Doesn't seem like too much of a study to me. From the article, I suppose they measured by how many people said they were somewhere above "never heard of it" on "proper numbers", "subjunctive scaling", and "declarative fractions". "Subjunctive scaling" and "declarative fractions" make no sense whatsoever. However, "proper numbers" could have an interpreted meaning even if it isn't an actual math topic. Some people could have said they have knowledge of "proper numbers" understanding it to mean something, so that wouldn't be a pure BS answer.
Also look at the findings. In the USA, women are .13 standard deviations below the average and men are .13 standard deviations above the average. That isn't much. The bottom 25% economically are .09 standard deviations below average and the top 25% are .11 standard deviations above average. Once again, not much difference.
Also, for economic class I would assume that the bottom 25% are less educated and probably answered "never heard of it" to more than just the three fake math topics. One of the three topics having a meaning that could be interpreted and economic class having a built in bias regarding the answers in my opinion throws a lot of doubt on the validity of the study.
