The most famous example was of black kids who never seen a ruby in their lives in the 50s. But Ruby the name was quite popular. So they got that question wrong. But it is normally used to denigrate Africans who have even less exposure to European norms than African Americans. Despite the genetic diversity of Africans being a lot higher than Europeans, they are often thrown into the same batch of "IQ deficient" groups. None of this is actually scientifically sound.