I enjoy hearing about or even falling for a good harmless prank — and I certainly enjoy pulling a child or two’s string, in a cheerful, happy way, just to keep them on their toes — so, April Fools’ is one of my favorite days of the year.

The holiday underscores how important surprises are for our brains. Of course, one hopes those surprises will be delightful ones!

Your brain is actually masterful at connecting the dots and jumping rapidly to a strong conclusion. Making quick decisions on the basis of limited evidence has been a key to our survival on the planet. It’s one of humankind’s greatest strengths — and weaknesses. We’re continuously making quick decisions. But, sometimes, your brain is a little too quick, and a little too decisive, and the trap can be sprung.

If all is in good spirits, the discovery of being led down the garden path can be almost as much fun for the “victim” as for the “perpetrator!”

Brain Chemistry When You’re Fooled

Your brain releases several special “modulatory transmitters” (chemicals that change your brain in a positive way), whenever you are pleasantly surprised. For example, norepinephrine and acetylcholine flood the brain whenever something unexpected or novel occurs in your world. If it's a positive or delightful surprise — as it is when you discover that you’ve been the successful perpetrator or recipient of a clever and warm-spirited prank — you feel rewarded, and your brain also releases dopamine.

Norepinephrine release is all about “turning up the lights,” to sharpen your attention, given that something unexpected has just occurred. Acetylcholine supports your brain’s recording and remembering that surprising event, which will help assure that you won’t be so easily fooled the next time around! Dopamine supports your happy delight. Their combined good effects are a large part of the reason why we enjoy a happy surprise so much.

Brain Chemistry May Be Why April Fools Day Has Been Around For 1400 Years

This mix of brain chemicals helps explain why this peculiar little holiday — neither religious nor historic — has been celebrated all over the world for a very long time, dating at least back to the 6th Century BC in Persia. In France, there’s a tradition of taping a paper fish onto someone’s back on “Poisson d’Avril” — literally, “April Fish!” In Scotland, they love a prank so much, they extend the holiday to include April 2nd. In England and Germany, they’re more efficient — all pranks must be completed by noon. No matter what the specific traditions, it’s all about that special form of foolery that most often results in a happy “you got me” laugh.

Why We Fall For It

So, why is it the brain gets fooled? We humans have lots of tricks to convince others that something false is true. You may not be convinced by me saying something is so, but, if I can compound enough evidence to build credibility, I may succeed in my deception.  Maybe I get Mom to come in on the trick. Now, you’re caught off guard, because Mom is a well-known teller of truth. Maybe you adopt a tone of voice, or a turn of phrase, that captures your victim’s imagination, resulting in a wrong turn.

Some people have exceptional skill in misleading others. Magicians do it professionally and have quite a bag of tricks. Your brain is sampling information moment by moment, and in the intervals between those moments — as they deflect your attention, so you don’t see it — magicians can move an elephant across the room.

A Mistake Induced by Others

It’s actually pretty easy to fool — or be fooled by — another person. It’s one of our important strengths and weaknesses. Of course, we all make mistakes, all the time. Sometimes, we believe strongly in things that are false. People may witness a crime and be sure who did it, but studies have shown that eyewitness testimony is not all that reliable.

In my case, I wrote an autobiography to share the stories of my youth with my grandchildren. Then, I was surprised to discover that my five siblings had very different recollections of many details (of which I had quite vivid memories).We are capable of fooling ourselves and holding strong beliefs that are not accurate. Of course, when it came to the different recollections of childhood put forth by my brothers and sisters, I had to tell them to write their own damn book.

But here’s the thing. Due to revolutionary advances in brain science, and particularly the ability to reduce error rates, we know that we can now sharpen the brain, so that we virtually never will make mistakes (other than perhaps on April Fools’ Day, just to maintain our old traditions).

And, if you believe that… April fool!