The Magic Nmber Seven Plus or Minus Two

Working through the 23 Things, I was reminded of George Miller's 1957 seminal research into the nature of working memory: The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information by George A. Miller (1956) of Harvard University. First published in Psychological Review, 63, 81-97. You can find a complete full-text copy posted at http://psychclassics.yorku.ca/Miller/. I'll talk later about the wonderful things you can find posted at http://psychclassics.yorku.ca/, but now I want to talk a little about Miller's amazing discovery and its contribution to information theory. Dr. Miller was doing important grant research work for the U.S. Navy during and after the Korean War to learn how many bits of information a navy signalman could remember while transmitting or receiving coded signals. Though this was in the days before the digital revolution, Miller's research has played a crucial role in the theory and development of digital communication (as well as all communication and memory, human or machine). In essence, Miller's discovery is this: the human brain can retain in working memory only 7 bits of information (yes or no, on or off) give or take two additional bits of information. We suffer from information overload whenever we try to absorb more than 7 (+/- 2) bits of information unless we chunk this information into recognizable groups. An excellent example of chunking is telephone numbers: we can remember the 7 numbers in a phone number easily enough, but when we add the numbers of the area code we go immediately into information overload unless we chunk those numbers and piece the chunks together. Remembering 815 or 315 as one chunked bit rather than 3 separate bits is relatively easy. So, to dial long distance, you remember 1 plus area code plus phone number plus extension. Each one of these elements can be chunked and then pieced together, up to 7 +/-2 chunks. If we try to remember each number separately and in serial order, it seems extremely difficult because we are trying to remember more than seven (plus or minus two) pieces of information, and the cognitive load is tremendous. But if we remember separate chunks and piece them together, we can easily recall the entire number. Long term memory is similarly created out of "chunks" that are pieced together in recall.

Tackling the 23 Things is easy when you take each thing one at a time. But all 23 together can seem like an insurmountable ordeal....