In 1956, the renowned cognitive psychologist George Miller published one of the field’s most widely cited papers, “The Magical Number Seven, Plus or Minus Two.” In it, he argued that although the brain can store a whole lifetime of knowledge in its trillions of connections, the number of items that humans can actively hold in their conscious awareness at once is limited, on average, to seven.
Those items might be a series of digits, a handful of objects scattered around a room, words in a list, or overlapping sounds. Whatever they are, Miller wrote, only seven of them can fit in what’s called working memory, where they are available for our focused attention and other cognitive processes. Their retention in working memory is short-lived and bounded: When they’re no longer actively being thought about, they’re stored elsewhere or forgotten.
Since Miller’s time, neuroscientists and psychologists have continued to study working memory and its surprisingly strict limitations. They have found that the limit may really be closer to four or five items than seven. And they have studied the ways in which people work around this constraint: We can remember all the digits of a phone number by “chunking” digits (remembering 1, then 4, as the single item 14, for instance), or develop mnemonic devices for shuffling random digits of pi out of longer-term storage.
But the explanation for why working memory starts to falter at such a seemingly low threshold has been elusive. Scientists can see that any attempt to exceed that limit causes the information to degrade: Neuronal representations get “thinner,” brain rhythms change and memories break down. This seems to occur with an even smaller number of items in patients who have been diagnosed with neurological disorders, such as schizophrenia.
The mechanism causing these failures, however, has remained unknown until recently.
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