The Science of Human Nature: A Psychology for Beginners

by William Henry Pyle

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.

Now, some nerves are so organized and connected through inheritance as to offer small resistance. This forms a ready-made connection between stimulus and response. Muscular responses that are connected with their stimuli through inherited bonds, by inherited nerve structure, are called instincts. Those that are connected by acquired bonds are called habits. Sucking, crying, laughing, are instinctive acts. Adding, typewriting, piano playing, are habits.

The term instinct may be given to the act depending upon inherited structure, an inherited bond, or it may be given to the inherited bond itself. Similarly, the term habit may be given to an act that we have had to learn or to the bond which we ourselves establish between response and stimulus. In this book we shall usually mean by instinct an action depending upon inherited structure and by habit an act depending upon a bond established during lifetime. A good part of our early lives is spent in building up bonds between stimuli and responses. This establishing of bonds or connections is called learning.

Appearance of Inherited Tendencies. Not all of our inherited tendencies are manifested immediately after birth, nor indeed in the earliest years of childhood, but appear at different stages of the child’s growth. It has already been said that a child, soon after birth, will close its eyelids when they are blown upon. The lids do not close at this time if one strikes at them, but they will do this later. The proper working of an instinct or an inherited tendency, then, depends upon the child’s having reached a certain state of development.

The maturing of an instinct depends upon both age and use, that is to say, upon the age of the animal and the amount of use or exercise that the instinctive activity has had. The most important factor, however, seems to be age. While our knowledge of the dependence of an instinct upon the age of the animal is not quite so definite in the case of human instincts, the matter has been worked out in the case of chickens.