Your core personality is probably Enneagram Type 5, the THINKER, also known as the INTELLECTUAL or the NERD.
You are so logical and analytical that your guts are all dried out. Your expertise can't hide the fact that you're afraid to plunge into the real world. You fundamentally abhor ambiguity or complexity. The more perceptive and observant you are, the more often you feel the paranoia of your own shortcomings, particularly toward other people.
Your SECRET JOYS include doing math or crossword problems in your head, teaching children how to multiply, determining experimentally the exact best heat setting on your toaster, keeping careful track of expenses and gas mileage, and reading the columns of Marilyn vos Savant.
Some of your SECRET FEARS are that you will lose a treasured tool, that you'll mispronounce a common technical term, that you'll get ripped off by a common tradesman, or that you will blunder away your Queen for a Knight and two Pawns.
Under STRESS you begin to move toward Enneagram Type 7, the ENTHUSIAST. You become so desperate to appear smarter than everyone else that you seek to become an expert in all things, driving you either into ironic deconstructionist bullshit or into a chronically argumentative but platitudinous approach to every topic that you happen to talk about.
AT YOUR BEST you begin to move toward Enneagram Type 8, the LEADER. You expiate on topics with such boundless and pointless erudition that you appear once or twice on public broadcasting, purchase environmentally friendly products far in advance of your neighbors, and develop a politically correct speaking style hung on nothing but abstract nouns and passive verbs.
Source: Handprint : Enneagram 5