Quantum physics defies common sense, yet we see it work every day. The problem isn’t the physics, but our inadequate intuition, and we should follow the evidence. (More)

Common Sense Problems, Part III: When Evidence Defies Common Sense (Non-Cynical Saturday)

This week Morning Feature considers the problems with “common sense.” Thursday we began why many ideas are called “common sense” yet in fact are not both common and sensible. Yesterday we saw some ideas that are both common and sensible, yet are still false. Today we conclude with ideas that defy common sense, yet are still true.

“Can you hear me now?”

We’ve all seen those ads and experienced the quirky limits of cell phones. Yet we still rely on them and, most of the time, they work as we expect. The modern cell phone is an engineering marvel: a two-way radio and handheld computer more powerful than all of NASA’s computers, put together, when Apollo XI landed on the Moon.

And contrary to ‘UFO theorists,’ the technology for your cell phone was not given to us by extraterrestrials. The semiconductor transistor – the heart of your cell phone and all modern electronics – was invented in November and December of 1947 by AT&T engineers John Bardeen, Walter Brattain, and William Shockley, based on predictions they made using the equations of quantum physics. Yet as quantum physics pioneer and Nobel laureate Neils Bohr famously said, “Those who are not shocked when they first come across quantum theory cannot possibly have understood it.”

Modern physics legend Roger Penrose put it more plainly, saying “Quantum mechanics makes absolutely no sense.”

For example, quantum theory holds that the tiniest particles that make up everything in our universe are really waves. They exist as probability functions, possibly here or there, possibly this way or that, undetermined, until some other part of the universe needs to know something about them. At that moment, the waveform collapses and they are either here or there, either this way or that. Then they fuzz back into waves.

No, that doesn’t make sense. What’s more, quantum theory can’t predict whether a specific particle will be here or there, this way or that. The equations can only assign probabilities to each outcome. Yet those equations are arguably the most precisely tested theory in the history of science. And they work well enough that you’re reading this essay, on your computer or perhaps even on your cell phone. Still, the evidence supports a theory that defies common sense.

“Are we intuitive statisticians?”

The problem is not the theory, or the evidence. The problem is the limits of human intuition, and it’s not limited to quantum physics. In Thinking Fast and Slow, psychologist Daniel Kahneman writes that his exploration of what we now call decision theory and behavioral economics began with a simple question posed to colleague Amos Tversky: “Are we intuitive statisticians?”

Our intuition does many things very well, such as recognizing each others’ emotions or predicting the path of a ball as it flies through the air. Most humans understand stories and can predict how a story will end. Mystery novels play against and test our intuition as we try to guess “whodunit,” yet we expect mystery authors to play fair and follow certain rules. Authors debate the rules but authors and readers agree the ending must make sense … if only in that forehead-slapping “Oh now I get it!” way.

But our intuition did not evolve with an eye toward quantum theory, or even complex statistical calculations. Economists may derive optimal game theory strategies, but Humans are not Econs. And while most of us cherish freedom, sometimes we’re happier if we have fewer choices.

“Too much information!”

Most of us have said that, usually in jest after someone else reveals an embarrassing thought. But as a general rule, we think it’s better to gather as much information as we can, especially before we make an important decision. Online dating sites ask members to provide many personal details, yet they urge members to move slowly and learn more about each other before revealing a home address or meeting face-to-face. And for good reason.

Still, more information is not always better. If you go to an emergency room with chest pains, you should hope the doctor doesn’t ask about your age, weight, or family history. In fact, ER doctors correctly diagnose chest pain 70% more often if they have only an ECG and the answers to three questions – is the patient having unstable angina; is there fluid in the patient’s lungs; and is the patient’s systolic blood pressure below 100 – and plug those answers into a simple decision tree.

Getting more information such as age, weight, family history, tobacco use, diet and exercise habits – each of which seems relevant, intuitively – actually confuses the diagnosis. The evidence for that “less is more” cardiac diagnostic is overwhelming … yet it defies common sense.

“Follow the evidence”

Does this mean we should ignore common sense? That would probably be a bad idea, if it were even possible. We are what psychologist Jonathan Haidt calls an “ultrasocial species,” evolved to learn and cooperate largely by sharing intuitively sensible ideas or … common sense.

But when someone says “It’s just common sense,” we should pause to ask if that idea really is widely accepted and intuitively sensible, or if the phrase “commons sense” is being offered to lure us into following what may be an imaginary herd into what may be a senseless mistake. And even when an idea truly is common sense, we should recognize that’s not enough. It may still be false … and some important truths may defy our common sense.

In other words, we should look for evidence, and follow the evidence, especially on questions of public policy. That doesn’t guarantee we’ll be right, but it gives us the best probability we can get.


Happy Saturday!