The pedagogical experiment has shown clearly enough that the subjective feeling of easier or quicker learning may be entirely unreliable and misleading.  If the task is to learn a page by heart, we may proceed after many different methods.  We may learn very small fractions of the text, repeating only a few words, or we may read whole paragraphs every time; we may repeat the whole material again and again, or we may put in long periods of rest after a few repetitions; we may frequently recite it from memory and have some one to prompt us; we may give our attention especially to the meaning of the words, or merely to the sounds, or we may introduce any number of similar variations.  Now the careful experiment shows that of two such methods one which appears to us the better and more appropriate in learning, perhaps even as the easier and more comfortable, may prove itself the less efficient one in the practical result.  The psychology of learning, which won its success by introducing meaningless syllables as experimental material, has slowly determined the most reliable methods for impressing knowledge on memory.  Where such results have once been secured, it would surely be a grave mistake simply to stick to the methods of so-called common sense and to leave it to the caprice of the individual teacher to decide what method of learning he will suggest to his pupils.  The best method is always the only one which should be considered.  The psychology of economic work must aim toward similar goals.  We must secure a definite knowledge as to the methods by which a group of movements can best be learned.  We must understand what value is to be attached to the repetitions and to the pauses, to the imitations and to the special combinations of movements, to the exercise in parts of the movements, to the rhythm of the work, and to many similar influences which may shape the learning process.

The simplest aspect, that of the mere repetition of the movement, has frequently been examined by psychophysicists.  The real founder of experimental psychology, Fechner, showed the way; he performed fatiguing experiments with lifted dumb-bells.  Then came the time in which the laboratories began to make a record of the muscular activities with the help of the ergograph, an instrument with which the movements of the arm and the fingers can easily be registered on the smoked surface of a revolving drum.  The subtlest variations of the activity, the increase and decrease of the psychomotor impulse, the mental fatigue, can be traced exactly in such graphic records.  This psychomotor side of the process, and not the mere muscle activity as such, is indeed the essential factor which should interest us.  The results of exercise are a training of the central apparatus of the brain and not of the muscular periphery.  The further development of those experiments soon led to complex questions, which referred not only to the mere change in the motor efficiency, but to the learning of particular groups