-matter and the length of time over which the learning extends. In the case of professional training, it may extend over a year or more. In the case of growing children in school, it sometimes happens that an entire year elapses during which the learning of an apparently bright student is retarded. In a course of study in high school or college, it may come on about the third week and extend a month or more. Something akin to the plateau may come in the course of a day, when we realize that our efficiency is greatly diminished and we seem, for an hour or more, to make no progress. Inasmuch as the plateau is such a common occurrence in human activity, we should analyze it and see what factors operate to influence it. It is interesting to note that the plateau generally occurs just before an abrupt rise in efficiency. This is significant, for it may mean that the plateau is necessary in learning, especially just before reaching the really advanced stages of proficiency. Accordingly, when you are experiencing a plateau in the mastery of some accomplishment, you may perhaps derive some comfort from the prospect of an approaching rise in efficiency. On the theory that it is a necessary part of learning, it has been regarded as a resting place. We are so constituted by nature that we cannot run on indefinitely; nature sometimes must call a halt. Consequently, the plateau may be a warning that we cannot learn more for the present and that the proper remedy is to refrain for a little while from further efforts in that line. We have possible justification for this interpretation when we reflect that a vacation does us much good, and though we begin it feeling stale, we end it feeling much fresher and more efficient. But to stop work temporarily is not the only way to meet a plateau, and fatigue or ennui is probably not the sole or most compelling explanation. It may be that we should not regard the objective results as the true measure of learning; perhaps learning is going on even though the results are not apparent. We discovered something in the nature of unconscious learning in our discussion of memory, and it may be that a period of little objective progress marks a period of active unconscious learning.