This operation required good eyesight (in order to distinguish defects, which frequently were so minute as to be indistinguishable to all but the best of eyes); keen visual discrimination (the ability to determine, with a few glances, which shells were defective); quick reaction (ability to extract, as quickly as seen, the defective shell and toss it into the appropriate box); accuracy of movement (ability to pick out the right shell from a closely held handful); steadiness of attention (ability to prevent bad shells from slipping by or unduly lengthening the operation).
A set of eight tests was selected for the body of the experiment. The first was a simple eyesight test. The second was a card sorting test. The subject was given a pack of 49 cards, upon the face of each one of which from 7 to 12 letters were distributed promiscuously. Twenty of the cards contained the letter “O” and the rest did not. The subject was asked to sort these into two piles, those which had “O” on them and those which had not. The time required for this performance was taken and the number of errors recorded. The object of the test was to bring out the subject’s ability to pick out the essential element from a more or less heterogeneous collection of elements, and also, in some measure, to bring out the deftness of the subject in handling cards.
The third test was a cancellation test. The subject was requested to cross out, with a pencil, every 7. The fourth was a simple “Easy Directions” test. The fifth was a number-checking test, in which the subject was asked to place a check opposite every group which contained both a 7 and a 1. The sixth test was a tapping test, in which the subject was required to push down, as rapidly as possible, a telegraph key to which was attached a counter. The number of recorded thrusts over a period of one minute constituted a record for that performance. The seventh test was an accuracy test. This was given with the aid of a brass plate with nine holes, graduated in size from ½ inch to ⅛ inch in diameter. The subject was asked to take a brass-pointed pencil and insert it into each hole, beginning with the largest and continuing through the smaller ones, until the pointer touched the brass side of one of them. The brass-pointed pencil was wired in circuit with the brass plate containing the holes so that, whenever the brass point touched the side of the hole or any part of the brass plate, an electric contact was made which produced a click in a telephone receiver which the subject held to her ear. At the start of the test, the subject was instructed to put the brass pencil into each hole in succession until she heard a click in her ear, when she was to start all over again. The speed of the subject’s movements was controlled by a metronome, so as to allow thirty trials per minute. This test occupied from two to three minutes.
The eighth test was a steadiness test. This consisted of two brass bars about twelve inches long, set so as to form a long, horizontal V. The subject was asked to take the brass pointer and pass it along between these two bars. The farther she went, the narrower became the space between the bars. As soon as the brass pointer touched one of the bars it produced a click in the telephone receiver. The point at which this brass pointer touched was then read on a scale on the lower bar. Each subject was given fifteen trials and the last ten were averaged and constituted the subject’s average.
These eight tests were given to seventy-three girls, fifty-two of whom were inspectors and twenty-one gaugers. The scores in the tests were compared with the average daily work of the girls. This average was obtained by recording the number of pounds of shells inspected by the girls and the number of hours required for the work. It was found that the inspectors who inspected the largest number of shells in a given time attained the largest scores in the tests, thereby indicating the value of the tests in determining whether an applicant for work as an inspector had the mental capacity for the work.
The same tests were given to the twenty-one girls engaged in gauging the head-thickness of shells. This work does not require the use of the eyes. The operator simply picks up a handful of shells and, with or without looking, tries the head of each shell on a gauge. The gauge is a piece of steel with two notches or openings. The shells which are too small pass through the first opening and fall into a box of rejects below. Those that do not fall through are tried on the second opening and, if they pass through, they are of the right size. If they fail to pass through they are too large and are thrown aside. The operator sits in front of her gauge and tries each shell at one opening and then another, just as rapidly as she can move her hands up and down.
The tests showed, in this instance, an entirely different set of correlations. The comparative correlation scores follow:
| TESTS | INSPECTORS | GAUGERS |
|---|---|---|
| Card Sorting | .55 | .05 |
| Tapping | .14 | .52 |
| Cancellation | .63 | .17 |
| General Intelligence | .14 | .18 |
| Number Group Checking | .72 | —.19 |
Perfect agreement between average daily work and score in the test would be indicated by a correlation score of 1.00, while lack of relationship would be indicated by a correlation of 0 or nearly 0.
The score of the gaugers in the tapping test (.52) showed that they were speedier and had greater endurance. This seems reasonable since, in the operation of gauging, speed of movement and endurance are the chief factors. In the visual discrimination tests, such as card sorting, cancellation, and number group checking, the scores of the inspectors were higher. This quality, however, was not necessary to successful operation in gauging.