562 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



ferences can not be improved appreciably by practice. They dis- 

 tinguish sharply between the cognative and physiological thresholds. 

 The cognative threshold shows rapid improvement at first and ap- 

 proaches the physiological threshold just to that degree that the 

 subject is able to grasp the nature of the test, to understand thoroughly 

 what is required of him, remove subjective disturbances, expectations, 

 and inhibitions, and to summon his best effort and most favorable 

 attention to the discrimination of the pitch of the tones presented. 



These experimenters believe that a 1-hour group test by the hetero- 

 geneous method (that is, a number of individuals who have not been 

 classified in reference to their pitch discrimination ability, tested with 

 a number of pitch differences ranging in size from 30 to 1 vd.,^ and 

 each increment presented for judgment about an equal number of 

 times) will reveal the approximate physiological threshold of about 

 half of the subjects tested. The elimination of all objective disturb- 

 ances, careful instruction, and the ingenuity of the experimenter 

 count for much. 



In using pitch discrimination as a measurement in the present 

 research, it was not hoped to make an accurate determination of the 

 physiological threshold of the subjects tested to ascertain if food 

 reduction changed this physiological constant. The time would not 

 permit of using the measurement in any other way than by the group 

 method. In the first test with each squad pitch difference incre- 

 ments of 30, 23, 17, 12, 8, 5, 3, 2, and 1 vd. lower than 435 vd. were 

 employed. The test lasted about one-half hour. Judging by pre- 

 vious experience with pitch discrimination measurements, the condi- 

 tions were favorable. Nearly all the sub j ects were able to discriminate, 

 without error, differences above 8 vd. In succeeding tests it was there- 

 fore possible to confine the judgments to intervals of 8, 5, 3, 2, and 1 vd. 

 It would have been possible also to have omitted the increment of 

 8 vd., since nearly all subjects show from 90 to 100 per cent correct 

 judgment with this pair of tuning forks. It was, however, advan- 

 tageous to use this increment in the test because of the easy assurance 

 with which the subject was able to judge between these tones. This 

 gave confidence for the more difficult judgments. 



In tables 149 and 150 for Squads A and B, respectively, the per- 

 centages of correct judgments are given for the pitch increments 5, 

 3, 2, and 1 vd.^ The tables are of the same general form as those given 

 for steadiness of tracing. Thus in table 149 Bro on October 13 shows 

 97 per cent correct judgment with a pitch difference of 5 vd., 90 per 

 cent with a difference of 3, 80 per cent for 2, and 63 per cent for a dif- 

 ference of 1 vd. This was the second trial in pitch discrimination 



* Double vibrations. 



^ It appeared unnecessary to include the results for 8 vd., as the percentage of correct judgments 

 with this interval was usually well above 90. 



