THE BEHAVIOR OF COCKROACHES 



87 



failures, refer to two factors concerned in the process of learn- 

 ing: practice and fatigue. 



The curves of the second series (Fig. 3) resemble those just 

 described in that they also show two crests. The difference 

 consists in the small number of shocks necessary to obtain 

 definite results of learning. This circumstance, however, brings 

 it near to the curves of the first series. Thus the curves of the 

 second series take an intermediate position between the two 

 others. 



/fO 



9 



& 

 7 

 6 

 5 



3 



2 







JO 



10 



30 



<i0 



Figure 3. Representation of the reactions of cockroaches Xos. 1 and 9. 



The results of an analysis of the curves enables us to separate 

 the cockroaches tested with respect to their ability in learning, 

 into three groups as shown in the following table. 



Characteristics of 

 the curve 



Short 

 One crest 



Short 

 Two crests 



Very long 

 Two crests 



Characteristic features of the 

 cockroaches in learning 

 Rapid progress with practice 

 Slow fatigue 



Rapid progress with practice 

 Rapid fatigue 



Slow progress with practice 

 Rapid fatigue 



The analysis of the curves and the possibility of isolating 

 two factors, practice and fatigue, permit us to assert that the 

 learning-curves of cockroaches may be considered a special 

 case of Kraepelin's "Arbeitscurve." 5 



6 Kraepelin. Die Arbeitscurve. Phil. Studien, 1902, Bd. 19. S. 459-507. 



