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Dudley Dowell
common sense
scientific consensus
Thu, Apr 23, 2015 - 12:00 AM

What's wrong with using my own brain and common sense in deciding what scientific conclusions I want to accept or not?

1 Answer


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Bo Bennett, PhD
Host, Doctor of Social Psychology


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Bo Bennett, PhD

Host, Doctor of Social Psychology


About Bo Bennett, PhD

I am the host of this show :) For my complete bio, please see
PrintThu, Apr 23, 2015 - 12:00 AM

Let me start by being perfectly clear that we should always employ reasoning when it comes to making decisions that matter. However, an important part of the reasoning process is knowing when to defer to those who know more than you on a particular issue, especially when "common sense" is anything but common, and often in conflict with reality. Further, personal freedoms to reject the scientific consensus on certain issues can have a devastating impact on others. For these reasons and more, understanding the full answer to this question is extremely important.

"Common Sense" and "Intuitions" Often Contradict Reality

What is generally referred to as "common sense" is a subjective sense of our own knowledge. In psychology, there is a phenomenon known as the Dunning-Kruger Effect, which is the illusion that we are smarter than we actually are based on the fact we lack the cognitive capacity to realize our own ineptitude. In fact, this is only one of the hundreds of known cognitive biases that virtually assure that our perception of reality is greatly skewed and often incorrect.

From an evolutionary perspective, these biases are a result of helping us pass on our genes. Evolution does not care if we are smart, logical, reasonable, rational, or even right—as long as our intuitions and "common sense" are more conducive to passing on our genes than they are hindrance to that goal. The accurate information we do have as a result of the non-conscious and non-deliberate processes is obtained partly by genetics and partly by our environment. For example, it is "common sense" that we don't want to jump off a cliff because our ancestors had a healthy fear of doing so... that is why they lived long enough to pass on their genes. It is "common sense" for us to look both ways before crossing a road not because of our primate ancestors, but because of learning in our current environment. Be careful not to associate all evolutionary tendencies with good common sense. For example, eating as much as you can at every opportunity might have helped our ancestors survive, but this tendency is sending us to our graves early.

Here are just some examples where "common sense," "gut-feelings," "intuitions," and "our own understanding" are clearly at odds with reality:

common sense tells us that the earth is flat (it's not)

common sense tells us the earth is the center of the universe (it's not)

common sense tells us the objects are solid (they are actually 99.9999999999999% empty space)

common sense tells us that heavier objects drop faster than light ones (they don't)

common sense tells us that if we flip a fair coin 5 times in a row and it comes up head, then tails is "due" (it's not)

common sense tells us that the winning lottery numbers "23, 5, 14, 34, 8, 38" are far more likely than "1, 2, 3, 4, 5, 6" (it's not)

common sense tells us that an airplane is too heavy to fly (it's not)

common sense tells us that time passes at the same rate everywhere (it doesn't)

... and virtually everything related to quantum mechanics, the most well-supported scientific theory every developed, is against common sense

It would be nice if we can just "know" things magically. In fact, the appeal to common sense is often based on a combination of laziness and a defense of our own intellectual limitations. The pain of not knowing something is reduced by simply thinking we know—and not just know but know better than those who spend their lives doing the work to really find out.

Experts and Trust

There is a clear relationship between ignoring the claims of experts in favor of your own "common sense" and trust. If we were to undergo brain surgery, very few of us would question the surgeon's technique and choice of surgical instruments. Why? Our level of trust in the surgeon is high, and our level of confidence in our own understanding of the topic is very low. But what if the Internet was full of websites claiming that brain surgery was a conspiracy, and just a surgeon's way of separating you from your money. No matter how full of crap these sites were, you may be persuaded by their strong emotional appeals, anecdotes, and cherry-picked data. You would be under the illusion that your level of "knowledge" on the topic is strong, and conversely, your level of trust in the surgeon would drop, to your own, and often society's detriment.

Here are some things to keep in mind to prevent this intellectually dangerous downward spiral.

Don't think that reading a few articles on the Internet makes you more qualified than a scientist who spent 6+ years studying the topic and many more researching.

Realize that conspiracies are a lot less common than you think. Watch this excellent two-part video on conspiracies from my friend Dr. Kevin deLapante.

Don't trust people, trust the science. Separate the message from the messenger. Look at the sources and give more weight to meta-analyses that combine sometimes hundreds of studies into one.

Ask yourself if your views on the issue are politically motivated. The scientific conclusions are sometimes politically incorrect and provide evidence against the claims and positions of your political party. But science does not care about your politics, and neither should you when it comes to separating fact from fiction.

Your "Freedom to Reject Science" Ends When It Puts the Safety and Lives of Others in Jeopardy.

Discussing freedom is a touchy issue, but it is important in understanding that your "right" to reject certain findings in science is limited, just as your "right" to freedom of speech is limited by not yelling "bomb" in an airport. Some examples include:

Rejecting the science behind the safety of vaccines and putting your own children, and other people who cannot get vaccines at risk.

Lobbying against GMOs "because it just seems wrong" rather than understanding the science behind GMOs, not realizing that GMOs can save millions of lives of people who are starving and cannot afford to shop at Whole Foods.

Insisting that the universe is 6000 years old and trying to have that idea taught in public schools, which is undermining the younger generation's trust in science.

Use your own brain—but know its limits. We are all subject to cognitive biases that give us a false sense of confidence in what we think we know and rationalize that the easy way out (expending no cognitive energy) gives us the intellectually superior high ground, when it clearly does not.
Bo Bennett, PhD
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Podcast Episode: The Problem with Relying on Your Own Common Sense and Ignoring Scientific Consensus

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Thursday, April 30, 2015 - 06:22:11 PM
I gotta tell you, I disagree with Dr. Bo on this and hate his answer. It's full of tired examples of things that don't really define common sense. For example, common sense does not tell us the world is flat. Scientists of the time told us the world was flat. And so it seemed. But it wasn't "common sense" that made people believe it at the time it was 'general consensus' and if i'm a woman living in the 1500's and my husband tells me the world is flat, then great- can I go fetch the well water, tend to the sick baby, suckle my 3 year old, and go hunt a rodent for tonights dinner now? Same with your 'earth is the center of the universe' example. Bad. This is not what common sense is.These aren't common at all. In fact, there is not one example you gave that qualify as common. As a mother of 3 teenagers, I have numorouse examples of common sense- or lack there of. But first, its not that common sense contridicts reality, it's that its overrided by a few things that trump it. For instance, perhaps the first real example of common sense ever used on earth might have been by neanderthals playing with fire. "Fire goood" "Fire Hot!" "I see what fire do to trees and Mammouth" "Me wanna touch fire anyway". Common Sense overridden by: Curiosity.
Some other examples; You have a big paper due for school. You procrastinate. Common sense tells you to work on it, but Kim Kardashian is balancing a champagne glass on her ass on the internet and you need to tweet about it. Common sense tells you your wasting time but you wait until the morning its due to complete it, making the paper worthy of a "D" -not your best work. #CommonSenseOverridden: Lazyness
You go to buy a car froma guy on Criagslist. The cars engine is smoking. Fluid leaking. Common sense tells you not to buy the car. But the car is a cherry red convertible. #CommonSenseOverridden by: Desire.
You meet a guy, divorced 3 times. He tells you coincidently, 2 of his ex-'s turned out to be lesbians and the 3rd cheated on him. All were nasty witches. Common sense tells you walk out the back exit, but his biceps, cheekbones and nice car tell you give him a shot. People can change. #CommonSenseOverridden: Desire/Lust/Financial gain.
You have gained 30lbs and have been dieting to try to loose the weight. Common sense tells you that you cannot eat the rest of that birthday cake that the kids didn't finish. #CommonSenseOverridden: Desire/Addiction.
You choose to vote for the woman for president, not based on the content of her character but based on her genitailia.You want to see the First woman President. #CommonSenseOverridden: Bias/Desire
Being 18 Billion Dollars in Debt. And ignoring it. #CommonSenseOverridden : Lazy/Apathetic

These are all things that require no "expert" intervention. This are "common" examples of when sense can be used or not.
The good news is you can hone your common sense by realizing when you should have used it but chose not to. Which is it that thawarted your path to making the right choice? Life is made up of choices and we need to rely on ourselves to grow confidently.
When you have gotten to this "expert level" of mastering common sense, by trial and error and by being a parent, then you need to be responsible and rely on common sense and intuition to keep your family safe and sound. You may not always be correct. But what is the alternative? Surrendering your judgement to a beauracrat or insurance company, or even a doctor ? A decent Dr. will admit "you know your body better that me" . I'm not talking about putting the general public at risk of measels or Polio. That is an extreme example. If you feel that strongly about not vaccinating because you consider 50+ years of vaccines still in the trail phase with unknown consequences, then homeschool your children. And by the way, if you are employing common sense, were YOU vaccinated?

I'm talking about statisics and data that cannot be relyed on like GMO's. Reguardless of tests and studies done by companies that stand to make or loose billions of dollars, if you are relying on common sense, ask yourself, do you want to be a part of an on going experiment with your health and the health of your family? The first Frankin Food tomato came on the market in 1994. Its recently become wide spread in the last 13 years. Not in European countrys mind you, just in America and the 3rd world countries who accept our cheap food. It's clearly an on going experiment. We might not know the consequences of eating and digesting foods that are designed to resist bugs and pests for generations. Until then I would appreciate it if foods were labeled so I could opt out of that experiment. I know seedless grapes are GMO. I eat them anyway. CommonSenseOverridden by: Convienience. But I know it. I don't buy them often, I prefer to drink my grapes. I know that's toxic to me. CommonSenseOverridden: Teenagers.

Raw milk was good for you, untill it was bad for you and now good for you once again. Tabbacco was good for you. Dr.s - experts - told Kennedy his 23 year old daughter's mood swings would be cured if he let them take out part of her brain in a new procedure called "Lobotomy" Common Sense overridden: Lack of Patience Living With Another Girl PMSing in The Kennedy Compound.
Yes we have come so far with science and access to published medical studies and sometimes you must trust an expert but only after your common sense tells you that you have investigated the issue enough an are full satisfied. Otherwise, in my opinion, your overriding the gift of Common Sense with: Laziness.

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