A psych professor claimed, years ago, that the number is actually 5 +/- 2, but I can't remember his argument. Something about including error of measurement fr

A psych professor claimed, years ago, that the number is actually 5 +/- 2, but I can't remember his argument. Something about including error of measurement from the experiments, maybe? Regardless, he said it is why 7 phone # digits is often difficult for some people, because it is on the high end of what most people can remember.