“The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information” is a highly cited paper in psychology. It is often interpreted to argue that the number of objects an average human can hold in short-term memory is 7 ± 2. This has occasionally been referred to as Miller’s law.

The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information (PDF)