Intelligence, as has been frequently pointed out, while it does not depend upon the individual’s ability to read and write, is so generally accompanied by the definite and intimate knowledge of the symbols which we call letters, words, and figures, and of their meaning, that in the great majority of cases in which it is desired to apply the test of intelligence this can best be done, or at least most readily be done, by the use of these familiar symbols; in other words, by tests which involve only the acts of reading and writing. If intelligence may be defined as the intellectual power of adaptation to environment, a complete test of intelligence determines the individual’s ability to recognize the situation in which he finds himself, perceive his own relation to the situation, analyze it, and arrive at a conclusion as to what he should do next; then put that conclusion into effect by means of a concrete act. Thus one may learn a great deal about an individual’s mental capacity by observing his conduct when he misses a train. But since it is not practicable to apply this method of inquiry in every case, the next best thing is to ask the question, “What would you do if you missed your train?” To ask this question of a subject is next best to seeing him in such a situation. He must exercise his sense of reality upon it, size it up and plan his reaction. Since all life is made up of situations in which the individual places or finds himself and from which he must extricate himself, and since the broader the mental capacity, the more easily will the individual meet situations as they arise, the ideal mental test is one that presents a situation such as does or might occur in real life, and requires the subject to extricate himself, or at least to indicate his first and immediate impulse toward action should such a situation arise. Since the purpose of mental tests is primarily to determine intelligence rather than the possession of physical qualities, it is conceivable that, in many situations, properly devised questions may give a fairer view of the subject’s mental capacity than would observation of the same individual in action in a real situation. Thus a person of the highest intelligence and mental capacity might be deficient in physical courage, so that if we could observe him in action on unexpectedly meeting a highway robber armed with a revolver we might be able to deduce from his actions absolutely no criteria upon which to form a sound judgment as to his mental powers; the same subject, asked the question, “What would you do if held up by a footpad?” might exhibit in his answer unusual ability to perceive quickly and reason soundly to an intelligent conclusion—in other words, to demonstrate his possession of considerable mental capacity.