J. The Social Use of Space 135 



A word is required to differentiate clearly d' from v'. d' governs the prol)- 

 ability of a signal relating to c?-genes getting through the Broadbent typo 

 hypothesized "filter," while v' applies to the speed of transmission from the 

 filter to effectors. 



In a similar fashion, conceptualization of A' must be in terms of counter- 

 acting A. Where an A''^ group is living under optimum conditions, A may 

 be considered to be equal to 1.0. Optimum conditions will continue even 

 though A changes in so long as A A' = 1.0. For the sake of simplicity we 

 are considering the case where the only change in the system pertains to 

 A. Recall that A represents the area which the group shares. In essence 

 then A alters the time between contacts. Therefore A' must operate in a 

 similar but opposite direction to .4. Suppose that A increases. In effect 

 this is equivalent to a decrease in density. Under such circumstances there 

 can be no internal mechanism enhancing the probability of an actual 

 contact. Therefore, when A increases, an A' compensating mechanism in- 

 volves an imagined contact. To the extent that such an imagined contact 

 leads to an equal a refractory period, an A' mechanism will be effective. 

 Since an increase in A implies a decrease in A', a decrease in A' means an 

 increase in the capacity to store memories of associates, which can com- 

 pensate for their absence. Such an increased storage of memories implies 

 an increase in cortical mass. 



On the other hand, suppose that A decreases. This will reduce the time 

 elapsing between contacts, and since this will have the same consequence 

 as increasing N w^hen we are concerned with an Nh group, its members 

 will experience an increased da and an increase in 6/ above the optimum 

 level. In this situation A' must function to increase the relative time be- 

 tween contacts. The only way for this to happen is for the intensity, i, of 

 interaction to decrease. Recall that intensity of interaction has been 

 measured in terms of its duration, and that i = (a)^ when a represented 

 the duration of the refractory period following interaction. Furthermore, 

 Eq. (60) becomes: 



fJLfx'iN - 1) 



when we consider the several factors in the general sense where a variation 

 in one may influence any other. 

 Then 



an' = ^- (103) 



^ fxiN - 1) 



The reason for stating the equation in this fashion is that n' cannot alter 

 /i as such but can only alter its effects through changing something else. 



