1. The Social Use of Space 177 



If rats are maintained in isolation for several weeks or months and then 

 placed in an emotional activity alley, a large proportion of them never 

 go out into the alley from the "home" compartment. From this I infer that 

 there is some upper threshold, Th, of DMA which "overloads" that neural 

 circuit permitting its expression. The three dots in sketch (2) denote such 

 overbadings. In any sample of subjects, most of whom avoid entering the 

 alley, there are a few with various lengthened latencies, causing delays of 

 up to nearly the end of the 2-hour test period before initiation of the initial 

 phase of intense hyperactivity. From this fact it is apparent that the normal 

 DMA becomes replaced by some generalized stress state, GSS, which 

 follows a similar (but lower?) rate of decline than the DMA. GSS lacks a 

 striated muscle component. Once it has dechned to Th, GSS becomes 

 transformed to DMA. Such subjects, owing to their having been protected 

 from impinging external stimuli for such a long time during their isolation, 

 view the alley configuration as an increased intensity, E. An inference from 

 this is that there is a slow drift downward of Th toward 6 during the weeks 

 of isolation when opportunities for adjustments Ai • • • An in response to 

 El • ' • to En are absent. Thus, depending upon how extensive this drift 

 has been, any particular E, such as represented by the activity alley, raises 

 the GSS different amounts above Th. I suspect, though my data are not 

 conclusive, that the more elevated GSS is above Th the lower will be its 

 rate of decline. These differences are diagrammatically shown in sketch 

 (2) of Fig. 41. Given sufficient time with no interference by other E's, 

 DMA will eventually reach h and an adjustment, A, transpires. 



Now we may consider the more normal coiu-se of maturation, experience 

 with a sequence of ^i • • • En [sketch (3) in Fig. 41]. One general observa- 

 tion first. The greater has been the experience of rats in the sense of a larger 

 number of different E's to which adjustments, A, have been made, the 

 lower will be the probability of withdrawal in the form of failing to enter 

 the alley from the starting "home" compartment. An explicit experiment 

 concerning this point has already been cited with reference to Table lb. 

 Such results indicate an elevation of Th to Tha following each A, and this 

 elevation will be proportional to the magnitude of E provided E does not 

 elicit a DMA exceeding Th. Thus, at some later time an intense E, desig- 

 nated as 2Ei in sketch (3), will result in adjustment Ai, although had a 

 2E configuration occurred earlier it would have resulted in the undesirable 

 consequences accompanying elevation of DMA above Th. There is another 

 conclusion, somewhat more tentative, though some of my results do sup- 

 port it. This is that with each successive E, the rate of decline of DMA 

 increases. In other words, the aap refractory period decreases. Thus, the 

 more adjustments an individual makes, the better he will be al)le to curtail 

 oif„p = df. I have already mentioned the failure of a second exposure to a 



