Your short-term memory holds about seven items — and that number isn't a coincidence

In 1956, psychologist George Miller reviewed decades of experiments and found a strange coincidence: whether people were recalling digits, judging pitches, or naming colors, performance reliably broke down past about seven items, plus or minus two. Miller's paper became one of the most cited in psychology, and gave 'chunking' — grouping information to beat the limit — its name.

— George A. Miller, The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information — Psychological Review, 1956