April 21, 2022
 min read

Mind Macros 13: The availability heuristic, Bayesian reasoning, and identity capital

Table of Contents

Table of Contents

Hello, friend.

Welcome to another issue of Mind Macros - I hope you find something of value.

Food for Thought

1. The availability heuristic

"People judge the probability of events by the ease with which instances come into mind, a habit that Tversky and Kahneman called the Availability Heuristic. We use the ranking from our brain's search engine—the images, anecdotes, and mental videos it coughs up—as our best guess of the probabilities. The heuristic exploits a feature of human memory, namely that recall is affected by frequency: the more often we encounter something, the stronger the trace it leaves in our brains."

"The availability bias may affect the fate of the planet. Several eminent climate scientists, having crunched the numbers, warn that 'there is no credible path to climate stabilization that does not include a substantial role for nuclear power.' Nuclear power is the safest form of energy humanity has ever used. Mining accidents, hydroelectric dam failures, natural gas explosions, and oil train crashes all kill people, sometimes in large numbers, and smoke from burning coal kills them in enormous numbers, more than half a million per year. Yet nuclear power has stalled for decades in the United States and is being pushed back in Europe, often replaced by dirty and dangerous coal. In large part the opposition is driven by memories of three accidents: Three Mile Island in 1979, which killed no one; Fukushima in 2011, which killed one worker years later (the other deaths were caused by the tsunami and from a panicked evacuation); and the Soviet-bungled Chernobyl in 1986, which killed 31 in the accident and perhaps several thousand from cancer, around the same number killed by coal emissions every day." — From Rationality by Steven Pinker

The media has amplified our irrational judgments. One classic example is the safety of flying versus driving. Unless a celebrity is behind the wheel, car accidents rarely make the news. In contrast, plane accidents receive heavy coverage, even if the pilot makes a safe landing.

The world's roads account for 1.3 million fatal accidents each year, while plane crashes kill 250 people. According to Pinker, planes are about a thousand times safer per passenger mile than cars, yet we all know people who fear flying but no one with a fear of driving. These irrational fears arise from the media's availability bias, since news is what happens, not what doesn't.

We hear about the single plane crash of the year, but not about the 364 days of safe air travel. To put it another way, if news outlets used the same approach with cars, they would have to run the headline, "35,000 dead in road accidents today," every single day.

"As the economist Max Roser points out, news sites could have run the headline 137,000 PEOPLE ESCAPED EXTREME POVERTY YESTERDAY every day for the past twenty-five years. But they never ran the headline, because there was never a Thursday in October in which it suddenly happened. So one of the greatest developments in human history—a billion and a quarter people escaping from squalor—has gone unnoticed." — Steven Pinker

2. The law of the excluded middle

"The law of the excluded middle requires that a thing must either possess a given attribute or must not possess it. A thing must be one way or the other; there is no middle. In other words, the middle ground is excluded. A shape either is a circle or is not a circle. A figure either is a square or is not a square. Two lines in a plane either intersect or do not intersect. A statement is either true or not true. However, we frequently see this principle misused.

"How many times have you heard an argument (intentionally?) exclude the middle position when indeed there is a middle ground? Either you're with me or you're against me. Either you favor assisted suicide or you favor people suffering a lingering death. America, love it or leave it. These are not instances of the excluded middle; in a proper statement of the excluded middle, there is no in-between. Politicians frequently word their arguments as if the middle is excluded, forcing their opponents into positions they do not hold." — From Logic Made Easy by Deborah J. Bennett

Aristotle established the law of the excluded middle, a rule of logic that states that any proposition is true, or its negation is true.

The misuse of the logical principle looks like this: If you are not X, you're against X.

The law of the excluded middle is a convenient trick for constructing arguments based on half-truths and deliberate deception. Be aware of it when engaging people or assessing the legitimacy of debaters.

As Bennett notes in the passage above, we are discussing the popular misuse of this principle. Those who misuse the principle will intentionally exclude the middle ground, whereas the logical principle states that there is no middle ground to begin with.

Practical Advice

1. Bayesian reasoning

"Bayes' rule or Bayes' Theorem is the law of probability governing the strength of evidence—the rule saying how much to revise our probabilities (change our minds) when we learn a new fact or observe new evidence.

"A paradigm case of Bayesian reasoning is medical diagnosis. Suppose that the prevalence of breast cancer in the population of women is 1 percent. Suppose that the sensitivity of a breast cancer test (its true-positive rate) is 90 percent. Suppose that its false-positive rate is 9 percent. A woman tests positive. What is the chance that she has the disease? The most popular answer from a sample of doctors given these numbers ranged from 80 to 90 percent. Bayes's rule allows you to calculate the correct answer: 9 percent. That's right, the professionals whom we entrust with our lives flub the basic task of interpreting a medical test, and not by a little bit. They think there's almost a 90 percent chance she has cancer, whereas in reality there's a 90 percent chance she doesn't. Imagine your emotional reaction upon hearing one figure or the other, and consider how you would weigh your options in response. That's why you, a human being, want to learn about Bayes's theorem." — From Rationality by Steven Pinker

Imagine we believe ourselves to be a safe driver who, one day, gets into a car accident. Can we reconcile the accident with our belief that we're a competent driver? Yes, it's the other driver's fault! By doing this, we retain the positive beliefs about our driving ability instead of updating them in response to the evidence.

With Bayes' theorem, we can ask if this evidence is more consistent with our current belief system or with another.

Do you think the car accident is more likely to have happened if you were a good driver or a bad one?

Being a responsible driver is still possible after a car accident. We're not using the law of the excluded middle here. Imagine beliefs as a sliding scale of probabilities. The level of confidence in our driving ability may drop from 80% to 60% after the crash.

But why should the evidence alter our beliefs at all? Because the accident is less likely to have happened if we are a responsible driver than if we're not. This ability to update our beliefs based on the latest evidence is Bayes' theorem at work. [1]

Probabilistic thinking means avoiding absolutes. When we express the likelihoods of our beliefs, we open the door to further discussions. Rather than expressing things in black and white terms, as true or false, try saying: 'I'm an 80 on that', or 'I'm only a 25 on that'. As a result, we remain receptive to new evidence while gathering information to guide future truth-seeking efforts.

2. Identity capital

"Identity capital is our collection of personal assets. It is the repertoire of individual resources that we assemble over time. These are the investments we make in ourselves, the things we do well enough, or long enough, that they become a part of who we are. Some identity capital goes on a résumé, such as degrees, jobs, test scores, and clubs. Other identity capital is more personal, such as how we speak, where we are from, how we solve problems, how we look. Identity capital is how we build ourselves—bit by bit, over time. Most important, identity capital is what we bring to the adult marketplace. It is the currency we use to metaphorically purchase jobs and relationships and other things we want." — From The Defining Decade by Meg Jay

We are our own assets. Our ability to take advantage of opportunities grows as we expand our circle of competence. By preparing for opportunities, we can generate our own luck.

Let's imagine two young entrepreneurs.

Lucy begins to build her identity capital by attending events, studying courses, and reading biographies of her favorite leaders.

Mark believes he doesn't require help, watches productivity YouTubers as a form of procrastination, and changes his business plan every week.

Who is most likely to succeed?

Lucy is preparing for opportunities by building her identity capital. Even if Mark stumbles upon a similar opportunity, his lack of preparation prevents him from taking advantage. Lucy is said to be lucky and Mark unlucky, but luck happens when preparation meets opportunity.

The lesson? Always choose the option that offers the most optionality to maximize your chances of getting lucky.

Quotes to Ponder

1. Anne Lamott on the importance of resetting ourselves:

"Almost everything will work again if you unplug it for a few minutes, including you."

2. Richard Feynman on the ease in which we mislead ourselves:

"The first principle is that you must not fool yourself—and you are the easiest person to fool."

​Thank you for reading,

Matthew Vere


[1]. The driving example comes from Julia Galef's excellent video on Bayes' Rule.

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