RELATIONS OF EXPERIMENTAL PSYCHOLOGY 673 



result of formative influences which can be expressed only in terms 

 of will and personality. But this is a part of the truth only. Above 

 the infinite variations which the universe of personalities presents 

 arise the types which their common features compose; and wherever 

 individuals are to be treated as a class the results of science, whether 

 physical or mental, are available in manipulating them. Enlight- 

 ened educational method is psycho-technical as well as inspirational, 

 and necessarily involves a sensitive regard for the whole set of 

 extrinsic conditions under which development takes place. To 

 know the influence of air-space, light, exercise, and food upon 

 human life and activity is part of the teacher's business. To under- 

 stand the relation of respiration, posture, digestion, and nutrition 

 to mental work is part of his business. To recognize the bearing of 

 atmospheric changes, in temperature, humidity, pressure, and 

 electric condition is part. The discharge of his office calls also for 

 an understanding of the consequences of nervous instability, excite- 

 ment, and depression; of the bearing of attitudes of hope, anxiety, 

 confidence, trust, and suspicion, and of the significance, in a word, 

 of the whole series of psycho-physical changes which take place in 

 the individual in connection with specific alterations in his sur- 

 roundings, condition, and prospects. And these are in large part 

 worked out by the experimental psychologist as supplemental 

 to his more immediate task of ascertaining the norms of mental 

 function and thereby establishing criteria by which the treatment 

 of classes of individuals may be intelligently controlled. 



