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WE LIKE TO think that we’re totally logical when we make decisions and arguments.

But over the past few decades, social science has uncovered a staggering number of cognitive biases that shape our thinking and behaviour – whether we know it or not.

Ever blamed someone else’s character for their mistakes, but blamed our circumstances for our own? There’s a name for that.

Did you have a granny who smoked 40 a day, and lived to 100? If you think that means smoking is harmless, there’s a name for that error.

Here are some of the major cognitive biases that are poisoning your mind.

Affect heuristic

The way you feel affects the way you interpret the world.

Let’s say the words “rake,” “take,” and “cake” flash in front of you for a split second.

If you’re hungry, all you see is CAKE.

Availability heuristic

Steven Ritzer Steven Ritzer

When you overestimate the importance of information, because it’s available to you.

For example, you might argue that smoking is not unhealthy, because your granddad smoked 40 a day, and lived to 100.

Bandwagon effect

Most of us are aware of this one. The probability of one person adopting a belief increases based on the number of people who hold that belief.

This is a powerful form of “groupthink.”

Clustering illusion

The tendency to see patterns in random events.

Often seen in gambling fallacies – like the idea that red is more (or less) likely to show up on a roulette wheel, after a series of reds.

Confirmation bias

This is a huge one, and central to so much of our news reading (and sharing) habits.

We tend to pay attention only to information that confirms our preconceptions, regardless of whether that information is actually true.

Decoy effect

Acarlos1000 Acarlos1000

Businesses have very sneakily taken advantage of this tendency.

If you sell two sizes of coffee – small and large – people are more likely to buy the small one.

Add a third, even larger option, though, and people will go for the one in the middle – which is now the medium option.

Frequency illusion

A friend just told you the name of a great, obscure band, and sent you some of their music.

Suddenly, you’re seeing and hearing them absolutely everywhere. Spooky.

Or not. You’re just subconsciously looking out for it, now that you have a name for it.

Fundamental attribution error

One of the most important, and prevalent biases out there.

This is where you attribute someone’s behaviour to an intrinsic quality of their identity, rather than the situation they’re in.

You might think your new colleague is a horrible, fundamentally angry person, but the truth is – they stubbed their toe earlier on today.

Self-fulfilling prophecy

Also called the “Galatea effect” – this is a bias in our thinking that can have real consequences – especially in educational achievement.

If you’re expected to succeed, it sets in motion a series of events that make you more likely to succeed.

Best summed up by Henry Ford’s great maxim: “Whether you think you can or think you can’t, you’re right.”

The Halo effect

If you have a positive, overall impression of someone – you’re likely to attribute all sorts of great qualities to them, that they may not have.

Physical attractiveness plays a huge part in the Halo effect. If someone’s good-looking, we are inordinately likely to think of them as trustworthy and intelligent as well, even if we’ve never said so much as “Hello” to them.

Celebrity endorsements are based on this bias. Johnny Sexton is an outstanding professional rugby player and absolute hero to so many of us. But does that mean you’d take his financial advice?

Hyperbolic discounting

I can give you €10 now. Or €11 tomorrow. Which do you choose?

Objectively, the rational, sensible thing to do is hang on for 24 hours, and take the larger amount.

But our tendency to take an immediate payoff rather than a larger gain, later, means most of us would take the €10 now.

Illusion of control

If you’ve ever had to put up with someone screaming at a football team through the TV, you’re already an expert in this cognitive bias.

The tendency for people to overestimate their ability to control events can get really stupid.

For example, people who want a high number will roll the dice harder, and roll the dice more softly if they want a low number. Neither has any actual effect.

Negativity bias

The tendency to emphasise bad experiences over good ones, and perceive threats rather than opportunities, can be crippling.

But some psychologists would argue that it was an evolutionary necessity – it’s better to mistake a rock for a bear, than a bear for a rock.

Omission bias

This is a really interesting one, and at the heart of a few moral conundrums.

We tend to condemn action more than inaction, even if the results are the same.

Here’s the final fight between Batman and Ra’s al Ghul in Batman Begins. (Starts 1.12).

“I won’t kill you – but I don’t have to save you,” says Batman, as he escapes from a train hurtling off the tracks.

The end result – death – is the exact same, but the Caped Crusader satisfies his conscience by engaging in some blockbuster omission bias.

Outcome bias

Evaluating a decision based on how it turned out, rather than how the decision was made.

Let’s say all the forecasts are predicting a hurricane, and the storm clouds are starting to gather. You decide to go for a bike ride along the coast.

If the hurricane misses, and you end your bike ride invigorated and still alive, you didn’t make a good decision, you were just really, really lucky.

As the adage goes, “A broken clock is right twice a day.”

Post-purchase rationalisation

T.Phipps Photography T.Phipps Photography

When you convince yourself that 64 inch ultra-HD smart TV was excellent value for money.

This one raises the important issue of “cognitive dissonance” – an upsetting conflict between your thoughts and actions, or what you’d like to believe about something, and the reality of it.

When you impulsively buy something dear, what follows is known as “buyer’s remorse.”

It’s upsetting, and you have to get rid of it somehow – otherwise you could never bring yourself to actually drive that luxury car you know you couldn’t afford.

Hence post-purchase rationalisation. You dream up a million and one reasons why buying the TV was the best decision you’ve ever made, just so you can ease the cognitive dissonance.

Reactance

The desire to do the opposite of what someone wants you to, purely because you feel your freedom to choose in under threat – even if, objectively, what they want you to do is in your best interests.

Hi, teenagers.

Survivorship bias

An error that comes from focusing only on surviving, easily visible examples.

For instance, we might think that being entrepreneur is easy because we haven’t heard of all of the entrepreneurs who have failed. (See also: actors, rock stars, professional athletes).

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