Inherited Tendencies : Part 1

The Science of Human Nature: A Psychology For Beginners
by William Henry Pyle

(Page 4 of 15)

Stimulus and Response. We have learned something about the sense organs and their functions. We have seen that it is through the sense organs that the world affects us, stimulates us. And we have said that we are stimulated in order that we may respond.

We must now inquire into the nature of our responses. We are moving, active beings. But how do we move, how do we act when stimulated? Why do we do one thing rather than another? Why do we do one thing at one time and a different thing at another time?

Before we answer these questions it will be necessary for us to get a more definite and complete idea of the nature of stimulus and response. We have already used these terms, but we must now give a more definite account of them. It was said in the preceding chapter that when a muscle contracts, it must first receive a nerve-impulse. Now, anything which starts this nerve-impulse is called the stimulus. The muscular movement which follows is, of course, the response. The nervous system forms the connection between the stimulus and response.

The stimulus which brings about a response may be very simple. Or, on the other hand, it may be very complex. If one blows upon the eyelids of a baby, the lids automatically close. The blowing is the stimulus and the closing of the lids is the response. Both stimulus and response are here very simple.

But sometimes the stimulus is more complex, not merely the simple excitation of one sense organ, but a complicated stimulation of an organ, or the simultaneous stimulation of several organs. In playing ball, the stimulus for the batter is the on-coming ball. The response is the stroke. This case is much more complex than the reflex closing of the eyelids. The ball may be pitched in many different ways and the response changes with these variations.

In piano playing, the stimulus is the notes written in their particular places on the staff. Not only must the position of the notes on the staff be taken into account, but also many other things, such as sharps and flats, and various characters which give directions as to the manner in which the music is to be played. The striking of the notes in the proper order, in the proper time, and with the proper force, is the response.

In typewriting, the stimulus is the copy, or the idea of what is to be written, and the response is the striking of the keys in the proper order. Speaking generally, we may say that the stimulus is the force or forces which excite the sense organs, and thereby, through the nervous system, bring about a muscular response.

This is the ordinary type of action, but we have already indicated a different type. In speaking of typewriting we said the stimulus might be either the copy or ideas. One can write from copy or dictation, in which the stimulus is the written or spoken word, but one can also write as one thinks of what one wishes to write. The latter is known as centrally initiated action. That is to say, the stimulus comes from within, in the brain, rather than from without.

Let us explain this kind of stimulation a little further. Suppose I am sitting in my chair reading. I finish a chapter and look at my watch. I notice that it is three o'clock, and recall that I was to meet a friend at that time. The stimulus in this case is in the brain itself; it is the nervous activity which corresponds to the idea of meeting my friend. If we disregard the distinction between mind and body, we may say that the stimulus for a response may be an idea as well as a perception, the perception arising from the immediate stimulation of a sense organ, and the idea arising from an excitation of the brain not caused by an immediate stimulation of a sense organ.

Instincts and Habits. In human action it is evident that there is always a stimulus to start the nerve-impulse which causes the action. If we make inquiry concerning the connection between the stimulus and response; if we ask how it has come about that a particular stimulus causes a particular response rather than some other possible response, we find two kinds of causes. In one case the causal connection is established through heredity; in the other, the causal connection is established during a person's lifetime through training.

A chicken, for example, hides under some cover the first time it hears the cry of a hawk; it scratches the first time its feet touch sand or gravel; it pecks the first time it sees an insect near by. An infant closes its eyes the first time it feels cold wind blow upon them; it cries the first time it feels pain; it clasps its fingers together the first time a touch is felt inside them. The child's nervous system is so organized that, in each of the cases named, the stimulus brings forth the particular, definite response. These acts do not have to be learned.

But it is quite different in typewriting and piano playing. One must learn what keys on the piano to strike in response to the various situations of the notes as written in the music. One must also learn the keys on the typewriter before he can operate a typewriter. And in the case of other habits, we find, for example, that one does not respond by saying "81" for 9 times 9; nor "13" for 6 plus 7; nor "8" for 15 minus 7; nor "8" for the square root of 64; nor "144" for the square of 12, etc., until one has learned in each case.

Some connections between stimulus and response we have through inheritance; all others are built up and established in one's lifetime, particularly in the first thirty years of one's life.

We have spoken of bonds between stimulus and response, but have not explained just what can be meant by a bond. In what sense are stimulus and response bound together? A bond is a matter of greater permeability, of less resistance in one direction through the nervous system than in other directions. Nerves are conductors for nerve-currents. When a nerve-current is started in a sense organ, it passes on through the path of least resistance.

Copyright 1917 by Silver, Burdett & Company.