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Why Your Mind Isn’t Rational All the Time

Certain cognitive biases that make us better at surviving harsh environmental conditions also cause us to make irrational decisions, from betting against the odds to rationalizing wrong decisions. 
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Humans are famously irrational, from betting against the odds to rationalizing wrong decisions. It turns out our brains may be hardwired to commit certain errors, but knowing what those errors are can help us avoid them. Confirmation bias attracts us to opinions that are the same as ours, making us feel correct but shielding us from important information that may counter our own biases. Ingroup bias causes us to overestimate the abilities of our circle of friends at the expense of people we don’t know. Post-purchase rationalization occurs when we justify a frivolous expense by inventing a dubious reason for having spent money. 

What’s the Big Idea?

Why is our reasoning faculty strong enough to point out our errors yet too weak to affect a permanent change in behavior? Strong evolutionary forces may be behind our irrational decisions, say scientists, who have noted the importance of forging tight inter-group bonds, for example, in order to survive harsh environmental conditions. Negativity bias causes us to consider the most horrific events in the day’s newspaper as more important, even though good or benign events are far more common. The reason, according to evolutionary psychology, is that we need to stay abreast of threats to our health and well-being. 

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