SUMMARY OF CORTICAL EVOLUTION 263 



cases simply the "drainage" phenomenon to which 

 reference has just been made and in other cases this 

 effect supplemented by positive activation of two 

 antagonistic motor mechanisms so that their inter- 

 ference blocks all reactions of non-adaptive sorts. 



Whatever may be the unknown mechanism of 

 inhibition, the cortex of higher mammals certainly 

 does exercise repressive as well as activating influ- 

 ences upon more elementary components of behavior. 



In situations where the simpler immediate reflex 

 responses to stimuli fail to give satisfaction, resulting 

 in either interference and stasis within the lower 

 reflex centers or futile random movements, the excita- 

 tions overflow into the cortex. The immediate efl"ect 

 of cortical activity is inhibition of the lower non- 

 adaptive movements. A man "stops to think"; an ape 

 similarly pauses in a waiting attitude until he "sees 

 through" to a possible indirect way to reach the ob- 

 jective (Kohler). These inhibitory functions of the 

 cortex play a major role in all those human traits that 

 are described as self-control, "poise," and delibera- 

 tion. 



10. But inhibition is at the most only a first step 

 in cortical function. The positive contribution to be- 

 havior made by the cortex of higher mammals is evi- 

 dently recombination of the lower reflex units in pat- 

 terns determined not only by the stimulus complex 

 now acting but also by knitting into this complex the 

 relevant personally acquired mnemonic vestiges of 



