The Magical Number Seven, Plus or Minus Two
Miller. 1956. (View Wikipedia →)
Miller proposed as a law of human cognition and information processing that humans can effectively process no more than seven units, or chunks, of information, plus or minus two pieces of information, at any given time. That limit applied to short-term memory and to a number of other cognitive processes, such as distinguishing different sound tones and perceiving objects at a glance.
Even if the science of 70 years ago isn’t perfect - the subject matter of this paper is becoming increasingly more relevant. The constraints of mobile phones and audio interfaces make information architecture increasingly important. I find ‘seven, plus or minus two’ to be a useful way to start a conversation about user journeys and information overload. Also - the title of this paper is one of the best examples of copywriting I can think of.