I invite readers to consider the model of persuasion in evidence here as the author contrasts two classes, one boring (focusing on captions and main ideas) and another exciting (focusing on mummies). The point being made (and how often have we seen this?) is that "cognitive scientists have known for decades that the most important factor in comprehension isn’t a set of generally applicable skills; it’s how much background knowledge the reader has about the topic." Well. They say this; I wouldn't exactly say they know it. And that's because, first, you don't know any reading without abstract knowledge. And second, it doesn't really matter what content knowledge is being taught - mummies, sharks, the New York Islanders, whatever floats their boat. Because the content is (and has always been) the McGuffin.