ABSTRACT
The Relation of Higher and Lower Levels. We have now to consider how the various higher and lower-level clearing-houses in the nervous system are related to one another. Instead, however, of starting with one particular stimulus and asking how it comes to arouse a particular response, we must begin, as psychologists, with the total situation in which the body finds itself. Of the innumerable impulses which are coming in from the greater number of our sense organs all the while, only a small proportion can ultimately reach the final common paths, the motor neurones which excite the muscles. But v^ry many which themselves play no final part have yet, at one level or another, a say in what finally shall take place; typically by barring out other impulses which otherwise would get through. And only a small proportion of these ultimately give rise to consciousness in the form of mediating the individual's awareness of some part of the situation. A process of selection takes place quite early in the afferent (incoming) course of the impulse. Further, a set of excitations which in themselves would each be unnoticed and have no central effects may, if they happen to come together in a certain pattern, get through and take effect at once; for example, a set of black and yellow streaks in the landscape when, and only when, coiled upon one another in the rattlesnake fashion, or a set of sounds in an otherwise unnoticed hubbub if they happen to be arranged in the pattern of our own name.
