MagicNumberSeven-Miller(1956) - From:...

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From: [ Classics Editor's Note: Footnotes are in square brackets; references in round brackets ] The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information [ 1 ] George A. Miller (1956) Harvard University First published in Psychological Review , 63 , 81-97. My problem is that I have been persecuted by an integer. For seven years this number has followed me around, has intruded in my most private data, and has assaulted me from the pages of our most public journals. This number assumes a variety of disguises, being sometimes a little larger and sometimes a little smaller than usual, but never changing so much as to be unrecognizable. The persistence with which this number plagues me is far more than a random accident. There is, to quote a famous senator, a design behind it, some pattern governing its appearances. Either there really is something unusual about the number or else I am suffering from delusions of persecution. I shall begin my case history by telling you about some experiments that tested how accurately people can assign numbers to the magnitudes of various aspects of a stimulus. In the traditional language of psychology these would be called experiments in absolute judgment. Historical accident, however, has decreed that they should have another name. We now call them experiments on the capacity of people to transmit information. Since these experiments would not have been done without the appearance of information theory on the psychological scene, and since the results are analyzed in terms of the concepts of information theory, I shall have to preface my discussion with a few remarks about this theory. Information Measurement The "amount of information" is exactly the same concept that we have talked about for years under the name of "variance." The equations are different, but if we hold tight to the idea that anything that increases the variance also increases the amount of information we cannot go far astray. The advantages of this new way of talking about variance are simple enough. Variance is always stated in terms of the unit of measurement - inches, pounds, volts, etc. - whereas the amount of information is a dimensionless quantity. Since the information in a discrete statistical distribution does not depend upon the unit of measurement, we can extend the concept to situations where we have no metric and we would not ordinarily think of using [p. 82] the variance. And it also enables us to compare results obtained in quite different experimental situations where it would be meaningless to compare variances based on different metrics. So there are some good reasons for adopting the newer concept. The similarity of variance and amount of information might be explained this way: When we have a
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MagicNumberSeven-Miller(1956) - From:...

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