1. The Social Use of Space 11 



2. The Role of a Structured Environment on the Termination 

 OF Trips 



Natural habitats possess structures which elicit responses. Items of food 

 and nesting material represent structures normally causing animals such 

 as rats to terminate trips. When such items are transported home the trip 

 resembles the nonvacillating ones in the one-dimensional alley in the sense 

 that there is a direct outward phase, terminated by the object being picked 

 up, followed by a direct homeward trip transporting the item. In order to 

 explore the effect of such structuring in the one-dimensional habitat upon 

 termination of trips, one of two procedures was followed; At each one- 

 foot interval from home along the alley, there was placed a pad of paper 

 strips or an open hopper of food pellets. During any particular rat's stay 

 of 3-12 days in the alley, only nesting material or only food pellets were 

 available. Periodic replenishment of each source ensured a continuous 

 supply at each distance. Nevertheless, the rats removed items from each 

 distance (Table la) even though this necessitated passing by opportunities 

 to respond while on the outward journey. Each item removed at a particular 

 distance from home is considered to indicate a trip-termination at that 

 distance. Examination of the oscillograph record confirmed this inter- 

 pretation. 



The frequency of termination of such trips as a function of distance is 

 also described by the equation, y = exp (a -\- bx) . The slope for trips termi- 

 nated by picking up paper strips, 63, is —0.3027; while 64, the slope relating 

 to securing food pellets, is —0.2481. The t test, 



63 — hi 



= -2.128 



VVar. (63 - 64) 



has a p value between 0.05 and 0.01 which indicates a statistically signifi- 

 cant difference between these two slopes. However, examination of Fig. 4 

 reveals a marked dispersion about the best-fit line of the observed points 

 relating to nesting material. For this reason, the interpretation that the 

 63 and 64 slopes differ statistically is open to question that this difference 

 in slope implies biological significance. I therefore believe it wisest to as- 

 sume that 63 and 64 are really identical, or nearly so. 



If this is so, we may compare the slopes of the mean of 61 + 62 with that 

 of 63 -f 64. Here the t test 



Uh + 62) - 1(63 + 6.) ^ ^^^25 



VVar. Uh + 62) - K&3 + 64) 

 with a p value less than 0.001. 



