Conclusion
The Central Idea is that pleasure in the mind results
when two ideas come together with a neat match or neat fit, and that much of
a day's pleasure comes from this source. The Tree has shown forty examples and I
hope you agree about at least a few. But suppose this is so, and they are indeed
all a consequence of one single mechanism or process in the brain: is that
important, does it matter?
One route toward an answer is to think about "quality time". How does that differ from nondescript time or wasted time? But on this page, we take a different route and take up a famous question: Isn't there something more to life than eating, shopping and sexual concerns? --- aren't there "higher things"?
I will affirm Yes; I don't know what they are, but the Tree of Treats is a step toward finding out.
Even at a lower level, the Tree makes a point. Eating, shopping and sex are well covered on television; by contrast, pleasure in one's mind is not as easy to portray but is just as important --- it pops up everywhere. The many separate mental treats that people have been reporting for centuries all seem to come from one source inside the brain. Not to understand this source is not to understand oneself, it is like going through life with one eye shut. To understand it, turn off the commercials! --- and get to know what kinds of good match or good fit give you a treat.
( Concern for other people: even
if this is big for you, you still need to look 
inside yourself, to learn about the system. Everyone has the same basic brain/pleasure system
even if yours is more alert to what you see and mine to what I hear, or mine to the
trees and sky and yours more to the people you meet. Though we may get it in different amounts by different
ways, we all get the same
treat, so you can learn about other people by looking inside yourself. Click for
more on this topic.)
Higher Things?
I favor a comparison with music. The most basic pleasure is that of rhythm; then there are the mid-level pleasures of melody and of an expected note coming just as it should; and then there is the high pleasure that results from the whole of a work -- its different passages adding and combining to yield an effect that is more than the effect of the separate passages on their own.
This is a sequence from what is simpler to what is more mysterious; even if we understood the bottom layers, that would not account for the top. But surely it is a step on the way, isn't it? The more we understand about the simpler parts, the more clearly we see how the top joins on.
So it is with other intimations in the mind. Beside great music, there are the clear night sky and the thunder of the surf, the noble public speech and the saintly private action. About these, what do we feel and why do we feel it? I have no more Ultimate Answers than anyone else, but understanding the mid-level sensations on the Tree of Treats is surely a step on the way, don't you think?
Please remember, comments are welcome! --- each of us needs all the help we can get.