222 INTELLIGENCE IN LOWER VERTEBRATES 



augmented if the tube was placed in a different part of the 

 aquarium or by feeding the fish with a few of the worms. 

 That fish readily associate certain stimuli with food has 

 been shown by several observers. Herrick found that 

 catfish which at first would seize pieces of cotton which were 

 brought in contact with its barbels would gradually cease 

 to react to them. After a few trials the fish would make a 

 movement toward the cotton, but it was soon checked. 

 Finally the cotton could be rolled over the barbels or other 

 parts of the body without eliciting any response. The 

 fish probably recognized the cotton through the sense of 

 touch as it made little difference if, at any time, red cotton 

 was substituted for white. Washburn and Bentley in their 

 experiments on the creek chub showed that this fish is able 

 to associate different colors such as red and green with food. 

 The chub in one set of experiments was fed out of a pair of 

 red forceps which were let into the water alongside of a green 

 pair. Although a meal worm was placed in the red pair the 

 fish often snapped at the green forceps first, but after a num- 

 ber of trials the green forceps were ignored. When the fish 

 had been given a number of worms the forceps were put in 

 empty. The fish continued to snap at the red pair and 

 avoid the green regardless of their relative positions. Red 

 and green forceps of different degrees of brightness were 

 used and precautions were taken to eliminate the in- 

 fluence of odor, but in the last 40 experiments in which no 

 food was placed in either forceps and the relative position 

 of the forceps exchanged after each trial the fish snapped at 

 the red pair every time. It is probable, therefore, that the 

 chub is able to distinguish colors as opposed to mere differ- 

 ences in brightness although the proof of this is not en- 

 tirely conclusive and it is very evident that it is able to 

 form associations with a fair degree of rapidity. 



