Lesson 1: Don’t trust your brain

Your brain does not think as well as you think it thinks. It’s a crazy hodgepodge of extensions, patches, fixes, additions, and improvements. If it were a computer program, then it would have been written in 8008 assembly language and undergone a steady stream of alterations over the last 50 years, by a series of committees whose members changed every year, and whose specifications and usage requirements shifted from database management to videogames to word processing to web browsing and they still haven’t decided what it should do now. The software is now over a gigabyte in size and is full of bugs. That’s your brain. 

The human brain is not a general-purpose computer. It was not designed from the ground up. Like all organs of all creatures, it is optimized for the living conditions that we encounter. Well, not exactly. There’s a time lag because genetic modification takes thousands of generations to work its way through the system. For the last two million years or so, our ancestors lived what is called a “hunter-gatherer” lifestyle. We’ve been living an agricultural lifestyle for only the last 10,000 years or so. Thus, our brains and bodies are still being built to perform optimally in a hunter-gatherer lifestyle. 

What’s optimal for hunter-gatherers is not necessarily optimal for civilized existence. Let’s start at a simple level by examining the performance of one of the brain’s subsystems: the visual system. Here’s a classic image I’m sure you’ve seen before:


Relativity, by M. C. Escher

Mind-boggling, isn’t it? Actually, it’s more vision-boggling. You know that the scene is physically impossible, yet your eye insists that everything is in its proper place. What’s going on here? 

This craziness is the result of an optimization in your visual system. It is optimized for life in the savannah. It is exceptionally good at inverse texture mapping — that is, it can figure out the shape of an object from slight differences in the texture of its surface. Fro example, look at the heads of the figures in this picture. It’s obvious that they are all round. You know that because of the differences in shading. You also know the angles of the walls because of differences in the gridlike texture of the surfaces. Your visual system is excellent at figuring out local geometric relationships automatically. M. C. Escher took advantage of your visual system’s automatic deductions in order to fool you. 

Here’s another example:


This one should really send your eye into palpitations. It takes advantage of the a number of visual optimizations, but the most important is the way that the eye automatically moves to take in a scene. The sense of the image jittering around goes away when you focus your eye with great determination on any point in the image. If you don’t let your eye move, the image looks stable. When you give your visual system the freedom to analyze the image freely, it jumps the eye around, madly trying to make sense of it.

All optical illusions rely on the fact that they are images that you would never encounter in the real world. Your eye is attuned to the real world and so it can stumble over an image that would never show up in the real world. 

This is not a bug; it’s a feature. You don’t want your visual system to waste precious neurons on the capability to correctly see something that you will never encounter — at least, you will never encounter if you are a hunter-gatherer. 

There are plenty of other behaviors you inherited from your hunter-gatherer ancestors that don’t make much sense now. You’re probably scared of snakes, even if you have never encountered a real snake in the real world. That fear is built right into your genes; everybody shares it, despite that you won’t find many poisonous snakes slithering down Main Street or on the 8th floor of your apartment building.

Or how about those emotions that rampage through your mind? When was the last time that getting really angry saved the day? Or how about that time that you were so scared that you couldn’t respond to a dangerous situation? Did it turn out well when you acted on your arousal by a member of the opposite sex? If you’re a hunter-gatherer, it’s wise to get angry at any opponent; the anger triggers adrenalin that summons your greatest physical strength, preparing you to fight or run, as necessary. Anger is a good thing for hunter-gatherers, but for civilized people it’s usually a source of grief. For the same reason, fear is a good thing in world populated by lions, tigers, and bears, but you can’t save yourself from an onrushing car with a punch in its face, nor can you outrun it. You have to use your wits, not your muscles. 

When I was in grad school, we had an old VW pickup truck that wasn’t in the best of shape. I did my best to keep it running, but one cold day my wife took it to go shopping and, upon returning to the truck with her bag of groceries, found that it wouldn’t start. She tried everything she could think of, but it just wouldn’t start. She went to the back of the truck, pulled a steel bar out of the truck bed, and began hitting the side of the truck with the steel bar, yelling at the top of her lungs. It didn’t work; the truck was not intimidated into starting. 

One of my own little brain bugs is the remixing of letters in signs I see. While driving north on Highway 101 in Sunnyvale one day, I saw a sign outside the government airfield at Moffett Field. I blinked when I read “Winos over Moffett”. It was an advertisement for an upcoming air show. 

Then there was the time I was walking through a department store and passed by a sign advertising one of those devices you place in the bottom of your kitchen sink to chew up kitchen garbage so that it can safely pass through the pipes. But I couldn’t figure out why it was labeled “Stink Master”. 

I have an old book presenting newspaper bloopers from the 1980s. Here are some of the headlines shown in the book:

Defendant’s speech ends in long sentence
Silver objects often taken — police units seek pattern
Sharks Stop Search for Span Collapse Victims
Garden Grove Resident Naive, Foolish Judge Says
Give the Palestinians a Homeland — Ottawa
‘Mild’ Fertility Drug Produces Quadruplets in 3 Minutes
Here’s How You Can Lick Doberman’s Leg Sores
Sisters Reunited After 18 Years in Checkout Line at Supermarket

But my favorite is an unfortunate combination of two stories. The first story tells about President Ronald Reagan visiting a school; a large photograph shows him seated beside a young boy in front of a computer. The President is smiling and placing his hand on the little boy’s shoulder. Next to that photograph is another story with the headline “Child Molesters Indicted”

The world of finance shows how easy it is for humans to make stupid mistakes. Economists are just now beginning to realize that real people do not act in the most economically rational manner. For example, consider a clever experiment in which half of the people in a group were given a free mug. The authors then asked each person who did not receive a mug how much they would pay for the mug. Then they asked each of those who had received a mug how much they would sell the mug for. Now, if people were perfectly rational, then there is a “correct” valuation of the mug that applies to large groups of people. The people on both sides should, as a group, have about the same assessment of the “correct” value of the mugs, and so the personal valuations should closely match, and about half of the mugs would be sold. But that’s not what happens. The people with the mugs valued their mugs at a price higher than the people without the mugs. Consequentially, fewer mugs traded hands.

An even simpler example comes from a psychology experiment involving a gambling game. Each subject is given one dollar, then offered the option for a simple gamble: a coin will be flipped and if it comes up heads, they win $2, but if it comes up tails, they forfeit their dollar. A simple calculation of probability shows that it’s an even deal; the probability is that, if you take the bet, you’ll come out the same. Yet people seldom accept the bet. Losing what you have is generally perceived to be of greater import than gaining the same amount.

You can find a depressingly long list of cognitive errors on Wikipedia. Humans just can’t think straight.

Here’s a particularly telling example of the weaknesses of human reasoning. Let’s play a game. Here’s the wording used by the scientists who discovered something fascinating about the human mind:

Part of your new job for the City of Cambridge is to study the demographics of transportation. You read a previously done report on the habits of Cambridge residents that says: "If a person goes into Boston, then that person takes the subway."

The cards below have information about four Cambridge residents. Each card represents one person. One side of a card tells where a person went, and the other side of the card tells how that person got there. Indicate only those card(s) you definitely need to turn over to see if any of these people violate this rule.

Try it. You may well have difficulty figuring out the answer. I’ve placed the answer after a long vertical gap on this page:

Answer: you must turn over the Boston card and the Cab card. But now let’s do a different version of the same test. In this version, a mother has left her four children alone for the evening, but told them that any child who completes their homework may have a cookie. These four cards show what each child did, again with one half of the child’s action on each side of the card. Which card(s) would you have to turn over to determine if any child broke the rule?

Figure it out. Again, the answer is a long ways below this.

Answer: turn over “did not complete homework” and “ate a cookie” to see if a child cheated. 

Now, if you’re a normal member of species Homo Sapiens, you probably had an easier time answering the second test than the first one. Yet the two questions are logically identical! They should have been equally difficult, but most people can’t figure out the first test and can figure out the second test. There’s a good reason for this difference, and it reveals how the human brain is not at all a rational processor. 

There are many more examples of human mental quirks. Your brain simply does not perform the way you think it should. Therefore, if you desire to think more clearly, you must be acutely aware of the many ways that your brain misinterprets, misunderstands, and misjudges. Never trust it. But if you learn what those quirks are, and how they work, then you can correct for them and think more clearly.

Lastly, if you are still in doubt regarding human stupidity, I offer you absolute proof of the idiocy of the American people: 

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