A simple principle that explains everything from the perceived success of speed cameras and alternative medicine to the Sports Illustrated jinx

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.

Regression to the mean can be used to explain the success of alternative medicine (i.e. any intervention that has not passed the test of randomised controlled trials). This is due to the fact that people often tend to get better by themselves given time - they regress to the mean. Statistically, having a headache for example, is an extreme situation. You're most likely to seek help for symptoms when the pain is at its most severe. If you have a headache and take a homeopathic pill you might feel better because of the placebo effect - but you might just feel better because your headache passed all by itself - regression to the mean. This can be a problem for all kinds of research if an experiment is not carefully controlled. If a patient group is selected for their extreme symptoms we can expect that as a group their condition will generally improve over time regardless of any intervention.

A thought experiment presented by Daniel Kahneman is to consider the case that "highly intelligent women tend to marry men that are less intelligent than they are". Take a moment to think about that. As humans, we naturally tend to spot patterns such as this and come up with our own causal explanations. The solution proposed by Kahneman is somewhat more straightforward: "If the correlation between the intelligence of spouses is less than perfect and if men and women on average do not differ in intelligence then it is a mathematical inevitability that highly intelligent women will be married to husbands who are on average less intelligent than they are - and vice versa of course". Whether we like it or not we are programmed to seek causal explanations even when they do not exist and that is something we need to actively remember if we don't want to be misled - or mislead ourselves.

It's staggering how few adults understand the concept of regression to the mean, but it really is a concept worth getting to grips with. This video introduces the concept beautifully:

Related post: How being called smart can actually make you stupid.

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Researchers at the University of Colorado Boulder found that the fatty 10(Z)-hexadecenoic acid from the soil-residing bacterium Mycobacterium vaccae aids immune cells in blocking pathways that increase inflammation and the ability to combat stress.

The study's senior author and Integrative Physiology Professor Christopher Lowry described this fat as "one of the main ingredients" in the "special sauce" that causes the beneficial effects of the bacterium.

The finding goes hand in hand with the "hygiene hypothesis," initially proposed in 1989 by the British scientist David Strachan. He maintained that our generally sterile modern world prevents children from being exposed to certain microorganisms, resulting in compromised immune systems and greater incidences of asthma and allergies.

Contemporary research fine-tuned the hypothesis, finding that not interacting with so-called "old friends" or helpful microbes in the soil and the environment, rather than the ones that cause illnesses, is what's detrimental. In particular, our mental health could be at stake.

"The idea is that as humans have moved away from farms and an agricultural or hunter-gatherer existence into cities, we have lost contact with organisms that served to regulate our immune system and suppress inappropriate inflammation," explained Lowry. "That has put us at higher risk for inflammatory disease and stress-related psychiatric disorders."

University of Colorado Boulder

Christopher Lowry

This is not the first study on the subject from Lowry, who published previous work showing the connection between being exposed to healthy bacteria and mental health. He found that being raised with animals and dust in a rural environment helps children develop more stress-proof immune systems. Such kids were also likely to be less at risk for mental illnesses than people living in the city without pets.

Lowry's other work also pointed out that the soil-based bacterium Mycobacterium vaccae acts like an antidepressant when injected into rodents. It alters their behavior and has lasting anti-inflammatory effects on the brain, according to the press release from the University of Colorado Boulder. Prolonged inflammation can lead to such stress-related disorders as PTSD.

The new study from Lowry and his team identified why that worked by pinpointing the specific fatty acid responsible. They showed that when the 10(Z)-hexadecenoic acid gets into cells, it works like a lock, attaching itself to the peroxisome proliferator-activated receptor (PPAR). This allows it to block a number of key pathways responsible for inflammation. Pre-treating the cells with the acid (or lipid) made them withstand inflammation better.

Lowry thinks this understanding can lead to creating a "stress vaccine" that can be given to people in high-stress jobs, like first responders or soldiers. The vaccine can prevent the psychological effects of stress.

What's more, this friendly bacterium is not the only potentially helpful organism we can find in soil.

"This is just one strain of one species of one type of bacterium that is found in the soil but there are millions of other strains in soils," said Lowry. "We are just beginning to see the tip of the iceberg in terms of identifying the mechanisms through which they have evolved to keep us healthy. It should inspire awe in all of us."

Check out the study published in the journal Psychopharmacology.

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