[WS:] Good point - this caught my attention too. Or more specifically, people considered "intelligent" based on a standardized test of intelligence seem to be more prone to be fooled by a relatively simple puzzle.
My conjecture is that this has something to do with the way those tests works. When I was preparing for GRE I was told that trying to actually solve each problem is a bad strategy, because there is not enough time to do this. In fact, these tests are designed that way so you cannot score high by applying critical reasoning, because speed counts more than critical thinking ability. Consequently, you must use mental "shortcuts" to solve these test problems quickly - shortcuts that the test preparation business will teach you for a fee.
The puzzles mentioned in the piece fool this shortcut taking that the so-called intelligent people are taught to take to look smart on tests, rather than critical thinking ability. If you posed the bat and ball problem as the simple equation 1.1 = ball + (1+ball) and solved it for ball you would get the answer right, but so would a sixth grader. But if you were trained not to rely on problem solving, which takes time, but instead on using shortcuts for speed, they got you by the balls so to speak.
So the title of the piece should read instead "Why do people who look smart on intelligence tests are so easily duped by puzzles that a sixth grader can solve?" And the answer to this question is "because they've been bamboozled by those tests that are inherently stupid."
-- Wojtek
"An anarchist is a neoliberal without money."