Not only do the demands of economy require that the topic of study receive concentrated attention, but the results themselves are better when such is the case. Half an hour of concentrated work gives much better results than an hour of study with scattered attention. An hour spent when half an hour would do is thus not only wasteful of time, but is productive of poorer results and bad habits of study as well. Children need to be taught this from the beginning. Much time is wasted even by mature university students when they suppose themselves to be studying. Children can be taught to ignore distractions--to train themselves to keep their eyes on the book, despite the fact that the door is opened, or a seat mate is looking for a book. They should be encouraged to set themselves time limits in various subjects and adhere to them. It is economical to follow a regular schedule in study--either in the school or at home. Let each child make out his study schedule and keep to it. Teach children that the best work is done when they are calm and steady. That either excitement or worry is a hindrance. Therefore they should avoid doing their studying under those conditions, and should do all they can to remove such conditions. Training children to do their best and then not to worry would not only improve the health of many upper grammar grade and high school children, but would also improve their work. Study requires a certain critical attitude, a checking up of results against the problem set. In order to be efficient in study a child should know when he has reached the solution, when the means have been adapted to the end, when he has reached the goal. This checking up, of course, means habits of self-criticism and standards. Sometimes all that is necessary is for the child to be made conscious of this fact so that he can test himself, for instance, in memory work, or in solving a problem in mathematics. On the other hand, sometimes he will have to compare his work with definite standards, such as the Thorndike Handwriting Scale, or the Hillegas Composition Scale.[19] In other instances, he will have to search for standards. He will need to know what his classmates have accomplished, what other people think, what other text-books say, and so on. Gradually he must be made conscious that study is a controlled activity, and unless it reaches the goal, and the correct one, it is useless. He must be made to feel that the responsibility to see that such results are reached rests on him. These, then, are the general factors involved in all types of study, and therefore are fundamental to good habits of study: a clear purpose; vital interest of some kind; concentrated attention, and a critical attitude. There are further additional suggestions which are peculiar to the special type of study.