According to urban legend, sports stars who appear on the cover of Sports Illustrated will subsequently experience bad luck. This seems counterintuitive but time and time again the Sports Illustrated jinx repeats itself. Take another example that at first might seem unrelated: Flight cadets have been noted to improve in performance immediately following punishment and show poorer performance immediately following rewards - a finding that seemingly flies in the face of much of what we know about behavioural psychology. Think about your own life for a moment, have you ever noticed this effect? Why might this be the case?
In both cases, as Nobel prize winning economist Daniel Kahneman explains in Thinking Fast and Slow, the answer is nothing to do with what we might expect - the fact that the sportsmen and women appeared on Sports Illustrated or the way the flight cadets were rewarded or punished. The real explanation is all down to probability - a principle known as regression to the mean. Wherever we can expect random fluctuations, if we take an extreme example such as a sportsmen who is on a winning streak or a flight cadet performing particularly well or badly, we can expect that in the immediate future their performance will return closer to the mean due to chance alone. A classic example of this is in how we interpret the effect of speed cameras which are typically installed following a streak of accidents. Following a streak of accidents we can expect that due to random chance there will be a period of time where no accidents take place, regardless of whether or not a speed camera is installed - but when a speed camera is installed we attribute the subsequent immediate drop in accidents as a result of the speed camera.