“Only a few psychologists have been interested in the problem. Most of the psychologists, it is to be regretted, have even failed to see that there is a problem. They believe habit formation is implanted by kind fairies. For example, Thorndike speaks of pleasure stamping in the successful movement and displeasure stamping out the unsuccessful movements. Most of the psychologists talk, too, quite volubly about the formation of new pathways in the brain, as though there were a group of tiny servants of Vulcan there who run through the nervous system with hammer and chisel digging new trenches and deepening old ones. I am not sure that the problem when phrased in this way is a soluble one. I feel that there must come some simpler way of envisaging the whole process of habit formation or else it may remain insoluble. Since the advent of the conditioned reflex hypothesis in psychology with all of the simplifications (and I am often fearful that it may be an oversimplification!) I have had my own laryngeal processes [_i.e._ what others call “thoughts”] stimulated to work upon this problem from another angle.” I agree with Dr. Watson that the explanations of habit-formation which are usually given are very inadequate, and that few psychologists have realised either the importance or the difficulty of the problem. I agree also that a great many cases are covered by his formula of the conditioned reflex. He relates a case of a child who once touched a hot radiator, and afterward avoided it for two years. He adds: “If we should keep our old habit terminology, we should have in this example a habit formed by a single trial. There can be then in this case no ‘stamping in of the successful movement’ and ‘no stamping out of the unsuccessful movement.’” On the basis of such examples, he believes that the whole of habit-formation can be derived from the principle of the conditioned reflex, which he formulates as follows (p. 168): _Stimulus X will not now call out reaction R; stimulus Y will call out reaction R (unconditioned reflex); but when stimulus X is presented first and then Y (which does call out R) shortly thereafter, X will thereafter call out R. In other words, stimulus X becomes ever thereafter substituted for Y._ This law is so simple, so important, and so widely true that there is a danger lest its scope should be exaggerated, just as, in the eighteenth century, physicists tried to explain everything by means of gravitation. But when considered as covering all the ground, it seems to me to suffer from two opposite defects. In the first place, there are cases where no habit is set up, although by the law it should be. In the second place, there are habits which, so far as we can see at present, have a different genesis.