ON SOUND DISCRIMINATION BY CATS 73 



of being aware that it had made a mistake. In a test of ten 

 trials on the following day, Pet made no mistakes. 



3. Discrimination of the Difference of Two Octaves of Pitch 

 on a Piano; i.e., between F-l, Bass Cleff, and F-2, Treble Cleff. 

 Fed at F-l. Not fed at F-2. 



Pet. — On the first day of this experiment, in twenty trials, the 

 cat reacted to A-l thirteen times and to A-2 three times. Its 

 wrong responses to A-2, were in the first, second and fifteenth 

 trials. On the second day of the' experiment (three days later), 

 in twenty trials, or with forty trials in all, Pet responded to A-l 

 twenty times and to A-2 none. In the first trial on that day, 

 the animal got up slowly at the food-note, as if in some doubt 

 what to do. In the remaining nineteen trials correct responses 

 by the cat were prompt. 



4. Discrimination of Noise. 



The animal was placed in the cage as in the preceding experi- 

 ments on pitch discrimination. The sound apparatus consisted 

 of a wooden box, 18 x 11 x 10 inches, and a slat 13 x 4 x tV 

 inches, fastened to the top of the box by a leather hinge. By rais- 

 ing the free end of the slat and suddenly letting it go, it struck the 

 top of the box and made a sound varying in loudness with the 

 force with which it struck. To give sounds of different degrees 

 of intensity or loudness, two sticks, one 2\ inches in length, the 

 other 4+ inches, were separately used and placed perpendicular 

 to the box, under the free end of the slat. By pressing on the 

 slat near the hinge and suddenly removing the shorter stick, the 

 slat would strike the box and produce a sound of noticeable 

 intensity, and by using the longer stick in a similar manner, a 

 louder noise was made. The same pressure, as nearly as possible, 

 was exerted on the slat in both cases. By rearing up and looking 

 through the top of the cage when the louder noise was made, the 

 animal was to show its discrimination of the louder and lesser 

 noises. It was fed at the louder noise and not fed at the lesser. 

 The noise apparatus was manipulated at the closed side of the 

 cage, so it was not possible the reactions were to stimuli other 

 than the sounds. The noises were made in an irregular order. 



Pet. — On the first day of the experiment, in twenty trials, the 

 animal reacted to the food-sound, the louder noise, eight times, 

 to the lesser noise four times and with three doubtful responses. 



