Any attempt to show why the mind acts in this way, any explanation of the way in which the different kinds of association are made possible, would bring us into physiological psychology, would involve a study of the brain and the nervous system. For our purposes it is sufficient to keep in mind that such associations do take place. Without them no idea can occur. Without them thought is impossible.

The bearing of all this on con­cen­tration has yet to be made plain. We must remember that every idea has more than one associate; in fact that each idea generally has a cluster of possible associates. Instead of suggesting the minuet, the one-step may have made the fox trot or the three-step occur to the young lady. It may have made her think of a young man with whom she danced it, or the trouble she had in learning it. Each of these sug­ges­tions, in turn, would also have potential connections with a cluster of ideas. When we are thinking at random—when we are day dreaming, as in the example given—the strongest association, or the first to be aroused, is the one we dwell upon. But when we are thinking with a purpose, in a word, when we are reasoning, we reject all associations which have no bearing on our purpose, and select only those which serve it.

Concentration does not, as popularly supposed, mean keeping the mind fastened on one object or idea or in one place. It consists in having a problem or purpose constantly before one. It means keeping our thought moving toward one desired end.

Concentration is often regarded as intense or focused attention. But the fact is that all attention is focused attention. Psychologists are fairly well agreed that we can attend to only one thing at a time. Mind wandering, and so-called distributed attention, is really attention directed first to one thing, then to another, then to another; or first to one thing, then to another, and then back again to the original object, resting but a few moments on each idea.

Concentration may best be defined as prolonged or sustained attention. It means keeping the mind on one subject or problem for a relatively long period, or at least continually reverting to some problem whenever one’s thoughts momentarily leave it.

Having decided just what we mean by con­cen­tration, our next step is to inquire whether con­cen­tration is worth while. The reader may smile at this question or he may be shocked, according to his temperament. But if most men were so convinced that con­cen­tration is such an unquestionable virtue, they would practice it a little more. At least they would make greater efforts to practice it than they do at present.

The truth is that con­cen­tration, per se, is of little value. The value of con­cen­tra­tion depends almost entirely on the subject con­cen­trated on. Almost any one will agree that even were a man to allow his mind to dwell now on one important problem and now on another, without stopping a very appreciable time at any, he might nevertheless be improving his time far more than a man who con­cen­trat­ed con­tinually on some in­sig­nif­i­cant and in­con­se­quen­tial question.

But of course this is not really an argument against con­cen­tration. It has no application when you con­cen­trate on the proper subject. For if you start to con­cen­trate on some question which you have decided is really important, you should keep at it, allowing no deviation. It may be that during the course of your thought associations will be aroused which will suggest or bear upon important problems, problems more important perhaps than the one you originally started to con­cen­trate on. But if you immediately abandoned every problem you started to think of, whenever you came across one which you imagined was just as important, you would probably never really solve any big question.

Our attention is guided by interest. If a man merely allows his thoughts to flow at random, thinking only of those things which spontaneously arouse his interest, he may or may not attend to things worth thinking about. All will depend upon the path in which his natural interests run. But the point is that if the subject he thinks about is valuable, it will be so only by accident; whether or not his thinking is useful will depend upon mere chance. If however he consciously chooses a subject—chooses it because he believes it to be important—then his thinking will be worth while.

But there is another reason why con­cen­tration is necessary. Suppose a man started to put up a barbed wire fence, got as far as driving in all the posts, then lost interest in the fences and decided to grow potatoes in his field, plowed up the ground, lost interest in the field and neglected to plant the seeds; decided to paint his house, got the porch done, lost interest . . . That man might work as hard as any other man, but he would never get anything done. So with the mind wanderer and the con­cen­trator. The mind wanderer thinks of a problem, loses interest, and abandons it. The con­cen­trator sticks to it until it is solved.