THE QUARTERLY REVIEW OF BIOLOGY 



vised, if indeed it ever can be. The news- 

 paper headliner to the effect that we had 

 found the dog equal in intelligence to a 

 child of six or eight years of age must have 

 been invented by the printer's devil. Or 

 perhaps it originated from a dullard's 

 confusion in connection with a statement 

 once made by Mr. Herbert that the dog 

 understood as many words as a child of 

 this age. The newspaper publicity began 

 when Mr. Herbert came out to Columbia, 

 at our request, to make a demonstration 

 performance (not a test) before a class of 

 graduate students in comparative psychol- 

 ogy. The press got wind of this demon- 

 stration and attended in a body, and the 

 next day five of the principal producers 

 of movie news reels were on hand with 

 their usual irresistible insistence. 



Although Mr. Herbert and Fellow were 

 very busy a short series of tests to be carried 

 out in the psychological laboratory at Col- 

 umbia was arranged. It seemed desirable 

 to repeat the test designed to rule out the 

 possibility of visual cues, under better 

 controlled conditions (that is, with no 

 one at all present during performance) and 

 to secure data regarding the total number 

 of words to which the dog would thus 

 respond. Furthermore, we wished to 

 test the ability of the dog to identify and 

 retrieve a given object from among several 

 upon command. The usual stage per- 

 formance of Fellow is from 10 to 30 

 minutes whereas our test periods ranged 

 from one to two hours, since we wished 

 to secure as much data as possible at such 

 times as the dog could be placed at our 

 disposal. The use of long test periods 

 was unfortunate inasmuch as Fellow often 

 gave every indication of being weary of 

 his task before the end of the longer 

 periods, although continuing to work 

 when duly encouraged by his master. 

 Aside from the word "Shame" or "That's 

 no good," spoken in a somewhat scolding 



tone, no punishment has ever been used 

 either in training or testing the dog. 



In re-test ing the dog's ability to respond 

 to commands in the laboratory Mr. 

 Herbert and both experimenters were 

 concealed behind screens so that there was 

 no opportunity whatsoever for the Clever 

 Hans error to enter into the results. 

 Several chairs, tables, and such other ob- 

 jects as were to be used, were placed in 

 chance locations about the room, which 

 included also two windows and one door. 

 The behavior of the dog was observed 

 through a slit in the screen by one observer 

 and recorded, while the other reported to 

 Mr. Herbert and indicated the command to 

 be given next. Reaction times were not 

 taken in this series of tests. On all three 

 days the command-performance test was 

 given after Fellow had been working for 

 an hour or more at the retrieving-objects 

 test, to be described later, and naturally 

 he was not at his best on all occasions. 



It soon became apparent that certain 

 commands could be carried out as per- 

 fectly under our test conditions as when 

 the master was present but that others 

 could not. After some attempt at analysis 

 we discovered that the repertory of com- 

 mands classified readily into two quite 

 distinct groups. Type I, as listed in table 

 1, did not involve any very definite iden- 

 tification of object or place, but consisted 

 of some movement of the animal's body 

 in whatever place he happened to be at the 

 moment. Type II, on the other hand, 

 required the animal to identify and orient 

 himself toward some object or place after 

 the command had been given. The for- 

 mer response could be made immediately 

 after the command issued, the latter 

 usually involved a delay of considerable 

 length. In fact, it constituted a typical 

 delayed reaction situation except for the 

 fact that the signal was a sound, or word 

 instead of a light and presupposed that a 



