PSYCHOLOGICAL MEASUREMENTS. 611 



the average being 3.1 seconds. The higher threshold for October 13 

 may be partly due to the food reduction. The poor result for 

 November 10 corresponds with the lowest average net energy figure 

 for any of the experimental dates (see table 146). These corre- 

 spondences do not definitely prove that the reduced diet raised the 

 threshold for visual efficiency with Squad A, and as the results for B 

 give no clear substantiation, the findings appear to be negative. The 

 difference in level between the two squads can hardly be assigned as 

 a low-diet effect, although if each squad were several times larger, 

 this might be significant. 



(13) SENSORY THRESHOLD FOR ELECTRIC SHOCK. 



This measurement taken in the same way and employing the same 

 apparatus, with the exception of the electrodes,^ was used in the normal 

 series of 1917. The threshold range shown by the 63 normal men 

 was from 46 to 195 volts. The subjects were distributed in threshold 

 ranges as follows: 



50 or below. 51 to 75. 76 to 100. 101 to 125. 126 to 150. 151 to 175. 176 to 200. 

 1 3 13 23 16 5 2 



The distribution is seen to be a fairly normal one, the mode is 

 clearly at 101 to 125 volts, within which range 23 of the subjects 

 came. The average for the whole group was 117.3 volts, with a 

 standard deviation for the series of 63 subjects of 30 volts. 



With the above values in mind as normals for initial measurements, 

 we may turn to a consideration of the data for Squads A and B, as 

 shown in tables 177 and 178. For the first experiment, September 

 29, the 10 men of Squad A show an average of 118 volts as compared 

 to 117 volts for the normal series of 1917. That this close corre- 

 spondence is not entirely accidental is proved by the fact that Kon, 

 Spe, and Fre of Squad A, whose values are not included in the average, 

 show a similar average of 123 volts. The 10 men of Squad B in their 

 first experiment had an average of 126 volts, the one man whose records 

 are not in the average (Mac) having a value of 101 volts. It appears 

 that in initial measurements of the threshold for electric shock, with 

 the apparatus and technique here employed, a normal average value 

 of about 120 volts may be reasonably expected. Squad A (see table 

 177) for the nine experiments of October 13 to February 2, has also a 

 total average for the ten men of exactly 120 volts, suggesting that there 

 has been very little, if any, improvement in contrast to the visual 

 threshold results throughout the period of measurements. The 

 averages for the individual subjects, exclusive of September 29, range 

 from 69 volts for Moy to 172 volts for Mon. 



^The electrodes were also of the non-polarizable type, but separate vessels were provided for 

 each finger; the vessels being quite small, the level of the solution was adjusted for each subject. 

 The normal measurements were made in the summer and the salt solution was of room tem- 

 perature. It was unnecessary to warm it by the electric heater. 



