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The Certainty Bias: A Potentially Dangerous Mental Flaw

A neurologist explains why you shouldn't believe in political candidates that sound too sure of themselves.
Robert Burton, former chief of neurology at the University of California at San Francisco-Mt. Zion hospital


Robert Burton is the former chief of neurology at the University of California at San Francisco-Mt. Zion hospital. He recently wrote a book, On Being Certain, that explored the neuroscience behind the feeling of certainty, or why we are so convinced we’re right even when we’re wrong. He and Jonah Lehrer, the editor of Mind Matters, discussed the science of certainty.

LEHRER: What first got you interested in studying the mental state of certainty?

BURTON: A personal confession: I have always been puzzled by those who seem utterly confident in their knowledge. Perhaps this is a constitutional defect on my part, but I seldom have the sense of knowing unequivocally that I am right. Consequently I have looked upon those who ooze self-confidence and certainty with a combination of envy and suspicion. At a professional level, I have long wondered why so many physicians will recommend unproven, even risky therapies simply because they "know" that these treatments work.

It is easy to be cynical and suspect the worst of motives, from greed to ignorance, but I have known many first-rate, highly concerned and seemingly well motivated physicians who, nevertheless, operate based upon gut feelings and personal beliefs even in the face of contrary scientific evidence. After years of rumination, it gradually dawned on me that there may be an underlying biological component to such behavior.

LEHRER: In your book, you compare the "feeling of certainty" that accompanies things such as religious fundamentalism to the feeling that occurs when we have a word on the-tip-of-our-tongue. Could you explain?

BURTON: There are two separate aspects of a thought, namely the actual thought, and an independent involuntary assessment of the accuracy of that thought.

To get a feeling for this separation, look at the Muller-Lyer optical illusion.

Even when we consciously know and can accurately determine that these two horizontal lines are the same length, we experience the simultaneous disquieting sensation that this thought—the lines are of equal length—is not correct. This isn't a feeling that we can easily overcome through logic and reason; it simply happens to us.

This sensation is a manifestation of a separate category of mental activity—-unconscious calculations as to the accuracy of any given thought. On the positive side, such feelings can vary from a modest sense of being right, such as understanding that Christmas falls on December 25, to a profound a-ha, "Eureka" or sense of a spiritual epiphany. William James referred to the latter—the mystical experience—as "felt knowledge," a mental sensation that isn't a thought, but feels like a thought.

Once we realize that the brain has very powerful inbuilt involuntary mechanisms for assessing unconscious cognitive activity, it is easy to see how it can send into consciousness a message that we know something that we can't presently recall—the modest tip-of-the-tongue feeling. At the other end of the spectrum would be the profound "feeling of knowing" that accompanies unconsciously held beliefs—a major component of the unshakeable attachment to fundamentalist beliefs—both religious and otherwise—such as belief in UFOs or false memories. 

LEHRER: Why do you think that the feeling of certainty feels so good?

BURTON: Stick brain electrodes in rat pleasure centers (the mesolimbic dopamine system primarily located in the upper brain stem). The rats continuously press the bar, to the exclusion of food and water, until they drop. In humans the same areas are activated with cocaine, amphetamines, alcohol, nicotine and gambling—to mention just a few behaviors to which one can become easily addicted.

It is quite likely that the same reward system provides the positive feedback necessary for us to learn and to continue wanting to learn. The pleasure of a thought is what propels us forward; imagine trying to write a novel or engage in a long-term scientific experiment without getting such rewards. Fortunately, the brain has provided us with a wide variety of subjective feelings of reward ranging from hunches, gut feelings, intuitions, suspicions that we are on the right track to a profound sense of certainty and utter conviction. And yes, these feelings are qualitatively as powerful as those involved in sex and gambling. One need only look at the self-satisfied smugness of a "know it all" to suspect that the feeling of certainty can approach the power of addiction.

LEHRER: To what extent do these mechanisms come into play during a presidential election? It seems like we all turn into such partisan hacks every four years, completely certain that our side is right.

BURTON: The present presidential debates and associated media commentary feel like laboratory confirmation that the involuntary feeling of certainty plays a greater role in decision-making than conscious contemplation and reason.

I suspect that retreat into absolute ideologies is accentuated during periods of confusion, lack of governmental direction, economic chaos and information overload. At bottom, we are pattern recognizers who seek escape from ambiguity and indecision. If a major brain function is to maintain mental homeostasis, it is understandable how stances of certainty can counteract anxiety and apprehension.  Even though I know better, I find myself somewhat reassured (albeit temporarily) by absolute comments such as, "the stock market always recovers," even when I realize that this may be only wishful thinking.

Sadly, my cynical side also suspects that political advisors use this knowledge of the biology of certainty to actively manipulate public opinion. Nuance is abandoned in favor of absolutes.

LEHRER: How can people avoid the certainty bias?

BURTON: I don't believe that we can avoid certainty bias, but we can mitigate its effect by becoming aware of how our mind assesses itself. As you may know from my book, I've taken strong exception to the popular notion that we can rely upon hunches and gut feelings as though they reflect the accuracy of a thought.

My hope is the converse; we need to recognize that the feelings of certainty and conviction are involuntary mental sensations, not logical conclusions. Intuitions, gut feelings and hunches are neither right nor wrong but tentative ideas that must then be submitted to empirical testing. If such testing isn't possible (such as in deciding whether or not to pull out of Iraq), then we must accept that any absolute stance is merely a personal vision, not a statement of fact.

Perhaps one of my favorite examples of how certainty is often misleading is the great mathematician Srinivasava Ramanujan. At his death, his notebook was filled with theorems that he was certain were correct. Some were subsequently proven correct; others turned out to be dead wrong. Ramanujan’s lines of reasoning lead to correct and incorrect answers, but he couldn’t tell the difference. Only the resultant theorems were testable.

In short, please run, do not walk, to the nearest exit when you hear so-called leaders being certain of any particular policy. Only in the absence of certainty can we have open-mindedness, mental flexibility and willingness to contemplate alternative ideas.

Are you a scientist? Have you recently read a peer-reviewed paper that you want to write about? Then contact Mind Matters editor Jonah Lehrer, the science writer behind the blog The Frontal Cortex and the book Proust Was a Neuroscientist.

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