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 speakin