PSYCHOLOGY'S new conception of behavior and its relation to the central nervous system emphasizes the concepts of inhibition and selection. Our theories of the 1930 to 1940 period were infused with a philosophy that conceptualized organisms as passive recipients of experience rather than generators of behavior, and we took as our primary goal the task of explaining why an organism behaves. Neurophysiological discoveries have caused us to change our fundamental conception of the organism as passive recipient to actor, and now we ask why some responses are selected for expression and others are not. The question of inhibition has become central.
Inhibition has both biological and psychological referents. For example, beginning at 11 or 12 weeks of age many children fail to exhibit the Moro reflex, suggesting that the cerebral cortex has now begun to exert inhibitory control over the centers that mediate this reflex. At about the same time
Jerome Kagan. Biological Aspects of Inhibition Systems. Am J Dis Child. 1967;114(5):507–512. doi:10.1001/archpedi.1967.02090260095006