1. The Social Use of Space 



93 



In addition the endedness of the environment biased movement. After 

 some period of time every rat tended to leave the pen it was then in and 

 go into an adjoining pen. Rats in an end pen could only go to the adjoining 

 center pen, while a rat in one of the two center pens could go to the other 

 center pen or to the adjoining end pen. In other words, when a rat is in an 

 end pen it has a probability of 1.0 of going into the adjacent center pen, 

 but if it is in a center pen it has a probability of 0.5 of going into the adja- 

 cent end pen or 0.5 of going into the other center pen. Repetition of shifting 

 by all members by the operation of this principle alone soon leads to a 



z> 0.5 



PEN 

 lor HI 



I *********** ******* *' 



ASONDJFMAMJJ 

 1958 MONTH 1959 



Fig. 33. The upper portion of the figure represents in schematic fashion the environ- 

 ment in which large social groups of albino rats were maintained. See text for details. 

 The lower figure contrasts the amount of food consumed in the most used and the least 

 used pen from the inception of the behavioral sink during the sixth month (August, 

 1958) of the study. 



steady state in which a 1:2:2:1 ratio will characterize the density of rats 

 across pens I: II: III: IV. See pages 298-299 of Calhoun (1962a) for details 

 of the mathematics involved in the origin of this ratio. 



Populations in four such 4-pen environments were studied from Febru- 

 ary 1958 to July 1959. By the eighth month, September 1958, each popu- 

 lation consisted of three generations, each artificially fixed at near 30 in- 

 dividuals. The first and second generations were sexually adult, and the 

 thu-d was recently weaned. Distribution of adults at this time proved to 

 be of considerable importance in producing a phenomenon I have termed 

 a "behavioral sink." Five surveys of place of residence gave a total count 

 by pen of 343 for pen I, 467 for pen II, 331 for pen III, and 245 for pen IV. 



