Why do people believe weird things?

Many people believe many things that aren't true, or that aren't provably true. Whether it's something to cure the common cold, cause bad luck, or guaranteed to make money fast there are many who buy it, avoid it, invest in it, and tell their friends how it worked for them.

There are many websites debunking such things or embracing science that shows what is true or false. Skepchick and Snopes are two I like.

But today I wonder why people believe weird things.

People develop superstitions easily.
I had a friend years ago who wore the same sweatshirt a few times while watching his favorite sports team win on TV. He developed a belief that he had to wear that sweatshirt during a game in order for the team to win. This pattern is very common. The same thing happens a few times in a row and people believe it is "always" true. Once the superstition is established people remember the events that reinforce it and discount the events that don't. Have you ever thought or said something like:
- "This traffic light is always red."
- "This line at the grocery store is always faster."
- "My gate at the airport never changes."
- "I never loose my keys."
- "I catch colds more than most people."
- "It always rains on holidays."
Chances are the light, line, gate, etc. is random and your perception is wrong. The only way to know is to carefully track the events so you have solid data to counteract your selective memory.

The human brain is great at finding patterns.
It's so good at finding patterns that it finds them where they don't exist. Have you ever found shapes in clouds? I used to do that as a child; lie on the grass and watch the clouds go by and call out ones that looked like a ship or a bunny. Of course the similarity is only coincidence, there is no mechanism causing a certain cloud to specifically resemble a rabbit. Evolution clearly favored the ability to find every real pattern (and some false ones) over avoiding false patterns (and missing some real ones). I don't know why recognizing patterns is so beneficial but I'm sure there's an evolutionary biologist or evolutionary psychologist with a good hypothesis.

Logical fallacies are difficult.
Okay, maybe they're not difficult to understand while reading about them or during a formal debate, but most people don't internalize that understanding well enough to recognize logical fallacies at other times. Two common ones are:
- "Post hoc ergo propter hoc." That's Latin for "After this therefore because of this." The fallacy is thinking that since B happened after A, B was caused by A. I think this fallacy explains why so many people believe vaccines cause autism. The age when autism symptoms usually first show up is after the MMR vaccine is routinely given. So when those poor parents hear this horrible diagnosis the most recent event in their child's life was that vaccine. But believing that causal relationship makes as much sense as believing that breakfast causes lunch or that fifth grade causes puberty.
- "Correlation does not indicate causation." Lots of things increase or decrease at the same time, but that's mostly coincidence. Over time the population increases and the year number increases. That doesn't mean that incrementing the year makes the population go up. Further, if we decide next year is year 10,000 and then we'll count backwards every year, that won't make the population go down. But it's easy for someone to assume causation when they see a correlation, and easier when there's an official looking line graph.

People tend to believe other people.
Humans are social. We thrive when get along with each other and learn from each other. So when a friend says "This supplement cured my cold" or "This stock is certain to go up" people tend to believe it. It's more social, easier, and more pleasant to trust one's friends (or newscasters, priests, aerobic instructors, etc.) than to do one's own analysis. So once an unproven or incorrect idea is out there it tends to spread.

Most people don't trust the scientific method.
The scientific method is the best tool we have to understand our universe. Sadly, most people picture science as the combination of books full of facts and authority figures who call themselves scientists. Most people don't know (or don't think about) the process that finds all those facts. Many people trust the Bible more than science texts and clergy more than scientists...and they think these things are similar.

So there are reasons why people believe various sorts of woo; understandable, human reasons. But I think it is responsible to question one's beliefs, assess the evidence, and discard unsubstantiated beliefs.