ON THE ABILITY OF ANIMALS TO KEEP TIME 

 WITH AN EXTERNAL RHYTHM 



WALLACE CRAIG 



University of Maine 



The habit of keeping time with an external rhythm, as in 

 singing, dancing, and marching, is an interesting and important 

 phase of human behavior. To what extent are similar habits 

 found among the lower animals ? A series of notes reporting 

 observations that bear on this question have appeared in Science. 

 But some of them have been uncritical, and the whole problem 

 needs to be carefully analyzed. 



To begin with, all non-rhythmic activities should be ruled 

 out as having no bearing on the topic. Certain flocks of birds 

 in flight turn this way and that with a speed and a simultaneity 

 which are remarkable to witness. But their turnings do not 

 recur in a regular rhythm; if they did so, they would constitute 

 a very different and much more complex form of behavior. 



As to rhythmic activities. All or nearly all animals keep 

 time with slow rhythms, as the rhythm of day and night, and 

 their ability to do so is an interesting topic in itself. But so 

 far as behavior is concerned these slow rhythms belong in a 

 different class from the quick rhythms here discussed, such as 

 those of locomotion, of song, and of the flashing of fireflies. 

 The slow rhythms often have nothing to do with the nervous 

 system; in human consciousness they are not perceived as 

 rhythms; and they may be left out of the present discussion. 



As to the rhythms which are under discussion; there are 

 some cases in which it is certain that animals do keep time with 

 an external rhythm, but they are cases in which there is a direct 

 mechanical connection between the moving parts of the animal 

 and the external object with which it keeps time. A familiar 

 example is the swinging of a canary on a swing perch. Some 

 spiders (e.g., Argiope) swing on their webs in a way which seems 

 to show that they time their movements with the rhythm of 

 the web. Newman (8) and Wheeler (10) observed that certain 

 Phalangidae gather in great clusters with their legs interlocked; 

 when some individuals are disturbed they set up a swinging 



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