Off-topic: Magic Number 7 (WAS: Re: XML Editors - Word 2000?? )

Andy.Bradbury at Andy.Bradbury at
Fri Jul 2 14:54:08 BST 1999

John Simpson wrote:

When I was at AT&T years ago, there was a company legend (possibly
apocryphal) about the length of US telephone numbers. According to this
legend, Bell Labs had surveyed large numbers of customers and determined
that, on average, people could remember 7 "things," plus or minus 3, about
another "thing." Ergo, a phone number would optimally be made up of: a
4-digit "main portion," sans exchange and area code; a 3-digit exchange;
and a 3-digit area code. This was supposedly in descending order of need to
remember the additional portions, assuming that you'd need primarily to
call people in your own exchange, followed by people in your area code but
outside your exchange, followed by people in other area codes.

I don't know where Rick's magic 7 comes from.

Small correction - it was 7+/- 2 "bits" of information, according to an
article by George A Miller in the Psychological Review, No. 63 (1956).
The article was called:  "The magical number seven, plus or minus two: some
limits on out capacity for processing information."

Whether AT&T did the research John mentions I wouldn't know


Andy B.

xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev at
Archived as: and on CD-ROM/ISBN 981-02-3594-1
To (un)subscribe, mailto:majordomo at the following message;
(un)subscribe xml-dev
To subscribe to the digests, mailto:majordomo at the following message;
subscribe xml-dev-digest
List coordinator, Henry Rzepa (mailto:rzepa at

More information about the Xml-dev mailing list