“The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information” is a 1956 paper by George A. Miller, published in Psychological Review (volume 63, pages 81 to 97) and first delivered as an invited address to the Eastern Psychological Association in April 1955. The full text is archived at the Classics in the History of Psychology collection.
Miller examined two separate questions and found that both pointed at the number seven. The first was the span of absolute judgment: when people are asked to sort a single varying stimulus - a tone of a given pitch, a line of a given length - into categories, they can reliably distinguish only about seven before they start making mistakes. Expressed in Shannon’s information units, this is roughly 2.6 bits. The second was the span of immediate memory: people can hold about seven items in mind at once. Crucially, Miller showed that the memory span is set by the number of items, or “chunks,” not by how much information each chunk carries - so grouping material into larger meaningful units lets people remember far more raw detail.
The paper’s lasting importance is less the specific number than the method. By measuring human performance in bits, Miller treated the mind as a channel with a fixed capacity, importing the mathematics of information theory into psychology. The “chunking” idea in particular reshaped how researchers thought about memory and learning, and it later informed how interfaces, phone numbers, and instructional material are designed.
The paper is one of the founding documents of the cognitive revolution that displaced behaviorism, and it is among the most cited papers in the history of psychology.