I read the same study, but it went even deeper. The study also took into account languages and their effect on behavior. The primary languages of the dark continent do not include gradation. The languages of Africa are only able to account for one, or many as far as grouping of like items. There is no way to measure or relate that the fruit is halfway up the tree, only that it is up. Because their native languages do not include the necessary words for gradation, the population cannot embrace or fully utilize abstract thought patterns necessary for mathematics. Because the same word exists for love and sex, rape equates with love. This creates a moral disconnect as well.
It's a very interesting read, if it can be sauced. I read the article several years ago on Tavistock run GLP clown breeding ground before waking up enough to make the switch.