178 



OTTO C. G LASER 



INTRODUCTION OF ADDITIONAL STIMULI 



The "tank experience" may be complicated by the introduc- 

 tion of additional factors, which, classified by their effects, may be 

 called retarding and accelerating stimuli. Marked accelerations 

 were produced by allowing the animals before reaching the water 

 in the tank, to fall through a paper bag filled with water consider- 

 ably warmer; also if, during their fall through the cylinder, the 

 animals received an electric shock, the speed was increased. On 

 the other hand, the addition of salt in small quantities to the water 

 in the tank had, on the average, a depressing effect. The most 

 marked, as well as constant effects, however, were go+ten by the 

 system of desired rewards. Animals that had been without food 

 for twenty-four hours, were dropped into disagreeably cold water, 

 and immediately on escaping, were wrapped in warm towels and 

 given a nibble of cheese. All these factors helped to make escape 

 from the tank better worth while than it had been in any of the 

 preceding experiments. The results, based on two full-sized 

 adults, and on eight young, less than a year old, are tabulated 

 below. As heretofore, the adults are labelled with capitals, the 

 young with small letters. 



Not only are the adults too few, but the number of trials made 

 is too small to allow of satisfactory comparison with the earlier 

 records made under simpler conditions. Neither AA nor BB 



