Numbers Don't Lie

Friday, March 10, 2006

The magical number 7

Back in the 1950s, a Harvard psychologist named George A. Miller wrote "The Magical number seven, plus or minus two," a landmark journal article. Miller studied short-term memory, especially the quick memorization of random sequences of numbers. He wanted to know, going into the study, how many numbers people could be reliably expected to remember a few minutes after having been told those numbers only once.
The answer - the magical number - was about 7. Some people able to remember 8 or 9 numbers and equal number of people able to remember only 5 or 6 numbers, so Miller figured that 7 (plus or minus 2) numbers accurately represented the ability range of nearly the entire population. That is why all local telephone numbers were designed as 7-digits.
Miller's concept went beyond numbers, though, to other organization of data. For example, most of us can remember about 7 recently learned pieces of similarly classified data, like names or clues in a parlor game. This is also explained the magic number 6 in my last post ( "Winner takes it all").
Source - Accidental Empires , Chapter 2.



Blogger Rochechanteuse said...

The study went on to say that it's not just numbers that get encoded in the 7 +/-2 study. When he had them "chunk" the information (i.e. instead of memorizing 4 7 2 5 2 1 6 9 2, they were memorized as "472" "521" "692"), they would remember 7 +/-2 CHUNKS. Hence the reason why phone numbers today are in 3 digits area code, and three digits followed by a dash and four more digits.

BTW, this only applies for short-term memory. Long term memory seems to be limitless.

- Roche

5:15 PM

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6:02 PM


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