Lost in the Land of the Liars: PYP 371

There's a logic puzzle, well-known to those of us who never dated in high school, about an island that's inhabited by two tribes – the Liars and the Truthtellers. As you might guess, the Liars always lie, and the Truthtellers always tell the truth.

It's impossible to tell them apart by looks.

You're on this island, at a fork in the road, lost and confused, and you want to know which road takes you to the village. You're especially keen to know this because the other road leads to a dangerous dragon. You see a native of the island walking by, and get to ask one question. But you don't know which tribe they're from. What one question can you ask to find your way to the village?

Let's say you ask the obvious question: “Which path goes to the village?”

And let's say the correct answer is “the left one.”

If the person you ask is a Truthteller, they'll say, “the left one.”

And if they're a Liar, they'll say, “the right one.”

But since you don't know whether you're getting the truth or a lie, you're no wiser after asking that question.

What if I changed the rules for you and allowed you more than one question? What happens if you inquire which tribe they belong to before asking for directions?

Both will answer, “I am a Truthteller.”

Again, no help.

So is there a single question that can tell you how to get to the village?

Yes there is!

And before I share it with you (in case you were the sort of person who dated in high school and didn't spend Saturday nights with books like Martin Gardner's Perplexing Puzzles and Tantalizing Teasers), let's talk about why it's relevant to our health.

The Questions We Keep Asking Ourselves

Many of us have spent decades beating ourselves up for the knowing/doing gap: the difference between our intentions and our actions.

When faced with evidence that we aren't behaving in ways that will help us lose weight, get fit, reverse chronic conditions, and make us happy, we're perplexed. Why am I self-sabotaging? What's wrong with me?

And the brain is a very eager bloodhound; give it a sock to smell, and it will spend the rest of time looking for its owner until it finds a match.

If the sock you give it is the question, “What's wrong with me?”, then your brain will dutifully bring you back answers. Sometimes they sound like these:

* You are lazy.

* You are undisciplined.

* You don't want it bad enough.

* You have a sweet tooth.

* You had a traumatic childhood.

* You're not a morning person.

* The world is out to get you.

Your Brain is Tyler Durden

The problem is, your brain is what's known in literary criticism as an “unreliable narrator.” Not because it's necessarily trying to deceive you, but because it's compelled to give you the best answer it can even though it doesn't have a freaking clue.

Unreliable narrators are dangerous only when we don't realize that they're unreliable. And our own brains are the most notorious unreliable narrators of all. As rock star physicist Richard Feynman said, “The first principle is that you must not fool yourself and you are the easiest person to fool.”

Or as Emo Philips puts it, “I used to think that the brain was the most wonderful organ in my body. Then I realized who was telling me this.”

Your brain has no idea why you're not following through on your good intentions. So it looks at the evidence and, not to put too fine a point on it, makes shit up.

We learned about the brain's willingness to make shit up from what are known as “split-brain experiments.”

Split-Brain Experiments

One surgical treatment for severe epilepsy involves severing the corpus callosum; the bunch of cables that connect the right and left hemispheres of our brains....