J. The Social Use of Space 



19 



about the place where the trip terminated. Two hundred and fifty-six of 

 the total 2357 trips studied with reference to the initial period of hyper- 

 activity, terminated in such vacillations. As graphically shown in Fig. 7 

 the probability of vacillating is proportional to the length of the trip. 



5 10 



LENGTH OF TRIP IN FEET 

 Fig. 7. Probability of trips including a period of vacillation, wandering back and 

 forth about the point of termination. Curve based on 2,357 trips by 136 rats during their 

 first 150 minutes in the Fergu.son Activity- Alley. 



These results are given here because of their bearing on the question of 

 the proportion of time an animal is capable of responding to static compo- 

 nents of its environment. As I have stated above, I am proceeding with this 

 formulation, utilizing the hypothesis that directed responses can be made 

 only at the ends of periods of diffuse activity, which are represented here 

 by the outward termination of trips. If this responsiveness at ends of trips 

 persists throughout the wandering about at the end of trips, then it follows 

 that the farther a familiar type of object is from home the more likely it 

 will be responded to in proportion to trips terminating there. This conclu- 

 sion is subject to the (jualification that the object is so sparsely distributed 

 in space as to require more searching than mere detection of the surround- 

 ings at the point of terminating a trip. 



IV. Use of a Two-Dimensional Field 



A. Theoretical Origin 



We are here considering animals whose movements emanate from a fixed 

 home base. For them a two-dimensional field differs from a one-dimensional 



