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 11/4 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. 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.