134 John B. Calhoun 



escape the conclusion that during evolution a separate compensating 

 mechanism for each must have arisen. This means that there is a d', a v', 

 and an A', and that /jl' = id'v' / A'). Furthermore, when mm' = 1-0, [i = 

 \/\x. Having arrived at these insights, one is logically lead to ask: "What 

 do d\ v' , and A' most likely represent biologically?" Although answering 

 this ciuestion is not necessary for the general theoretical formulations, an 

 attempt to specify their more likely nature may be helpful in searching 

 for their identification. 



d' represents the degree to which the stimuli emanating from any con- 

 figuration pass unselectively from the sense organs into the memory store 

 of the central nervous system (CNS). Thus, an increase in d' means 

 facilitation of passage of stimuli into the CNS, while a decrease in d' indi- 

 cates impeding or preventing stimuli from getting to the CNS. When the 

 target diameter of associates increases through evolution by acquiring 

 more (/-genes, a compensating evolution of a d'-mechanism wall permit a 

 discrimination among the <i-genes such that in that brief span of time re- 

 quired for psychological contact only a portion of the c?-genes of the other 

 individual will be responded to. It must be kept clearly in mind that an in- 

 crease in the efficiency of the mechanism which serves to alter d' , decreases 

 d'. Such a decrease in d' imphes the evolution of a filtering device which re- 

 duces the amount of information about others per unit time arriving at 

 the sense organs, which is permitted to pass from them into the integrative 

 centers of the nervous system. Without specifying what CNS structure 

 serves the d' function, it meets the reciuirements hypothesized by Broad- 

 bent for his CNS "filter." See Section IX. 



v' also represents a process internal to the indi\'idual. It cannot have 

 any influence upon the motor component of v. Therefore it must affect 

 the consequences of those sensory capacities which enable the individual 

 to achieve a psychological contact prior to an actual physical one. This is 

 the r component of velocity mentioned in Section XIII, A, 1. Just as an 

 increase in r increases v by decreasing the time required for a contact, so 

 must a decrease in v' function to increase the time from the moment of 

 input of a signal from a d-gene at the sensory organ until this transformed 

 signal reaches and evokes a response at an effector. Thus v' could represent 

 either a structural or biochemical alteration in the time required for an 

 impulse to pass over a synapse, or it could be represented by an alteration 

 in the number of neurons in the circuit which will also alter transmission 

 time. But we must not confuse the magnitude of v' with the efficiency of 

 the mechanism involved. An increase in v' means a decrease in the efficiency 

 of the mechanism, that is increased synaptic transmission, while a decrease 

 in v' follows from an increase in the efficiency of the mechanism in impeding 

 the passage of the signal along the circuit between the sense organ to the 

 effectors. 



