A habit of mine which some (ok, many!) find annoying is my skepticism. It's a "show me" attitude that apparently has been inherited by at least one son (RadRob). I think of it as just a healthy form of critical thinking, perhaps taken slightly to excess. But others are troubled to no end when they say that it's raining and I instinctively look out the window, instead of taking their word for it.
Nonetheless, I try to apply a heaping measure of disbelief to any claims, both ones which don't fit in with the rest of my experience, and ones toward which I'm prejudiced in favor. Alas, I don't always succeed. I was therefore heartened to spy a comment about Samuel Johnson's critical attitude, reported from an encounter on 7 May 1773 by James Boswell (emphasis added):
He did not give me full credit when I mentioned that I had carried on a short conversation by signs with some Esquimaux who were then in London, particularly with one of them who was a priest. He thought I could not make them understand me. No man was more incredulous as to particular facts, which were at all extraordinary; and therefore no man was more scrupulously inquisitive, in order to discover the truth.
Would that I could be so consistently healthy in my skeptical outlook ...