Here is the definition given by the book/survey tool (emphasis mine):
You like to think. You like mental activity. You like exercising the “muscles” of your brain, stretching them in multiple directions. This need for mental activity may be focused; for example, you may be trying to solve a problem or develop an idea or understand
another person’s feelings your horse. The exact focus will depend on your other strengths. On the other hand, this mental activity may very well lack focus. The theme of Intellection does not dictate what you are thinking about; it simply describes that you like to think. You are the kind of person who enjoys your time alone because it is your time for musing and reflection. You are introspective. In a sense you are your own best companion, as you pose yourself questions and try out answers (is he off or unbalanced? if I half halt in a corner, does he rebalance? ) on yourself to see how they sound. This introspection may (often) lead you to a slight sense of discontent as you compare what you are actually doing with all the thoughts and ideas that your mind conceives. Or this introspection may tend toward more pragmatic matters such as the events of the day or a conversation that you plan to have later. Wherever it leads you, this mental hum is one of the constants of your life.
Poor Jackson. I'm constantly thinking of new patterns to ride, new turn out schedules, and I analyze each ride to death before, during and after. These pictures are from a lesson this past January.