I think some people are especially good at taking standardized test, just as some people are inexplicably bad at it. My DD shows a natural facility for anything multiple-choice. Her math HW sometimes has some multiple-choice and she tends to cross out the obviously dumb answers and pick one of the best two based on hunch. At least, I think this is what she does; she's good at working problems in her head, but not so good that she could do some of these without any writing. Also, she'll admit she didn't work the problem. "This one looked right." (She's often correct, but not always.) Her father is also an exceptionally good standardized test taker. I'm pretty good, too.
I have two siblings whom I'd assess as fairly similar in intelligence. One is a good test taker and the other is not, alwasy underperforming his apparent ability. Perhaps not coincidentally, the one is good is highly confident and relaxed in daily life; the other is more anxious and more of a second-guesser.
