IX 



INTERCONNECTED CHAINS: PSYCHOPHYSICAL 



DISCRIMINATION 



In chapter iii we dealt with the general problem of the interac- 

 tions among interconnected parallel chains of neurons, and more es- 

 pecially with the mutual reduction of the a's developed by the simul- 

 taneously stimulated chains when the interconnections are inhibitory. 

 We also exhibited a mechanism capable of transmitting excitation 

 when the intensity of the stimulus lies on a limited range only. In 

 this chapter we shall apply these considerations to the interpreta- 

 tion of sequences of a stimulus and a response of a type often stud- 

 ied by psychologists, which we shall speak of as discriminal se- 

 quences. By a discriminal sequence we shall mean any sequence in 

 which the response is one of a limited set of qualitatively different 

 possible responses, while that feature of the stimulus that deter- 

 mines which response of the set is to occur is either its absolute in- 



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 56 



