The measurement of intelligence

by Lewis M. Terman

Procedure. Place the five boxes on the table in an irregular group before the child and say: “See the boxes. They all look alike, don’t they? But they are not alike. Some of them are heavy, some are not quite so heavy, and some are still lighter. No two weigh the same. Now, I want you to find the heaviest one and place it here. Then find the one that is just a little lighter and put it here. Then put the next lighter one here, and the next lighter one here, and the lightest of all at this end (pointing each time at the appropriate spot). Do you understand?” Whatever the child answers, in order to make sure that he does understand, we repeat the instructions thus: “Remember now, that no two weights are the same. Find the heaviest one and put it here, the next heaviest here, and lighter, lighter, until you have the very lightest here. Ready; go ahead.”

It is best to follow very closely the formula here given, otherwise there is danger of stating the directions so abstractly that the subject could not comprehend them. A formula like “I want you to arrange the blocks in a gradually decreasing series according to weight” would be Greek to most children of 10 years.

If the subject still seems at a loss to know what to do, the instructions may be again repeated. But no further help of any kind may be given. Do not tell the subject to take the blocks one at a time in the hand and try them, and do not illustrate by hefting the blocks yourself. It is a part of the test to let the subject find his own method.

Give three trials, shuffling the boxes after each. Do not repeat the instructions before the second and third trials unless the subject has used an absurd procedure in the previous trial.

Scoring. The test is passed if the blocks are arranged in the correct order twice out of three trials. Always record the order of arrangement and note the number and extent of displacement. Obviously an arrangement like 12–6–15–3–9 is very much more serious than one like 15–12–6–9–3, but we require that two trials be absolutely without error.

Scoring is facilitated if the blocks are marked on the bottom so that they may be easily identified. It is then necessary to exercise some care to see that the subject does not examine the bottom of the blocks for a clue as to the correct order.

Remarks. Binet originally located this test in year IX, but in his 1911 revision changed it to year VIII. Other revisions have retained it in year IX. The correct location depends upon the weights used and upon the procedure and scoring. Kuhlmann uses weights of 3, 9, 18, 27, 36, and 45 grams, and this probably makes the test easier. Bobertag tried two sets of boxes, one set being of larger dimensions than the other. The larger gave decidedly the more errors. If we require only one success in three trials the test could be located a year or two lower in the scale, while three successes as a standard would require that it be moved upward possibly as much as two years.

Much depends also on whether the child is left to find his own method, and on this there has been much difference of procedure. Kuhlmann, Bobertag, and Wallin illustrate the correct method of making the comparison by first hefting and arranging the weights while the subject looks on. We prefer to keep the test in its original form, and with the procedure and scoring we have used it is well located in year IX.

Wallin carries his assistance still further by saying, after the first block has been placed, “Now, find the heaviest of the four,” and after the second has been placed, “Now, find the heaviest of the three,” etc. Finally, when the arrangement has been made, he tells the subject to try them again to make sure the order is correct, allowing the subject to make whatever changes he thinks necessary. This procedure robs the test of its most valuable features. The experiment was not devised primarily as a test of sensory discrimination, for it has long been recognized that individuals who have developed as far as the 9- or 10-year level of intelligence are ordinarily but little below normal in sensory capacity.

Psychologically, the test resembles that of comparing weights in [V, 1]. Success depends, in the first place, upon the correct comprehension of the task and the setting of a goal to be attained; secondly, upon the choice of a suitable method for realizing the goal; and finally, upon the ability to keep the end clearly in consciousness until all the steps necessary for its attainment have been gone through. Elementary as are the processes involved, they represent the prototype of all purposeful behavior. The statesman, the lawyer, the teacher, the physician, the carpenter, all in their own way and with their own materials, are continually engaged in setting goals, choosing means, and inhibiting the multitudinous appeals of irrelevant and distracting ideas.