I've read 285 books in the past four years. Some were awful. Others were incredible. But I took notes on all of them.

I've never known what to do with these notes. Then I got an idea: I'll dump some of the highlights into a weekly article.

Mistakes Were Made (but Not by Me) by Elliot Aronson and Carol Tavris is a fantastic read about cognitive dissonance: the inability to hold two conflicting ideas in your head at the same time. Here are six things I learned from the book. 

1. Everyone wants to be right and hates admitting the possibility of being wrong.

As fallible human beings, all of us share the impulse to justify ourselves and avoid taking responsibility for any actions that turn out to be harmful, immoral, or stupid. Most of us will never be in a position to make decisions affecting the lives and deaths of millions of people, but whether the consequences of our mistakes are trivial or tragic, on a small scale or a national canvas, most of us find it difficult, if not impossible, to say, "I was wrong; I made a terrible mistake."

The higher the stakes -- emotional, financial, moral -- the greater the difficulty. It goes further than that: Most people, when directly confronted by evidence that they are wrong, do not change their point of view or course of action but justify it even more tenaciously. Even irrefutable evidence is rarely enough to pierce the mental armor of self-justification.

2. You brain is designed to shut out conflicting information.

In a study of people who were being monitored by magnetic resonance imaging (MRI) while they were trying to process dissonant or consonant information about George Bush or John Kerry, Drew Westen and his colleagues found that the reasoning areas of the brain virtually shut down when participants were confronted with dissonant information, and the emotion circuits of the brain lit up happily when consonance was restored. These mechanisms provide a neurological basis for the observation that once our minds are made up, it is hard to change them.

3. The higher the stakes, the harder it is to think clearly.

The racetrack is an ideal place to study irrevocability, because once you've placed your bet, you can't go back and tell the nice man behind the window you've changed your mind. In this study, the researchers simply intercepted people who were standing in line to place two-dollar bets and other people who had just left the window. The investigators asked everyone how certain they were that their horses would win. The bettors who had placed their bets were far more certain about their choice than were the folks waiting in line. But, of course, nothing had changed except the finality of placing the bet. People become more certain they are right about something they just did if they can't undo it.

4. Experience doesn't help you think better. It might actually hurt.

Hundreds of studies have shown that predictions based on an expert's "personal experience" or "years of training" are rarely better than chance, in contrast to predictions based on actuarial data. But when experts are wrong, the centerpiece of their professional identity is threatened. Therefore, as dissonance theory would predict, the more self-confident and famous they are, the less likely they will be to admit mistakes. And that is just what Tetlock found. Experts reduce the dissonance caused by their failed forecasts by coming up with explanations of why they would have been right "if only" -- if only that improbable calamity had not intervened; if only the timing of events had been different; if only blah blah blah.

5. You are twice as biased as you think you are.

The brain is designed with blind spots, optical and psychological, and one of its cleverest tricks is to confer on us the comforting delusion that we, personally, do not have any. In a sense, dissonance theory is a theory of blind spots -- of how and why people unintentionally blind themselves so that they fail to notice vital events and information that might make them question their behavior or their convictions. Along with the confirmation bias, the brain comes packaged with other self-serving habits that allow us to justify our own perceptions and beliefs as being accurate, realistic, and unbiased.

Social psychologist Lee Ross calls this phenomenon "naive realism," the inescapable conviction that we perceive objects and events clearly, "as they really are." We assume that other reasonable people see things the same way we do. If they disagree with us, they obviously aren't seeing clearly. Naive realism creates a logical labyrinth because it presupposes two things: One, people who are open-minded and fair ought to agree with a reasonable opinion. And two, any opinion I hold must be reasonable; if it weren't, I wouldn't hold it. Therefore, if I can just get my opponents to sit down here and listen to me, so I can tell them how things really are, they will agree with me. And if they don't, it must be because they are biased.

6. How we view others' opinions is totally skewed.

Ross and his colleagues have found that we believe our own judgments are less biased and more independent than those of others partly because we rely on introspection to tell us what we are thinking and feeling, but we have no way of knowing what others are really thinking. And when we introspect, looking into our souls and hearts, the need to avoid dissonance assures us that we have only the best and most honorable of motives. We take our own involvement in an issue as a source of accuracy and enlightenment -- "I've felt strongly about gun control for years; therefore, I know what I'm talking about" -- but we regard such personal feelings on the part of others who hold different views as a source of bias -- "She can't possibly be impartial about gun control because she's felt strongly about it for years."

Go and buy the book here. It's great. 

Contact Morgan Housel at mhousel@fool.com. The Motley Fool has a disclosure policy.