The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information – 7 +/- 2 bits of information
Based on cognitive psychologist, George Miller’s research at Harvard
If you were given a series of letters to remember (e.g., twpbdrt), your ability to remember the series correctly would probably depend on the number of letters in the series. Most people can remember a series of letters correctly if there are only 3 or 5 letters in the series. About half the people asked to remember a seven-letter series have difficulty. Relatively few people can remember series consisting of 9 or 11 letters correctly. This finding, that the limit on short term memory is around 7 items, is one of the most consistent findings in all of psychology. George Miller, a very famous cognitive psychologist, coined the phrase “the magical number seven, plus or minus two,” to describe the capacity of working memory.
There is a clear and definite limit to our ability to identify information beyond a certain number of stimuli. He called it the “span of absolute judgment,” in that the level of accuracy of one’s ability to recall specific information begins to fall off after having reached critical overload in short term memory. Miller proposes that the limit is approximately seven bits of information, give or take one or two.
The span of absolute judgment and the span of immediate memory impose severe limitations on the amount of information that we are able to receive, process, and remember. By organizing the stimulus input simultaneously into several dimensions and successively into a sequence or chunks, we manage to break (or at least stretch) this informational bottleneck.
We can increase the absolute capacity of short term memory by combining bits of information into meaningful units, or chunks. This process is called “chunking.” Effective communicators try to help you chunk information by focusing on the ways that the pieces of information to be learned relate to one another. To make your presentations more effective, practice “chunking” and try not to work with more than seven chunks at a time.
It’s not that we can only remember seven things, it’s more that we can only (barely) process seven random things. Since there is no effective way to simply cram thirteen bits of information into a short-term memory system that can only handle seven plus or minus two, we need a method which will reduce the number of bits of information down to a number short term memory can handle.
Fortunately, such a method exists. This method is called “chunking”. To make chunking work, you need to recognize that some bits of information can be grouped together in a logical and repeatable way. We call such a group of bits a “chunk”.
Use a structure and follow it.
And finally, what about the magical number seven? What about the seven wonders of the world, the seven seas, the seven deadly sins, the seven daughters of Atlas in the Pleiades, the seven ages of man, the seven levels of hell, the seven primary colors, the seven notes of the musical scale, and the seven days of the week? What about the seven-point rating scale, the seven categories for absolute judgment, the seven objects in the span of attention, and the seven digits in the span of immediate memory? Perhaps there is something deep and profound behind all these sevens, something just calling out for us to discover it. But I suspect that it is only a pernicious, Pythagorean coincidence.
