Yerkes and Dodson, Habit Formation. 



467 



of the primary current. The primary current used for the experi- 

 ments of sets II and III measured 1.2 amperes, hence the value 

 of the stimulating current which was obtained when the secondary 

 coil stood at o was 350 X 1.2 = 420 units of stimulation. 



Fig. 3. Calibration curve for Porter inductorium. The numbers below the base line refer to the 

 position of the secondary coil with reference to the primary. The positions are read, as on the scale of 

 the inductorium, in centimeters. The numbers in the margin represent values of the induced current 

 in terms of Martin's unit of stimulation. 



As conditions for the experiments of set I, we chose three 

 strengths of stimuli which we designated as weak, medium, and 

 strong. The weak stimulus was slightly above the threshold of 

 stimulation for the dancers. Comparison of the results which it 

 yielded with those obtained by the use of our calibrated inducto- 

 rium enable us to state with a fair degree of certainty that its value 

 was 125 db 10 units of stimulation. The strong stimulus was decid- 



