brain centers, as is the case with habit. The association of ideas,
which is the basis of their recall, is purely a matter of habit
formation.

When I think of George Washington, I also think of the Revolution, of
the government, of the presidency, of John Adams, Thomas Jefferson,
etc., because of the connections which these ideas have had in my mind
many times before. There is a basis in the brain structure for these
connections. There is nothing in any _idea_ that connects it with
another idea. Ideas become connected because of the _way in which we
experience them_, and the reason one idea calls up another idea is
because the brain process that is the cause of one idea brings about
another brain process that is the cause of a second idea. The whole
thing is merely a matter of the way the brain activities become
organized. Therefore the various laws of habit-formation have
application to memory in so far as memory is a matter of the association
of ideas, based on brain processes.

One often has the experience of trying to recall a name or a fact and
finds that he cannot. Presently the name or fact may come, or it may not
come till the next day or the next week. What is the cause of this
peculiar phenomenon? The explanation is to be found in the nervous
system. When one tries to recall the name and it will not come to mind,
there is some temporary block or hindrance in the nerve-path that leads
from one center to the other and one cannot think of the name till the
obstruction is removed. We go on thinking about other things, and in the
meantime the activities going on in the brain remove the obstruction; so
when the matter comes up again, the nerve current shoots through, and
behold, the name comes to mind.

[Illustration: FIGURE IV--ASSOCIATIVE CONNECTIONS
The diagram represents schematically the neural basis of the association
of ideas.]

Now the only preventive of such an occurrence is to be found in the law
of habit, for the block ordinarily occurs in case of paths or bonds not
well established. We must _think together_ the things we wish to have
associated. Repetition is the key to the situation, repetition which is
the significant thing in habit-formation, repetition which is the only
way of coupling two things which we wish to have associated together.

Of course, there is no absolute coupling of two ideas. One sometimes
forgets his own name. When we are tired or ill, things which were the
most closely ass