Debunking the Seven-Plus-or-Minus-Two Myth

August 30, 2006 at 12:28 am 1 comment

Why are phone numbers seven digits? Because our short-term memory can only store 7 numbers at once.

I heard that first in grade school, and it seems to be one of those things that sticks in your head. It’s so obvious and sensible!

But is it really? So you never forget a phone number between being told the number, to writing it down?

– Zero is perfection. One is focus.
– Two is a bit. Three is the simplest complexity.
– Four is a square. Five is a handful.
– Six is … just after five.
– Seven is many. What’s seven? It’s not a particularly special small integer.

Doumont takes a closer look at the paper that started this all — Miller’s “The magical number seven, plus or minus two” in The Psychological Review.

What George Miller presented as “some limits on our capacity for processing information” [1, p.81] quickly turned into an acceptable average: Miller’s whole paper is now ignorantly summed up as “seven is OK”.

The truth is, Miller’s paper doesn’t really provide much evidence for 7 to be the magic number of our short-term memory.

First, the number seven plus or minus two is at best an ASYMPTOTICAL LIMIT,

In fact, the calculations in Miller’s paper to come up with 7 as the magic number is unclear. He does not claim this to be the case and the experiments come up with a limit between 4 and 10.

Narratively, Miller seems obsessed with the number 7, which undoubtebly biases his judgment. From his original paper,

What about the seven wonders of the world, the seven seas, the seven deadly sins, the seven daughters of Atlas in Pleiades, the seven ages of man, the seven levels of hell, …

But no where in the paper does he actually say 7 is the number of things we can process.

Doumont, J. (2002). Magical Numbers: The Seven-Plus-or-Minus-Two Myth. IEEE Transactions on Professional Communication, 45(2), 123-127.

Miller, G. A. (1956). The magical number seven, plus or minus two: Some limits on our capacity for processing information. The Psychological Review, 63(2), 81-97. [HTML]

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Entry filed under: Communication, Myth, Psychology, Seven.

When Can I Expect an Email Response? Does the Internet improve social relationships and psychological well-being?

1 Comment Add your own

  • 1. Teja  |  August 30, 2006 at 8:18 pm

    That’s weird, I was reading the Tipping Point this afteroon and I came across the same thing. It even mentioned the famous essay ‘the magical number seven’ (I think… was it the one conducted by a respectable fellow who worked at Bell?) which you mentioned.

    Reply

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