The Fanciful Number 2.9013, Plus or Minus Nothing

Ig Nobel Prize (psychology, 2012) winner Rolf Zwaan writes, in his blog, about the vaunted — yet uncertain — value of a particular number:

The Fanciful Number 2.9013, Plus or Minus Nothing
 Can we capture any aspect of human psychology in a single number?


In 1956 a paper entitled The Magical Number Seven Plus or Minus Two saw the light. It was destined to become a classic in cognitive psychology. In it, George A. Miller argued that human short-term memory is limited to seven units of information. The 7 was just an approximation, which is why Miller added the cautious plus-or-minus-two…. Miller’s proposal is modest…. not claimed to be exact [, and] derived in a straightforward way from the data.

There is another number in psychology that makes a lot less sense: the number 2.9013. It represents the ratio between positive emotions and negative emotions that an individual or a group expresses within a given period of time. How did this number get to be so exact, with no less than four decimals? I mean it’s not 3 plus or minus 2 but it’s exactly 2.9013! The number is based on a set of differential equations used to model fluid dynamics.

According to a paper by Frederickson and Losada (2005) there is a tipping point in the ratio between positive and negative emotions.… There is only one problem. The math… has recently been demonstrated by Brown and colleagues to be entirely fanciful....