122 VINNIE C. HICKS AND II. A. CARR 



capacity, this peculiarity of behavior is not necessary and, as 

 a consequence, this tendency is repressed. 



The relative validity and importance of these three explana- 

 tory concepts is immaterial to this paper. We are interested 

 in maintaining the reasonableness of the assumption of a causal 

 relation between intelligence and the surplus values. The 

 proposition that the total values constitute the best single index 

 of intelligent capacity is also rational from another point of 

 view. The surplus values eliminated represent the amount of 

 exploration, or the amount of motor effort, necessarily involved 

 in the mastery of the problem. It is a customary assumption 

 that the ability to master a task is inversely proportionate to 

 the effort necessarily involved, and that the quantitative estima- 

 tions of the amount of effort expended serve as the best criterion 

 for judgments of comparative ability. In memory experiments 

 of the Ebbinghaus type, the conditions are so arranged that 

 the comparative amount of work expended by two subjects is 

 best expressed by the " number of repetitions or trials." The 

 same procedure would also apply to problems of the maze type, 

 provided all trials were equal as to the effort involved. Obviously, 

 the trials are utterly disparate in this respect and as a conse- 

 quence the " total values " is the only aspect of the curves 

 which represents in any adequate manner the factor of " effort." 

 In this connection it is well to note that the " total values " 

 also represent in a way the " number of trials," for, to a cer- 

 tain extent, the surplus values must vary with the number 

 of trials. 



The factor of " surplus values " cannot, however, be regarded 

 as a very accurate or delicate index of intelligent ability, (a) 

 While it is the only representative of the " amount of effort 

 expended," yet it can not be considered as an adequate repre- 

 sentative. The time and error values are directly propor- 

 tionate to the motor effort, but their relations to any effort 

 of an intellectual sort is more complex. The time values may 

 be regarded as measuring the amount of mental work so far 

 as its duration is concerned, but, as we have noted, the two 

 are inversely related in respect to the degree or efficiency ofthe 

 mental processes, (b) When the criterion is based upon the 

 time and error values, the ratios between the three groups are 



