The two great laws of habit formation are the laws of exercise and effect.  These laws apply in all cases of habit formation, whether they be the purposeless habits of children or the purposive habits of maturity.  The law of exercise says that the oftener and the more emphatically a certain response is connected with a certain situation, the more likely is it to be made to that situation.  The two factors of repetition and intensity are involved.  It is a common observance that the oftener one does a thing, other things being equal, the better he does it, whether it be good or bad.  Drill is the usual method adopted by all classes of people for habit formation.  It is because of the recognition of the value of repetition that the old maxim of “Practice makes Perfect” has been so blindly adhered to.  Practice may make perfect, but it also may make imperfect.  All that practice can do is to make more sure and automatic the activity, whatever it is.  It cannot alone make for improvement.  A child becomes more and more proficient in bad writing or posture, in incorrect work in arithmetic and spelling, with practice just as truly as under other conditions he improves in the same activities.  Evidence from school experiments, which shows that as many as 40 per cent of the children examined did poorer work along such lines in a second test than in the first which had been given several months earlier, bears witness to the inability of mere repetition to get “perfect” results.  To get such results the repetition must be only of the improvements.  There must be a constant variation towards the ideal, and a selection of just those variations for practice, if perfect as well as invariable results are to be obtained.

The amount of repetition necessary in the formation of any given habit is not known.  It will, of course, vary with the habit and with the individual, but experimental psychology will some day have something to offer along this line.  We could make a great saving if we knew, even approximately, the amount of practice necessary under the best conditions to form some of the more simple and elementary habits, such as learning the facts of multiplication.

One other fact in connection with repetition should be noted, namely, that the exercise given any connection by the learner, freely, of his own initiative counts more than that given under purposive learning.  This method of learning is valuable in that it is incidental and often saves energy and possible imitation on the part of the child, but it has certain drawbacks.  Habits formed this way are ingrained to such an extent that they are very difficult to modify.  They were not consciously attended to when they were formed, and hence it is difficult later to raise them to the focal point.  Hence it is best whenever habits are partial and will need to be modified later, or when the habits must later be rationalized, or when bad habits must be broken, to have the process focalized in attention.  The methods of gaining attention have already been discussed.