Yet commonsense can never be sufficient to find the right motor will impulses. The ideal distribution of pauses is extremely different from merely stopping the work when a state of overfatigue has been reached. Even general scientific rules could not be the last word. Subtle psychological tests would have to be devised by which the plan for alternation between work and rest could be carefully adjusted to the individual needs of every rural worker. The mere sensation of fatigue may be entirely misleading. It must be brought into definite relations to temperature, moistness, character of the work, training, and other factors. On the other hand, the absence of fatigue feeling would be in itself no indication that the limit of safety has not been passed, and yet the work itself must suffer when objective overfatigue of the system has begun. At the right moment a short interruption may secure again the complete conditions for successful work. If that moment has passed, an exhaustion may result which can no longer be repaired by a short rest. Any wrong method of performing these simple activities, that is, any method which is not based on exact scientific analysis, wastes the energies of the workingman, and by that the economic means of the farm owner, and indirectly the economic resources of the whole nation. In the Harvard Psychological Laboratory we are at present engaged in the investigation of such an apparently trivial function as sewing by hand. The finger which guides the needle is attached to a system of levers which write an exact graphic record of every stitch on a revolving drum. And the deeper we enter into this study the more we discover that such a movement, of which every seamstress and every girl who makes her clothes feels that she knows everything, contains an abundance of important features of which we do not as yet know anything. With the same scientific exactitude the laboratory must investigate the milking, or the making of butter, the feeding of the cattle and the picking of the fruit, the use of the scythe and the axe, the pruning and the husking. The mere fact that every one, even with the least skill, is able to carry out such movements with some result, does not in the least guarantee that any one carries them out to-day with the best result possible.