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. The practical consequences of this factor in teaching are, of course, evident. Both teachers and parents should take great care in the matter of the first experiences of children. If the idea-connections of first experiences are likely to persist, then these connections should be desirable ones. They should not be useless connections, nor should they, ordinarily, be connections that will have to be radically undone later. Usually it is not economical to build up connections between ideas that will not serve permanently, except in cases in which the immaturity of the mind makes such a procedure necessary.