We all use silly logic to help us rationalize a confusing world.

Take full moons, for example.

For centuries people have been blaming full moons for inexplicable behaviors that coincided with them.

But its an illusory correlationwe fool ourselves into believing something based on what stands out most in our memories.

This post originally appeared onJames Clears blog.

Human beings have been blaming strange behavior on the full moon for centuries.

In the Middle Ages, for example, people claimed that a full moon could turn humans into werewolves.

In the 1700s, it was common to believe that a full moon could cause epilepsy or feverish temperatures.

We even changed our language to match our beliefs.

The wordlunaticcomes from the Latin rootluna, which means moon.

Today, we have (mostly) come to our senses.

Whats going on here?

The nurses who swear that a full moon causes strange behavior arent stupid.

They are simply falling victim to a common mental error that plagues all of us.

Psychologists refer to this little brain mistake as an illusory correlation.

Heres how it works.

Then, you go to a restaurant and the waiter is rude to you.

Finally, you ask someone on the street for directions and they blow you off.

These were literally non-events because nothing notable happened.

Lets break down the possibilities for having a full moon and a crazy night of hospital admissions.

Cell A:Full moon and a busy night.

This is a very memorable combination and is over-emphasized in our memory because it is easy to recall.

Cell B:Full moon, but nothing happens.

This is a non-event and is under-emphasized in our memory because nothing really happened.

It is hard to remember somethingnothappening and we tend to ignore this cell.

Cell C:No full moon, but it is a busy night.

This is easy to dismiss as a crazy day at work.

Cell D:No full moon and a normal night.

Nothing memorable happens on either end, so these events are easy to ignore as well.

This contingency table helps reveal what is happening inside the minds of nurses during a full moon.

Meanwhile, you never hear about all of the college dropouts that fail to start a successful company.

You never hear about the 99 percent of people who dont get arrested because it is a non-event.

You over-emphasize the story you hear on the news and make an illusory correlation.

We are incredibly poor at remembering things that do not happen.

If we dont see it, we assume it has no impact or rarely happens.

Image byBplanet(Shutterstock).