178 WALTER LOUIS HAHN. 



ered was usually slower and more cautious than when the senses 

 were unimpaired. 



In the cases where they flew against the screen that obstructed 

 the open window, the bats may have been attracted by incom- 

 ing currents of air. In experimenting with them in a closed 

 room they almost invariably found the cracks under doors, in 

 the sides of the room, or under the roof and the experiments 

 were seriously delayed by a large number of the animals escap- 

 ing through crevices which were overlooked or were supposed 

 to be too small for the passage of their bodies. They always ex- 

 plore every corner of any compartment into which they are placed 

 and their manner often indicates that they are attracted to an 

 opening from a distance of several feet when the air currents 

 are the apparent stimulus. 



II. TJie Fonnation of Associations and the Sense of Direction. 



The experiments described in this section deal chiefly with a 

 single kind of association, namely, that of place. In studying 

 this sort of association, data were obtained which seem to indicate 

 the presence of a sense of direction not based directly on any of 

 the five senses commonly recognized. 



The peculiar habits of a bat make it impossible to employ the 

 methods generally used by animal psychologists in studying the 

 formation of associations. Bats will not go to a dish for food at 

 regular intervals. Although they readily learn to escape from 

 any possible opening, they do not have any adaptation for grasp- 

 ing which would enable them to learn to pull a string or raise a 

 latch and so open a door. 



I did not find any evidence that associations of form or color 

 are ever formed. Such associations are hardly to be expected in 

 animals with visual organs so poorly developed. 



Sound associations are formed readily. A sucking noise made 

 by the lips at first alarmed the animals, but they soon learned to 

 associate it with feeding. On hearing it they would look about 

 and snap at any object that could be mistaken for food. One 

 individual (bat No. 2 mentioned below) was especially quick to 

 form this association and learned to come on hearing the sound, 

 although it did not learn to localize it definitely. Alcock ('99) 



