The apparatus for the word-reaction measurement comprised a kymograph with a circuit breaker (fig. 27, C, the movable contact), a Deprez signal magnet, an exposure apparatus, and voice key. The general arrangement of the apparatus is illustrated in figure 31. The Deprez signal marker is seen above and in contact with the kymograph.2

1 In the stimulus apparatus previously used, the fixation mark disappears at the instant when the true stimulus comes into view. This gives the eye the impression that the fixation mark has shifted position rather than that something new has appeared.

2 Another signal magnet not distinguishable from the Deprez marker in figure 31 is used for control time on the kymograph. This marker comes in contact with the kymograph for a very short period every 2 seconds. This method of controlling the time was used by Dodge and has the unique advantage that while the time is on the record it is not conspicuous and does not complicate the other curves. See figure 28, page 157, for the wiring diagram, and figure 29, page 158, for sample record showing control time.

The exposure apparatus E (see figure 31, page 160) when used is slipped into position at the end of the kymograph and clamped to the post P. The stimulus words were visible to the subject through the window W. The voice-key V is connected with flexible cables and may be used in any convenient position. The voice-key is the one used by Dodge and Benedict, and described and figured by them in their publication.1 The exposure apparatus was also the same as that described by Dodge and Benedict in their figure 30, which shows the construction of the back of the apparatus not visible to the subject.

One modification which greatly facilitated the taking of reactions with this exposure apparatus was in the clip which holds the card in position for exposure at the end of the movable arm. A holder was substituted which would contain a pack of 25 cards, each card having a stimulus word printed on it. Thus, following a reaction, it was only necessary to lift the arm of the exposure apparatus and withdraw the card bearing the word which had just been reacted to; the apparatus was then ready for the next reaction when the movement of the kymograph shaft broke the circuit and caused the second stimulus word to come into view in the window. Previously, when it was necessary to put in a card before each reaction, as well as withdraw the one which had just been reacted to, it was not possible to take reactions faster than one in every 10 seconds. This made the measurement somewhat tedious, or at least it appeared so with certain subjects.2 With the pack arrangement of the stimulus cards it was easily possible to take reactions every 5 seconds, and had there been a convenient kymograph speed the time could have been still shorter without inconveniencing the subject or the experimenter.3

The position of the exposure device, with reference to the subject and to the other items of apparatus, is shown in figure 31. The subject sat in a position which would be at the extreme left in this figure. The voice-key V was held in the right hand and the arm was supported on a convenient rest not shown in the picture. Thus the moving kymograph drum and other distracting features of the apparatus were hidden from the view of the subject, as the exposure apparatus occupied the greater part of his field of view. The area about the window, where the stimulus words appeared, was a light gray.4

1 Dodge and Benedict, Carnegie Inst. Wash. Pub. No. 232, 1915, p. 99, fig. 16. Photographic records for the latency of the voice-key as connected with different signal markers, and for the pronunciation of different words are given by them in their figs. 17 to 20.

2 Miles. Carnegie Inst. Wash. Pub. No. 266,1918. p. 66.

3 Reference should be made to fig. 28. p. 157. for the wiring diagram for the word-reaction apparatus.

4In the previous of this apparatus (Dodge and Benedict. Carnegie Inst. Wash.'Pub. No. 232. 1915; Miles. Carnecie lost. Wash. Pub. No. 266. 1918) the exposure device was placed at the other end of the kymograph. (See Dodge and Benedict, p. 95. the lower right-hand corner of fig. 14.) The subject occupied the same position as in the research, and thus had the moving kymograph in his field of view when be was reacting to the words presented by the exposure.

Word reactions are illustrated in figure 29 (p. 158) in the portion of the record below the cross. Beginning at the bottom of the record and reading from the left, the first break in the line, designated as E, signifies the exposure of the word. The next upward movement of any one specific fine is the reaction. The peripheral velocity of the drum was 100 mm. per second. The reactions are very quickly read by placing a ruled glass plate over the record, and since the exposure positions formed a straight line as in the record illustrated, it is not necessary to move the plate to read each reaction in turn. In computing results adjustment was made for any inaccuracy in the speed of the kymograph. When the reactions were finished the experimenter took the voice-key in his hand and shook it gently. This produced a series of breaks in the line which is nearest the cross in figure 29, and served as a rough standardization for the action of the key.

Suitable illumination was provided at the back of the subject and directed over his right shoulder at the exposure apparatus at such an angle that reflected light was not troublesome to the eyes. The apparatus, as used, was very convenient to both subject and experimenter. The 25 reactions, including preliminary adjustments, require approximately 3 to 3 1/2 minutes. The subject was instructed to speak quickly and distinctly "each word that came into view." The words were all 4-letter, 1-syllable English words. Those employed were to some extent the same as had been previously used in other word-reaction and memory experiments. A subject was shown all the words to begin with before the first reaction measurements were taken. The same words were always used, but particular care was taken to keep the cards clean and the pack of cards was well shuffled before each trial. Thus, while the subject became thoroughly familiar with the words, he had no way of anticipating their order of exposure.