For the higher levels of intelligence, especially, the test is superior to that of repeating digits in the direct order. It is less mechanical and makes heavier demands upon higher intelligence.
Average adult, 6: using a code
Procedure. Show the subject the code given on the accompanying form. Say: “See these diagrams here. Look and you will see that they contain all the letters of the alphabet. Now, examine the arrangement of the letters. They go (pointing) a b c, d e f, g h i, j k l, m n o, p q r, s t u v, w x y z. You see the letters in the first two diagrams are arranged in the up-and-down order (pointing again), and the letters in the other two diagrams run in just the opposite way from the hands of a clock (pointing). Look again and you will see that the second diagram is drawn just like the first, except that each letter has a dot with it, and that the last diagram is like the third except that here, also, each letter has a dot. Now, all of this represents a code; that is, a secret language. It is a real code, one that was used in the Civil War for sending secret messages. This is the way it works: we draw the lines which hold a letter, but leave out the letter. Here, for example, is the way we would write ‘spy?’” Then write the word spy, pointing out carefully where each letter comes from, and emphasizing the fact that the dot must be used in addition to the lines in writing any letter in the second or the fourth diagram. Illustrate also with war.
Then add: “I am going to have you write something for me; remember now, how the letters go, first (pointing, as before) a b c, d e f, g h i, then j k l, m n o, p q r, then s t u v, then w x y z. And don’t forget the dots for the letters in this diagram and this one” (pointing). At this point, take away the diagrams and tell the subject to write the words come quickly. Say nothing about hurrying.
The subject is given a pencil, but is allowed to draw only the symbols for the words come quickly. He is not permitted to reproduce the entire code and then to copy the code letters from his reproduction.
Scoring. The test is passed if the words are written in six minutes and without more than two errors. Omission of a dot counts as only a half error.
Remarks. It is not easy to analyze the mental functions which contribute to success in the code test. Contrary to what might be supposed, success does not necessarily depend upon getting and retaining a visual picture of the diagrams. Kinæsthetic imagery will answer the purpose just as well, or the original visual impression may even be translated at once into auditory-verbal imagery and remembered as such. The significance of the test must be expressed in other terms than the kind of imagery it may happen to bring into play.
Healy and Fernald describe the task of writing a code sentence without copy as one which requires “close attention and steadiness of purpose.” They also emphasize the fact that the attention must be directed inward, since there is no object of interest before the senses and since no special stimulus to attention is offered by the experimenter. Observations we have made on subjects during the test confirm this view as to the factors involved.
That inability to remember the code as a whole is not a common cause of failure is shown by the fact that subjects above 12-year intelligence who have failed on the test are nearly always able to reproduce the diagrams and insert the letters in their proper places. To give the code form of a given letter without copy, however, makes a much heavier demand on attention. Nearly all subjects find it necessary to trace the code form, in imagination, from the beginning up to each letter whose code form is sought. Subjects of superior intelligence, however, sometimes hit upon the device of remembering the position of the individual key letters e.g. (the first letter of each figure) from which, as a base, any desired letter form may be quickly sought out.
The test correlates well with mental age, but for some reason not apparent it is passed by a larger percentage of high-school pupils than unschooled adults of the same mental level.