B-R into use. After
this has occurred a number of times, the linkage B-R has been so
strengthened by repeated exercise that it can operate alone, so that
the rabbit brings the shrinking response even in the absence of A, the
noise.

[Illustration: Fig. 55.--Attachment of the substitute stimulus in the
case of the conditioned reflex.]

At first, the child shrinks from the noise, but, the rabbit being
before his eyes, he incidentally shrinks from the rabbit as well. He
really shrinks in response to all the stimuli acting on him at that
moment. He shrinks from the whole situation. He makes a unitary
response to the whole collection of contiguous stimuli, and thus
exercises the linkage between each stimulus and their joint response.
The {403} linkage between rabbit and shrinking is later strong enough
to work alone. It is a clear case of the law of combination.

2. Learning the names of things.

A child who can imitate simple words that he hears is shown a penny
and the word "penny" is spoken to him. To this combination of stimuli
he responds by saying the word. This is primarily a response to the
auditory stimulus, since the sight of the penny, though it might
probably have aroused some response, and even some vocal response from
the child, had no strong linkage with this particular vocal response.
But the auditory stimulus determined the response, and attracted the
visual stimulus into this particular channel of saying "penny". The
linkage from the sight of the penny to the saying of this word being
thus strengthened by exercise, the seen penny later gives the right
vocal response, without any auditory stimulus to assist.

[Illustration: Fig. 56.--Linkage of a name to an object. The diagram
is arranged to illustrate the formation of a linkage from the sight
of the object to saying its name. A very similar diagram would
illustrate the linkage from the name to the thought or image of the
object. The acquiring of mental images seems to be essentially the
same process as the acquiring of conditioned reflexes, and of names.
(Figure text: object seen, various possible responses, name heard,
name spoken)]

{404}

B. Substitute Stimulus Originally an Essential Member Of A Team of
Stimuli That Aroused the Response

1. Observed grouping or relationship.

"Learning by observation" is a very important human accomplishment,
and we found many evidences of its importance in our study of the
process