The one-sentence summary

People will make irrational decisions if left to their own devices.


  • We usually think we are rational beings but the science of decision-making would suggest otherwise. Logical thought can be subverted or ‘swayed’ in many ways
  • Irrational behaviour can be perpetrated by the most experienced and well-trained people, including pilots and doctors
  • Common reasons are: overreacting to a potential loss, taking dangerous risks when a lot is at stake, refusing to withdraw even with a small loss, misjudging something because it is in the wrong context, and being prejudiced by prior information
  • Our brains have two particularly different parts that are constantly struggling with each other: the ‘pleasure centre’ wild side that gets a kick out of taking risks, shopping, winning money etc., and the ‘altruism centre’ that does the best for others and always seeks reasonable compromise
  • Sometimes it just doesn’t seem worth the bother to dissent from the prevailing view, so many people stay quiet when the majority have got it wrong – particularly for an easier time at work


  • There are scores of examples from anthropology, aviation, sports and politics to illustrate the points
  • The narrative rolls along nicely – more story than text book
  • The thesis is a useful complement to, and development of, many other social theory books of recent times: Freakonomics, Nudge, Herd, and The Tipping Point


  • It is this very similarity to so many other books that makes it potentially derivative. Although in theory it is original material, sometimes it feels too similar. A shorthand for separating them is:
  • Freakonomics: patterns of social behaviour can be rooted in linked causes
  • Herd: huge numbers of people simply copy each other because they are social
  • The Tipping Point: little things can make a big difference
  • Nudge: providing different options or small incentives can change mass behaviour
  • Sway: irrational behaviour can affect even the best-trained and the most experience people