The first week A^{1-4} were given, the second week A^{5-8}, etc., so that each week one series of each of the four types was given the subject.

In place of foreign symbols the numbers from 1 to 99 were used, except in A^{13-15}, in which three-figure numbers were used.

Each series contained seven couplets, except A^{13-16}, which, on account of the greater difficulty of three-figure numbers, contained five.  Each couplet was composed of a number and a noun, object, verb, or movement.

Certain rules were observed in the composition of the series.  Since the test was for permanence, to avoid confusion no number was used in more than one couplet.  No two numbers of a given series were chosen from the same decade or contained identical final figures.  No word was used in more than one couplet.  Their vowels, and initial and final consonants were so varied within a single series as to eliminate phonetic aids, viz., alliteration, rhyme, and assonance.  The kind of assonance avoided was identity of final sounded consonants in successive words, e.g., lane, vine.

The series were composed in the following manner:  After the twenty-eight numbers for four series had been chosen, the words which entered a given series were selected one from each of a number of lists of words.  These lists were words of like-sounded vowels.  After one word had been chosen from each list, another was taken from the first list, etc.  As a consequence of observing the rules by which alliteration, rhyme, and assonance were eliminated, the words of a series usually represented unlike categories of thought, but where two words naturally tended to suggest each other one of them was rejected and the next eligible word in the same column was chosen.  The following is a typical series from the A set.

   A^{1}.  Numbers and Nouns.

19     42     87     74     11     63     38
desk   girl   pond   muff   lane   hoop   vine

The apparatus used in the A set and also in all the later sets may be described as follows:  Across the length of a table ran a large, black cardboard screen in the center of which was an oblong aperture 14 cm. high and 12 cm. wide.  The center of the aperture was on a level with the eyes of the subject, who sat at the table.  The aperture was opened and closed by a pneumatic shutter fastened to the back of the screen.  This shutter consisted of two doors of black cardboard sliding to either side.  By means of a large bulb the length of exposure could be regulated by the operator, who stood behind the table.