CHAPTER XI
INSTRUCTIONS FOR YEAR V
V, 1. Comparison of weights
Materials. It is necessary to have two weights, identical in shape, size, and appearance, weighing respectively 3 and 15 grams.[50] If manufactured weights are not at hand, it is easy to make satisfactory substitutes by taking stiff cardboard pill-boxes, about 1¼ inches in diameter, and filling them with cotton and shot to the desired weight. The shot must be embedded in the center of the cotton so as to prevent rattling. After the box has been loaded to the exact weight, the lid should be glued on firmly. If one does not have access to laboratory scales, it is always possible to secure the help of a druggist in the rather delicate task of weighing the boxes accurately. A set of pill-box weights will last through hundreds of tests, if handled carefully, but they will not stand rough usage. The manufactured blocks are more durable, and so more satisfactory in the long run. If the weights are not at hand, the alternative test may be substituted.
Procedure. Place the 3- and 15-gram weights on the table before the child some two or three inches apart. Say: “You see these blocks. They look just alike, but one of them is heavy and one is light. Try them and tell me which one is heavier.” If the child does not respond, repeat the instructions, saying this time, “Tell me which one is the heaviest.” (Many American children have heard only the superlative form of the adjective used in the comparison of two objects.)
Sometimes the child merely points to one of the boxes or picks up one at random and hands it to the examiner, thinking he is asked to guess which is heaviest. We then say: “No, that is not the way. You must take the boxes in your hands and try them, like this” (illustrating by lifting with one hand, first one box and then the other, a few inches from the table). Most children of 5 years are then able to make the comparison correctly. Very young subjects, however, or older ones who are retarded, sometimes adopt the rather questionable method of lifting both weights in the same hand at once. This is always an unfavorable sign, especially if one of the blocks is placed in the hand on top of the other block.
After the first trial, the weights are shuffled and again presented for comparison as before, this time with the positions reversed. The third trial follows with the blocks in the same position as in the first trial. Some children have a tendency to stereotyped behavior, which in this test shows itself by choosing always the block on a certain side. Hence the necessity of alternating the positions.[51] Reserve commendation until all three trials have been given.
Scoring. The test is passed if two of the three comparisons are correct. If there is reason to suspect that the successful responses were due to lucky guesses, the test should be entirely repeated.
Remarks. This test is decidedly more difficult than that of comparing lines ([IV, 1]). It is doubtful, however, if we can regard the difference as one due primarily to the relative difficulty of visual discrimination and muscular discrimination. In fact, the test with weights hardly taxes sensory discrimination at all when used with children of 5-year intelligence. Success depends, in the first place, on the ability to understand the instructions; and in the second place, on the power to hold the instructions in mind long enough to guide the process of making the comparison. The test presupposes, in elementary form, a power which is operative in all the higher independent processes of thought, the power to neglect the manifold distractions of irrelevant sensations and ideas and to drive direct toward a goal. Here the goal is furnished by the instruction, “Try them and see which is heavier.” This must be held firmly enough in mind to control the steps necessary for making the comparison. Ideas of piling the blocks on top of one another, throwing them, etc., must be inhibited. Sometimes the low-grade imbecile starts off in a very promising way, then apparently forgets the instructions (loses sight of the goal), and begins to play with the boxes in a random way. His mental processes are not consecutive, stable, or controlled. He is blown about at the mercy of every gust of momentary interest.
There is very general agreement in the assignment of this test to year V.