The problem with Miller’s work is that later research has proved him wrong. In 2001, Nelson Cowan of the University of Missouri wondered whether that magic rule of seven was really true and conducted a wide survey of all the new research on the topic. It turns out that the number of items one can retain in short-term memory isn’t seven. It’s four.9 People often think that they can memorize more than that, using a mnemonic device or by just concentrating harder. But the research is fairly clear that we can only remember four “chunks” of data.
