Well, IQ tests given in the 1930's and 40's(?) had the results re-scaled today, and the average IQ was 70.
Note, that we're all trained today in taking IQ tests. E.g. one question asked "There are no Elephants in Germany. Munich is in Germany. How many Elephants are in Munich?" with possible answers of 0, 1, 2, 12.
Back then a layman might think "Munich is a big city; I bet there's one or two in the zoo there!" and answer 1 or 2. Because they didn't understand it was a logic question and there is an expectation when taking IQ tests that common sense is not being tested.
Note, that we're all trained today in taking IQ tests. E.g. one question asked "There are no Elephants in Germany. Munich is in Germany. How many Elephants are in Munich?" with possible answers of 0, 1, 2, 12.
Back then a layman might think "Munich is a big city; I bet there's one or two in the zoo there!" and answer 1 or 2. Because they didn't understand it was a logic question and there is an expectation when taking IQ tests that common sense is not being tested.