This might sound a bit crazy but do you guys talk online much? There are a bunch of online quizzes friends and I procastinate with by linking to each other, if you were say joking around with him linking quizzes, and eventually bought up an AS test, he might see all his characteristics summed up. It's how I got some of my more introverted friends to take it to see if maybe it's just something we're all similar in, but they all scored heavily NT so somehow those quizzes are doing something right. (from my experience with them)