This problem has been followed up very recently in a valuable investigation at Columbia University,[23] in which various habits of typewriting and of card-sorting were acquired and studied in their mutual interference.  These very careful experiments also show that when two opposing associations are alternately practiced, they have an interference effect on each other, but that the interference grows less and less as the practice effect becomes greater.  The interference effect is gradually overcome and both opposing associations become automatic, so that either of them can be called up independently without the appearance of the other.  Many details of the research suggest that this whole group of interference problems deserves the most careful attention by those who would practically profit from increased industrial efficiency.

Finally, in the experimental study of the problem of technical learning, we cannot ignore the many side influences which may hasten or delay, improve or disturb, the acquisition of industrial skill.  In the Harvard laboratory, for instance, we are at present engaged in an investigation which deals with the influence of feelings on the rapidity with which new movement cooerdinations are mastered.[24] In order to have unlimited comparable material a very simple technical performance is required, namely, the distribution of the 52 playing-cards into 52 boxes.  Labels on the boxes indicate changing combinations for the distribution to be learned.  We examine, on the one side, the influence of feelings of comfort or of discomfort on the learning of the new habit, these feeling states being produced by external conditions, such as pleasant or unpleasant sounds, odors, and so on.  On the other side we trace the effects of those feelings which arise during the learning process itself, such as feelings of satisfaction with progress, or disappointment, or discomfort, or disgust or joy in the activity.

XIV

THE ADJUSTMENT OF TECHNICAL TO PSYCHICAL CONDITIONS

Teaching and learning represent only the preliminary problem.  The fundamental question remains, after all, how the work is to be done by those who have learned it in accordance with the customs of the economic surroundings and who are accordingly already educated and trained for it.  What can be done to eliminate everything which diminishes and decreases efficiency, and what remains to be done to reinforce it.  Such influences are evidently exerted by the external technical conditions, by variations of the activity itself, and by the play of the psychical motives and counter-motives.  It must seem as if only this last factor would belong in the realm of psychology, but the technical conditions, of which the machine itself is the most important part, and the bodily movements also have manifold relations to the psychical life.  Only as far as these relations prevail has the psychologist any reason to study the problem.