RESPONSES TO LIGHT OF THE ROACH. 



379 



uniformity, all of the tabulations were made from experiments 

 performed with box number two. 



In every case, sooner or later, the roach always learned to avoid 

 entering the dark chamber; and this was true whether I used 

 discrimination box number one or discrimination box number two. 

 With box number one, where greater freedom was allowed, it 

 usually required more time to establish the habit. As a group 

 adult male roaches learned to avoid the dark chamber more 

 quickly than adult females and young females much more quickly 

 than old females. The slowest of all of the roaches to learn 

 were adult females with amputated antennae (Fig. i). 



D 



B C 



FIG. i. Learning curves of roaches. Each of these curves represents the 

 average of ten roaches of the kind indicated. The abscissas represent electric 

 shocks, the ordinates the number of refusals to enter the dark chamber that were 

 made before receiving the next shock. A represents adult female roaches; B, adult 

 male roaches; C, larval females one half inch long; D, larval females one fourth of 

 an inch long; E, adult females with amputated antennae. 



There is a marked contrast between the behavior of adult 

 roaches with amputated antennae and ordinary adults. The 

 normal roach usually moves along the middle of the passageway 

 until it reaches the entrance to the dark chamber, which it either 

 enters or refuses to enter. Before receiving punishment these 

 movements are rapid; after receiving one or more shocks, the 

 roach moves along more slowly and more cautiously. If it 

 approaches the sides at all it is for the purpose of attempting 



