278 CARL W. BOCK 



In amplification of the above, Swindle's observations on certain 

 animals may well be cited. He observed that certain owls 

 (Glaucidium whitelei Lws.) made characteristic periodic to and 

 fro movements with the tail. More concretely stated, the owls 

 moved the tail to and fro a certain number of times and then 

 stopped; after a pause of variable duration they made similar 

 movements and rested, and so on throughout longer periods of 

 observation. Other animals behaved similarly, some using this, 

 others that member of the body, or limb, for the performance of 

 these group movements. 



By definition any series of periodic movements of the same 

 body members is called a group, and any single to and fro move- 

 ment, a beat or an element of a group. Moreover, if the group 

 consists of 5 elements or 8 elements, or 23 elements, etc., it 

 is respectively known as the 5-group, 10-group, 23-group, etc., 

 to distinguish it from groups which contain any other number 

 of elements. 



The term group had however another justification than that of 

 merely defining or describing a series of similar periodic move- 

 ments. It had a functional or behavioral justification which 

 was based upon the fact that certain groups recurred very fre- 

 quently in the same animal, and indeed far more frequently 

 than would be expected, were the frequency of recurrence only 

 a matter of chance. In consequence of the apparent stability 

 of these activities the term group carries with it the implication- 

 that groups are entities of some kind, functional units of perhaps 

 the same order as the more traditional functional units commonly 

 called reflexes, instincts, and habits. Indeed, Swindle identi- 

 fies groups with instincts and habits accordingly as they are 

 inborn or acquired. 



The observers whose data constitute the basis of the present 

 study were human beings. They were instructed by the writer to 

 beat periodically on the button of a tambour as long as they de- 

 sired to do so : to rest as long as they had previously beat : and 

 finally, so to alternate beating and resting until instructed to 

 cease. No limitations were placed on the periodicity of their 



