A cursory look around the Internet doesn’t turn up any articles about sound-effect words and learning to read. (This doesn’t mean they aren’t out there; it just means I don’t know where to look!) But, in any case, 1) my seven-year-old particularly enjoys reading the made-up “sound-effect words,” and 2) he can’t really “guess” at the word from the context, but needs to look at the letters and decode.
So it triggers—I think—a slightly different sort of reading than the rest of the text.
Comic books, of course, often work in similar ways, with a number of fun made-up words to create various sound effects.
The “سلسلة السمكة الذهبية” often features sound-effect words, perhaps intentionally. All also have a very enticing flap at the end.
And, if we can get some of this $70 billion back from our former president, then we could buy this series—and more—for every public-school library in Egypt….