Posted by: Craig Woolheater on July 19th, 2013
When I was a shaver, I believed there was a creature called Bigfoot, and I could support this belief with evidence. Many cultures have stories of a shaggy-haired man-like reclusive creature. Many reputable people say they think they have seen or heard such a creature. There are blurry photos and videos that show what looks like Bigfoot. Scientists have found footprints in the snow that are too large to be made by any known animal. And so on.
When sceptics argued my evidence might have another causes, for example pointing out that the freezing and thawing of ice can make the footprint of a bear or wolf much larger over time, I was unmoved, because my theory explained all the evidence I could see.
But then someone smart asked me a question: “Where is Bigfoot’s poop?”. I saw the logic immediately. Given that Bigfoot is large and uses lots of energy roaming widely in the forests, he needs a lot of calories to keep going. That means he must eat a lot. And as he is a humanoid, he presumably excretes the remains of his meals. He himself may be reclusive, but his poop wouldn’t be. So why don’t we find his spoor as we do that of every other creature? Does he carry it with him in an American Tourister bag or something? This point shattered my faith in Bigfoot.
Psychologist Daniel Kahneman’s marvelous book Thinking Fast and Slow well describes the basic cognitive limitations that made me (and many other people) believe in Bigfoot. The first is the tendency to see common themes where they aren’t any, which made Bigfoot seem to me the logical, essential thread connecting all my disparate “evidence”. The other is that the human mind focuses on what is in front of it while being poor at accounting for what is not present, like Bigfoot’s poop.
Whoever asked me the poop question (I wish I could remember so that I could thank him or her) didn’t try to dispute the evidence which I thought supported my theory. Rather, they took my theory as correct and then pointed out that what followed logically from it was not in evidence. Some people cannot be argued out of strange theories for emotional reasons, but those who can are more likely to be susceptible to this style of counter-argument than they are a direct attack on their observed evidence.
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