Trying to make sense of nonsense

The life and times of Paul the perfectly normal octopus: a feature film

Paul the very regular octopus

Picture by Alvaro Felipe

I don’t care about football. To me, it’s just a bunch of guys running across a field being paid enormous amounts of money (Rooney’s weekly salary could fund three entire 3-year PhD studentships) to kick a ball into a net. But the last World Cup did manage to spark my attention. Not because ‘my country’ happened to make it to the final, but because there suddenly was the media hype around Paul, the so-called psychic octopus. Now, psychic animals can provide a good amount of entertainment – let Groundhog Day be the evidence of that – but when people actually start believing in the clairvoyant abilities of a cephalopod something must be awry. With 8 out of 8 correct predictions for World Cup matches last year, the odds did seem to be on Paul’s psychic side, but the feature film “the life and times of Paul the psychic octopus” aims to put those speculations at a rest.

While the trailer is all that is available at the moment, the evidence for Paul’s ability to see the future has been discussed far and wide. As mentioned, Paul predicted 8 out 8 matches right, so the chance of him predicting all of these right by pure luck were 1 in 256 (or 28), which is seemingly a pretty small chance. What actually happened was a bit like a lottery: the chance of one individual guessing the winning numbers is pretty slim, but the chance that someone, anyone, wins is a lot bigger. During the World Cup there were lots of animals trying to predict the outcomes of matches. Mani the parakeet was one of those more famous others who made it pretty far, but there was a vast array of rabbits, horses and guinea pigs doing the same thing. But as with a lottery, only the final winner, the one who guessed (or predicted if you like) all the numbers right made it into the spotlight.

The chances of Paul being psychic seem a lot less when all the other less lucky animals are taken into account. However, there is another aspect to be taken into account: what is the chance that Paul is psychic to start with, and how does the evidence – his 8 right predictions – change this? This is also known as Bayes’ theorem: the chance of something being true is influenced by the initial, or prior, chance. As obscure as that may sound, it is a common feature on a show such as House MD (and in medicine in general). When a slim 18-year old girl gets brought into House’s ward with a heart attack, and all the tests point to a heart attack, Dr House will usually not be convinced as slim 18-year old girls just don’t get heart attacks: it’s a disease for the old and obese. Therefore the cause must be a rare disease that makes it appear as if the girl is experiencing a heart attack and messing up the tests. House always turns out to be right.

The same holds true for Paul: the chances of him being psychic are really low to begin with, if not completely absent (and if you do happen believe that there are lots of animals out there that can see the future, I do hope that you are a vegetarian, as it would be terribly cruel to be killing and eating creatures who know exactly what’s coming for them). The evidence of Paul predicting 8 winners right can, with a bit of maths, be shown to triple the chance of Paul being psychic, as shown here by Prof David Spiegelhalter. As the chance of an octopus being clairvoyant are next to non-existent to begin with, even tripling these chances doesn’t have much of an effect. Interestingly, if you would start out thinking that it is impossible for Paul to be psychic, this would remain true whatever evidence would pop up.

And that are just the statistics. Paul might have guessed the winning team for other reasons. Paul had a real affinity for the German flag, picking it 5 of the 7 times it was presented to him. He might have liked the look of the flag (even though octopodes are practically colour blind), or he might have picked up signals from his German carers, who were rooting for Germany to win. As Germany had a pretty decent team and thus a good chance to win matches, this patriotism might have given Paul an unfair chance compared to his fellow psychics from countries with lesser football teams.

And finally, there were the footballers themselves. They were likely to have heard about Paul and his predictions during the tournament and they are a gullible lot, as evidenced by the popularity of ‘Power balance bracelets’ among them. These bracelets were said to improve balance through “a thin polyester film hologram programmed through a proprietary process which is designed to mimic Eastern philosophies that have been around for hundreds of years,” or to put it in other words: a fancy shiny sticker. All of the players in the World Cup final wore these bracelets, and if they could be convinced that a sticker would improve the ability of players who train relentlessly (or so I may hope for the pay they get), they might as well be swayed by the predictions of a perfectly normal octopus.


2 responses to “The life and times of Paul the perfectly normal octopus: a feature film

  1. Pingback: Is Nate Silver a witch? « epidemiologista

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