My experience growing up was that I had personality traits that were strong since birth (and still are today), and every other traits that I developed as I aged and experienced life.

In these growing years, the people I looked up to, the artists I liked and any other person that had something interesting to me all had an effect on my personality because I replicated the things I liked about these people.

So reading the green text, he probably did the same thing with Jerry and it became a part of his personality.