As folks became better-read and educated they began to understand that IQ test questions were a sort of puzzle, not a real honest question. The answer was expected to solve the puzzle, not be right in any way.
E.g. There are no Elephants in Germany. Munich is in Germany. How many elephants are there in Munich? A) 0 B) 1 C)2
Folks back then might answer B or C, because they figure hey there's probably a zoo in Munich, bet they have an elephant or two there. And be marked wrong.