The third problem, which is given in the same way, states that there are _three_ smaller boxes, each of which contains _three_ tiny boxes. In the fourth problem there are _four_ smaller boxes, each containing _four_ tiny boxes. The problem must be given orally, and the solution must be found without the aid of pencil or paper. Only one half-minute is allowed for each problem. Note that each problem is stated twice. A correction is permitted, provided it is offered spontaneously and does not seem to be the result of guessing. Guessing can be checked up by asking the subject to explain the solution. SCORING. _Three of the four_ problems must be solved correctly within the half-minute allotted to each. REMARKS. Success depends, in the first place, upon ability to comprehend the statement of the problem and to hold its conditions in mind. Subjects much below the 12-year level of intelligence are often unable to do this. Granting that the problem has been comprehended, success seems to depend chiefly upon the facility with which the constructive imagination manipulates concrete visual imagery. In this respect it resembles the problem of reversing the hands of a clock. With some subjects, however, verbal imagery alone is operative. Tactual imagery would, of course, serve the purpose as well. This is as good a place as any to emphasize the fact that the introspective study of mental imagery has little to contribute to the measurement of intelligence. Intelligence tests are concerned with the total result of a thought process, rather than with the imagery supports of that process. Thought may be carried on almost equally well by various kinds of imagery. As Galton showed, a person can be taught to carry on arithmetical processes by the use of smell imagery. The kind of imagery employed is the product of slight, innate preferences complicated by the more or less accidental effects of habit. We may say that imagery is to thinking what scaffolding is to architecture. The important thing is the completed building rather than the nature of the scaffolding employed in erecting it. No one thinks of blaming the ill construction of a building upon the kind of scaffolding used, for if the architect and builder are competent satisfactory scaffolding will be found. Just as little are deficiencies or peculiarities of imagery the real cause of low-order intelligence. We cannot increase intelligence by formal drill in the use of supposedly important kinds of mental imagery, any more than we can transform a plain carpenter into a Michael Angelo by instructing him in the use of scaffolding materials such as were employed in the construction of St. Peter's Cathedral.