PSYCHOLOGICAL PROGRAM AND TECHNIQUE. 165 



mained unchanged.-^ The stimulus openings were arranged on four 

 axes passing through this fixation mark, that is, horizontal, vertical, 

 and at angles of 45°. The points were 2 mm. in diameter and on 

 any axis were arranged 3, 6, and 12 cm. from the central fixation 

 mark. In the four corners of the viewed field there were points 

 which were 15 cm. from the fixation mark. The field was 45 cm. 

 from the subject's eye. 



The stimulus device was perfectly satisfactory for our purpose, save 

 that occasionally some one of the shutters would fail to close completely. 

 In the measurements taken in this research and in many others made 

 previously no secondary criteria can be discovered as coming from the 

 stimulus apparatus. A slight sound due to friction can be heard when 

 a string is pulled to open a shutter previous to giving the stimulus for 

 reaction, but this sound is localized, as being behind the lamp house and 

 under the table. In this investigation the inner ring of stimulus posi- 

 tions, that is, those which were only 3 cm. from the fixation point, were 

 not used, nor were the positions vertically above and vertically below 

 the fixation position. This limited the number of stimulus positions 

 to 16, all of which were used with about equal frequency with any one 

 subject. 



Sample records of the eye reaction are reproduced full size in figure 

 36. The light which falls upon the subject's eye is interrupted by a 

 timing vibrator and so causes the photographic record to appear as a 

 row of short dashes. Each dash with one interspace is equal to 0.01 

 second. The records are to be read from the bottom upwards. AVhen 

 the line of dashes suddenly turns right or left it indicates that the eye 

 of the subject has moved in the direction of the stimulus light. The 

 number of dashes from the beginning of the record to the point where 

 movement begins gives the reaction time. The records illustrated are 

 from two subjects. Those shown in the right-hand plate are seen to 

 be, in general, longer and more irregular than the others. 



(10) Reaction Time for Speaking 4-letter Words. 



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.^ 



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 com- 

 plicate the other curves. See figure 28, page 157, for the wiring diagram, and figure 29, page 

 158, for sample record showing control time. 



