Irrationality Book Summary - Irrationality Book explained in key points

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Irrationality summary

Name: Irrationality
Rating: 4.3 (70 reviews)
Author: Stuart Sutherland

Stuart Sutherland

The Enemy Within

4.3 (70 ratings)

23 mins

Brief summary

Irrationality by Stuart Sutherland explores how human behavior defies rationality despite our belief that we are objective. It reveals how cognitive biases, emotions, and social pressures influence our decisions, leading to flawed thinking and irrational behavior.

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Table of Contents

Irrationality
Summary of 10 key ideas

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Key idea 1 of 10

What’s in it for me? Find out about your own irrationality.

Human beings are rational beings. Since the Enlightenment in eighteenth-century Europe, this simple fact has been a central assumption of scholars and thinkers and continues to be something we are taught from an early age.

But are we really as rational as we think?

Well, we’re actually far less rational in our daily behavior than we might suspect. Whether it’s when we judge other people by their looks, when we feel we should follow our intuition or when we refuse to change our minds even though it flies in the face of reason, irrationality is part of our daily routine, and it often goes completely unnoticed.

These blinks will show you what irrationality entails, how we are irrational in many situations and what we can do to become more rational.

You’ll also learn

why we think good-looking people are intelligent;
how peer pressure can derail rational thinking; and
why eighteenth-century people thought that turmeric cured jaundice.

Irrationality is more common than people think, and it’s the result of ignoring knowledge.

We tend to think that human beings are deeply rational beings, and the basis for this idea can be traced back thousands of years. From Aristotle’s claim that man is a “rational animal,” to Descartes’ famous statement, “I think, therefore I am,” to Kant’s “have the courage to use your own reason,” a common belief throughout history has been that humans are fundamentally rational.

But this might not be true after all.

When we meet a new person, we often judge them in an instant, based solely on their looks. This is both exceedingly common and totally irrational, as people often turn out to behave very differently than they appear.

So, clearly we’re prone to irrationality – but what does that word actually mean?

In a nutshell, irrationality means deliberately forming conclusions that aren’t based on knowledge. So, it might be rational for a young boy to climb a tree to try to touch the moon. But the same action would be absolutely irrational if performed by an adult astronomer who knows how far away the moon is.

Basically, the breadth of our knowledge plays a role in determining the rationality of our actions. But, while rational thinking is based on knowledge, rational conclusions can also be false. For example, people long believed that all swans were white; this was a completely rational assumption until the Australian continent was discovered, where black swans are common.

This is an example of how insufficient or false knowledge can produce false conclusions, despite rational thinking. But false rationality is not to be confused with irrationality. Irrational thinking differs in the sense that it’s deliberate.

Inadvertently forgetting to carry the one when doing math will produce an error – but it wouldn’t be the result of irrationality. Irrationality would be to ignore knowledge despite its ample presence, such as by thinking someone is unsuited for a job despite her résumé being a perfect fit for the requirements.

So, making an irrational decision requires deliberate action. But why do humans do this?

Irrationality affects individuals and organizations alike.

People make irrational decisions for a variety of reasons, and this tendency plagues both individuals and major organizations. In the case of individuals, people tend to distort their sense of reality in order to maintain irrational behavior and thoughts.

After making a decision, we often glorify our choice because we don’t want to admit the possibility of being wrong. Likewise, we tend to lower our opinion of the option we didn’t choose.

When and how we receive information is a major factor in our irrationality.

As you might know, you’re much more likely to be killed in a car accident than by a shark attack while swimming in the ocean. Even so, the 1975 movie premiere of Jaws, a film about a man-eating shark, caused a sharp drop in sea swimmers in California.

The frightened Californians were succumbing to something known as the availability error, wherein people irrationally ignore known facts and pay attention to information that makes the biggest impression on them, or that comes to mind most easily. In other words, what’s most directly “available.”

Doing what is socially expected and publicly announcing decisions can lead to irrational behavior.

Conforming to social norms is often one of the most rational things you can do. For instance, it’s rational to conform to driving on the correct side of the street to avoid a car accident. But conforming to social norms can also produce irrational behavior.

For example, the psychologist Solomon Asch demonstrated that subjects make irrational choices simply to conform to what society expects. He did so by showing his test subjects two cards: the first one had one line on it and the second had the same line as well as two others, one considerably longer and the other shorter than the first line.

Giving rewards is irrational and being deprived of choice spurs irrational behavior.

We all love rewards, and it might seem like giving them is a rational form of encouragement. But the exact opposite is true: while verbal praise might be a good motivator, since it can be internalized by the recipient and keep encouraging them for times to come, physical rewards are actually quite discouraging. In fact, rewards don’t actually make people perform better at all, and giving them is thus totally irrational.

In one experiment with students, the participants were asked to write headlines for their college newspaper. One group was paid while the other was not. In the end, the unpaid students wrote more headlines, showing that the incentive of a monetary reward produces worse performances.

Denying information to maintain beliefs, as well as our emotions, can make us act irrationally.

It’s common for logic to be juxtaposed with emotions, and it’s thus of little surprise that the latter are strongly tied to irrational behavior. For instance, we might love our partner so much that we believe she’s the greatest person on the planet, or might avoid doctors because we’re terrified of finding out we’re sick. In short, emotions make us behave irrationally because they distort our worldview.

But emotions are different than feelings. We might feel cold or tired; on the other hand, emotions are a combination of certain feelings with our tendency to act and think in certain ways.

Irrationality prevents us from properly assessing correlations and cause-and-effect relationships.

It wasn’t long ago that scientists couldn’t show a correlation between smoking and lung cancer. In fact, the connection between the two went unnoticed for centuries before the scientists Richard Doll and Richard Peto released certain statistics in the 1970s.

So, why did people fail to make this connection?

Overconfidence and intuition lead to irrational decisions.

Whether the task at hand is properly assessing the size of a parking space, the time needed to boil an egg or the strengths of a prospective hire, our intuition can often prove incorrect. We tend to be overly confident in our judgments and our own gut feelings.

For instance, one study found that people who were 100 percent sure of their ability to spell certain words, actually only spelled 80 percent of them correctly. Another survey found that 95 percent of British drivers believed they were better than the average motorist, while most people think they’ll live longer than the average person.

Knowledge of statistics improves rationality.

So, you’ve seen how people are irrational in a variety of ways; but is rationality really so desirable?

Well, the truth is, being rational isn’t as important in the personal realm since your personal choices, like whether to have pasta or rice for dinner, aren’t especially important. And when they are more important, like when choosing a career, there are so many unknown factors that rationality only marginally increases the likelihood of a successful outcome.

Avoid irrationality by paying attention to the way questions are phrased and writing out pros and cons when making decisions.

While an understanding of statistics might help you make more rational decisions, especially when it comes to serious and complicated issues, it’s impractical to spend loads of time making calculations. So, here are some simpler ways to avoid irrationality.

One way is to know that the way a question is phrased can irrationally influence your response. For example, in one study, certain subjects were asked whether they’d rather save 200 people from an imaginary lethal disease, or attempt to save 600 people with a 33 percent likelihood of success. Another group was asked to choose between the risk of letting 600 people die with a probability of 67 percent that they would die, or letting 400 people die for sure.

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What is Irrationality about?

Irrationality (1991) is a guide to illogical decisions, unreasonable actions and irrational behavior as a whole. These blinks reveal how people tend to be more irrational than rational, examines several reasons why and offers solutions as to how we can become a little more logical in our decision making.

Best quote from Irrationality

Everybody is irrational some of the time, and the more complex the decisions to be taken, the more irrational they are.

—Stuart Sutherland

Who should read Irrationality?

People who think of themselves as entirely rational beings
Anyone who struggles to make decisions, especially rational ones

About the Author

Stuart Sutherland was a renowned psychologist and writer who taught at Oxford University and the University of Sussex. He is best known for his book Irrationality and a personal account of his struggle with manic depression, titled Breakdown.

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