I sometimes see horses in a
pasture eating clover. So, as far as this last experience is concerned,
when I think "horse" I should also think "clover." I sometimes see a
horse running when a train whistles, so "whistle" and "horse" should be
coupled in my mind. A horse once kicked me on the shoulder, so "horse"
and "shoulder" should be connected in my mind. And so they are. The very
fact that these various experiences come back to me proves that they are
connected in my mind in accordance with the original experiences. The
revival of various horse experiences has come to me faster than I could
write them down, and they are all bound together in my memory. If I
should write them all out, it would take many hours, perhaps days.

Not only are these "horse ideas" bound together with one another, but
they are bound more or less directly, more or less closely, to
everything else in my life. I can, therefore, pass in thought from the
idea "horse" to any other idea, directly or indirectly. Now, in any
given case, what idea will actually come first after I have the idea
"horse"? This depends upon the tendencies established in the nervous
system. The brain process underlying the idea "horse" has connections
with many other processes and tends to excite these processes. The
factors that strengthen these tendencies or connections are the
frequency, recency, primacy, and vividness of experience. Let us
consider, in some detail, each of these factors.

=Primacy of Experience.= A strong factor in determining association is the
_first experience_. The first, the original, coupling of ideas tends to
persist. The first connection is nearly always a strong one, and is also
strengthened by frequent repetition in memory. Our first experience with
people and things persists with great strength, across the years, in
spite of other associations and connections established later. Just now
there comes to mind my first experience with a certain famous scientist.
It was many years ago. I was a student in an eastern university. This
man gave a public lecture at the opening of the session. I remember many
details of the occurrence with great vividness. Although I studied under
this man for three years, no other experience with him is more prominent
than the first. First experiences give rise to such strong connections
between ideas that these connections often persist and hold their own as
against other connections depending upon other factors.

T