THE BEHAVIOR OF COCKROACHES 



85 



While 1 6 shocks were sufficient for No. 4, No. 10 performed 

 the ten obligatory turnings back only after having received 

 118 shocks. It may therefore be assumed from the different 

 manners of learning that there were three types of cockroaches. 



Let us mark the curves of learning based upon the results 

 gained with the ten cockroaches. In all the curves, abscissas 

 represent the number of shocks; and ordinates the number of 

 the turnings back without receiving a new shock. Figure 2 

 shows the curves of Nos. 2, 4, 6, 7 and 8; Figure 3, those of 

 Nos. 1 and 9; Figure 4, those of Nos. 3, 5 and. 10. 



The curves of the first series (Fig. 2) are similar in char- 

 acter, since they ascend successively till the crest is attained. 

 The number of shocks necessary for producing the definite 

 result is rather small. These data, however, prove that after 

 the first experience of the shock, the animals made continuous 

 progress. Thus the curves show no important or prolonged 

 failure. 



Fig. 4 represents the curve of the third series. This curve 

 is much longer and shows that the animals learn only after 



