GROUP BEHAVIOR 163 



ever the fish came forward through the gate they 

 were offered pieces of worm soaked in acetic acid. 

 The isolated fish, perhaps because they had not 

 learned to perform so well, perhaps because they 

 were isolated or for some other reason, ceased to 

 react rapidly, and on the twenty-ninth day they were 

 averaging fifteen minutes per trial. The grouped 

 fish were much more steady in behavior, and per- 

 sisted in coming forward with relatively little change 

 until the twenty-seventh day; and even then the old 

 conditioning held for most of the fish most of the 

 time. Many individuals persisted in coming forward 

 through the gate for a long time after they ceased 

 biting or even swimming toward the acid-treated 

 worm. 



When a group of fish are reacting together, if a 

 given individual moves forward through the gate to 

 the feeding space, others may follow because of a 

 group cohesion. It is obvious that if a fish is isolated 

 and moves forward, the faster reaction cannot affect 

 the behavior of other isolated fish. 



With this in mind. Dr. Welty undertook a series 

 of experiments in which there were two partitions 

 in the aquarium, with one door opening forward 

 and another door opening through the other parti- 

 tion toward the rear of the aquarium (Figure 34). 



