Caveman Logic: The Persistence of Primitive Thinking in a Modern World (4 page)

The bottom line is that when you think of ancestors, you’re likely to stop the search at the level of great-grandfather. When you think of history, images of George Washington often come into view. Neither is particularly relevant to the issues in this book. The ancestors we have in mind here are shared by you, me,
and
George Washington. We’re talking about our
species’
ancestors. Whether we like it or not, the solutions to their numerous struggles are reflected in our genome today. For better or worse, their successes are translated into the mental and physical equipment we carry with us in the modern world. We’re talking about far more than eye color or hair texture. These are about basic, species-wide human qualities and predispositions. They are there whether your hair is curly or straight, blond, brunette, or receding fast.

And there you have it. A journey that began its final leg about 6 million years ago, simmering without much change for much of that time, suddenly coming to a boil in the last half a million years and then reaching a frenzy of activity during the past 50,000 to 100,000 years—an era called the Pleistocene. This “history” is plainly very different from the images conveyed by Julius Caesar, Abraham Lincoln, or World War II. It is also ancient and lengthy. And through it all, our species was undergoing physical and mental changes that best adapted it to life under conditions that barely resemble our present world. The genetics that underlie these adaptations were carried forward even after they ceased to be particularly useful. As the expression goes, “Evolutionary wisdom is past wisdom.” It is always out of date. It reflects where we came from. The proverbial Cradle of Life is where our minds were formed.

The human mind is an illusion generator. Since you
have
a human mind, that statement probably either feels wrong or like an insult. It is neither. Patterns are everything to us. We hunger for them. We revel in them. They are the basis for art, literature, music, and much more in our lives. But a perceptual system that is so geared to wrestling patterns out of complex arrays of stimuli is bound to produce some false positives. From time to time we are going to see or hear what is not there, and those cases will seem no less compelling to us. They are the territory of this book.

You have sense organs (we’ll focus on the eye and the ear) and an apparatus for interpreting the information those organs provide. That’s where your mind comes in. Strictly speaking, we are talking about your brain, which is a modular organ. Our focus here is with the
interpreter function
—the part of your brain that takes all those raw sensory impulses just forwarded by your eyes or ears and does its job by trying to make sense of what it has registered. There are a lot of other jobs your brain does—it regulates your body temperature, controls your arousal level, modulates your response to pain in your left foot, and so on. All of those things and a lot more are beyond the scope of this book. It is that function of the brain we loosely call “the mind” that is our focus.

Technically speaking, our eyes and ears are flawed too. Yes, they are a marvel of engineering that took millions of years to evolve. But they are incomplete: they are not responsive to all the sights and sounds out there. In fact, they are responsive to a very narrow range of what exists around us. Imagine a line stretching for over a mile. It represents all the stimuli, the physical waveforms if you prefer, that you might see or hear. Now imagine going up to that very long line and sticking a pin into it. The head of that pin represents the range of stimuli you can actually see and hear. All the rest in both directions is beyond your capability. For some people, that news alone is startling. They’ve always assumed they can see and hear everything there is to see and hear. It’s true that older folks may need eyeglasses or a hearing aid, but prior to that all the sensory information in the world must have been getting through, right?

Nothing could be further from the truth.

As rich and beautiful as the world may look and sound to us, it is based on a tiny little bandwidth of raw sensory information that we manage to glean. For example, wavelengths longer than those for the color “red” are called “infrared.” We cannot see them. Similarly, wavelengths shorter than those for the color “violet” are called “ultraviolet.” Again, we are blind to such energy, although it is measurably present all around us. Our ears are similarly insensitive to sound waves that lie above or below the audible part of the spectrum (roughly between 20 and 20,000 Hz or cycles per second). The energy is there. Some of it we might have heard when we were younger or before we attended too many rock concerts. But, even then, we were relatively impoverished. Those other wave frequencies just couldn’t get through. Our problem was simply that we are human.

Nevertheless, the information we do see and hear seems enough; it constitutes reality to us and gives us the illusion of a complete world. We may be vaguely aware that other animals see and hear different things than we do. Dogs (and rats and many other mammals) can hear high-frequency sounds we can only imagine. Bees can see polarized light; hawks can see accurately at distances we can approximate only by using high-tech intervention.

But, the truth is, none of these sensory deficits matters as much as the limitations of our mind. We don’t
need
to see and hear everything out there. We are getting more than enough raw sensory information to function at a very high level. It is what we make of those raw sensations that creates problems. Those cognitive and perceptual problems are the subject matter of this book. The science of psychology makes the distinction between sensation and perception. Sensation refers to the structure and activity of our sense organs. Again, that is not the focus of this book. Perception, on the other hand, is. How we perceive the world is the story of what our minds do with those raw sensory inputs. Once our minds get involved in the process, we are in for a bumpy ride.

Most Introductory Psychology textbooks contain sections on optical illusions. There are relatively few of them and they are well studied. Most students enjoy reading about them because, like watching magic tricks, they provide some excitement. They violate your expectations and create experiences that you
know
can’t be happening in the real world. But even optical illusions are just a hint of the mental distortions that are part of our everyday lives.

Introductory Psychology books also contain sections on common errors in thinking. These come a lot closer to our concerns here. Compared to optical illusions, these cognitive shortcomings are less well studied, although that is starting to change. They go by different names such as “heuristics” and “biases” and often appear in chapters of Introductory Psychology books labeled “cognitive psychology.”
⁶
There is even some controversy over whether they are assets or liabilities. In truth, they are both. The real problem is our failure to recognize them for what they are and take steps to remedy them.

Let’s consider a simple example. If you depended strictly on a literal interpretation of your sensory evidence, there would be good reason to believe that (1) Earth is flat, and (2) the sun, moon, and stars rotate around our planet, which remains fixed at the center of the universe. In fact, that is exactly what people believed until fairly recently in human history. They did not question the evidence of their senses and found it both threatening and, in some cases, quite offensive to have these beliefs challenged.

The reason their beliefs were challenged is that scientific advances provided more-sophisticated ways of gathering evidence. This new evidence became more and more difficult to ignore and it bore directly on how we saw our planet and its place in the solar system. As word spread, it became increasingly threatening to certain institutions whose power was vested in the status quo, no matter how wrong it was. The Catholic church, for example, used all the authority at its disposal to suppress the idea that Earth revolved around the sun, and it brought severe penalties (ranging from excommunication to death) to those, such as the astronomer Copernicus, who professed an alternative viewpoint. Institutional resistance is not uncommon in cases where science challenges widely held but outdated viewpoints. Although not as powerful as the Catholic church, there remains to this day a Flat Earth Society.

This is not simply ancient history. It has everything to do with issues facing us today. Ask yourself why flat earth and center of the solar system beliefs were so widely held a thousand years ago. The answer quite simply is that the human mind did the best job it could with the available evidence of its senses, and that the conclusions it reached, however wrong, were socially supported. The person on the street in the year 1242 had essentially the same mind you do. He had far less information than you have, but he was subject to the same perceptual illusions, needs, and social pressures that you are. Arguing about Earth’s place in the universe made no sense because, as far as he could tell, the status quo seemed right. Moreover, it felt good, even comforting, to think that he and his family were important enough to be living at the center of the universe. And, speaking of his family, they all seemed to share this view, as did his closest friends and associates. Challenging this view, even if he had some evidence or doubts, would only bring conflict. Life was stressful enough already.

And so for many years Earth remained flat and at the center of the universe, at least according to popular belief. Don’t make the mistake of believing that such ignorance or defensiveness was confined to the Middle Ages. Transitional times, as far as ideas are concerned, are often ugly periods in human history. Arguably, such ignorance and resistance are even more egregious during more-enlightened times like the present.

In some ways, we are the lucky ones. Our civilization has never been as knowledgeable as it is today. There has never been as much scientific understanding of the world around us as there is right at this moment. We have put many faulty beliefs behind us. Yet, because our minds are no more evolved than they were a thousand years ago, we are just as vulnerable to illusion, comfort, and social pressure as our ancestors were. Faced with incomplete sensory evidence, we are just as likely to come to wrong conclusions and then fight passionately to maintain those views because of the comfort or stability they provide. We may be less ignorant than our ancestors, but all the hard-won additional information does us no good if we don’t let it inform our thinking.

Broadly speaking, there are two ways you can make a perceptual mistake: You can fail to see something that is there, or you can see something that isn’t there. Neither is good, but as errors go, these two mistakes may not be equally costly. Imagine that you’re in charge of designing the justice system for a new society. If your citizens decide the worst thing that can happen is to let a murderer go free, then you will require a fairly low standard of evidence. In this way, you’ll probably catch every murderer in sight. Nobody will escape detection. The problem is, you’ll probably also prosecute a few people who weren’t actually murderers. Think of these as
Type I errors
. By allowing a few Type I errors (i.e., “false positives”) to occur, you worry a lot less about real murderers going free. Those are called
Type II errors
, and you’ve just about eliminated them in your system.

But imagine that your new justice system has a different set of priorities. What if its primary concern is to never execute an innocent man. In other words, Type I errors are absolutely intolerable. And so you raise the threshold for a conviction so high that you can virtually guarantee that no innocent person will be wrongly executed. Of course, in doing so, it’s likely that a few real murderers will get away.

This simple lesson in statistical decision theory makes an important point. The probability of Type I and Type II errors are related. You decide which is more important to you and set the thresholds accordingly. There are always risks of errors occurring when you make decisions based on incomplete information. You simply have to decide which of the two kinds of mistakes will be better tolerated. I have many middle-aged male friends who debate the merits of a PSA test for prostate cancer. The test almost never misses an actual case of the disease, but it is notorious for false positives. As a potential victim of the disease, would you want to be sure that nothing life threatening has slipped by undetected, even if it means worrying needlessly after being told about a condition you actually didn’t have?

Natural selection of the human perceptual system faced these issues quite some time ago, and it is clear which approach to the Type I versus Type II errors it took. Imagine the following scenario. One of your ancestors is walking through the forest and sees something on the path ahead. It might be a predator. Then again, it might be a random array of shapes and textures amounting to nothing. If he believes it to be dangerous, he takes the appropriate defensive steps. Perhaps he freezes or arms himself or flees. What’s the best that can happen? He survives a lethal encounter and gets to live and function another day. What’s the worst? A false positive. He finds himself with heart pounding, pulse racing, hiding behind a tree with a spear drawn for no good reason. It was only a pile of twigs on the path. He’s wasted some effort and experienced a baseless fear. But he gets to go home, eat dinner, and snuggle with his mate. Maybe he’s even got a good story to tell, if such things were part of hominin social life.

Now consider an alternative scenario. The same individual sees something ahead that might or might not constitute a threat. Rather than assume the worst and squander some autonomic arousal, his perceptual system does not integrate the shapes and register the pattern as a threat. The best that can happen? He saves some calories, does not flee or freeze needlessly, and can boast a perceptual system more finely attuned to physical realities around him. The worst that can happen? A false negative, or Type II error. By not interpreting those stimuli as a threat, he fails to flee. Type II errors in this context are probably fatal. This hypothetical hominin is less likely to become anybody’s ancestor.