CONDITIONING 89 



Furthermore, we may wish, to determine what the performance 

 in terms of the probabiliy of a correct response would be if, after n' 

 trials, the experiment is discontinued for some interval of time. The 

 addition of a single parameter enables one to determine the perform- 

 ance in terms of the various experimentally controlled variables. One 

 can then also determine the time required for the performance to drop 

 to some preassigned level. It is found, for example, that while in- 

 creasing the number of trials beyond some value has little or no effect 

 on the performance at the time, it may have a considerable beneficial 

 effect on the performance at some subsequent time. This is essen- 

 tially what occurs in overlearning. 



But these results apply only to the case of recognition-learning 

 as we have assumed that the stimulus to which response is to be made 

 is present at the time of choice. A generalization of the results can 

 be made so as to include the case of recall-learning (Landahl, 1943). 

 A number of parameters must be introduced in this case, but also two 

 new experimental variables enter. One variable determines whether 

 the experiment is that of recognition or recall. The other variable is 

 the number of correct responses, as in this case c cannot be deter- 

 mined from c = n + w due to the "equality" response, which in this 

 case is a lack of response. Thus with a small number of parameters 

 specified experimentally, c and w can be determined for various values 

 of the seven other variables and the result may then be compared with 

 experiment. 



