Decision Making Bias: Availability

Learn about the Availability bias with exercises.

What is the Availability bias?

The concept in one sentence:

We overestimate the likelihood of events that are easier to recall.

The concept in one quote:

People tend to assess the relative importance of issues by the ease with which they are retrieved from memory—and this is largely determined by the extent of coverage in the media.

Daniel Kahneman

The benefit of being aware of the bias:

Be mindful that factors such as media coverage, vivid images, and ease of recall can cloud your judgment.


Example 1

If a random word is taken from an English text, is it more likely that the word starts with a K, or that K is the third letter?

  • Starts with a K

  • K is the third letter


K is the third letter.

It is easier to think of words that begin with "K", more than words with "K" as the third letter. Thus, people judge words beginning with a "K" to be a more common occurrence. In reality, however, a typical text contains twice as many words that have "K" as the third letter than "K" as the first letter.



Exercise 1

Which is more likely?

  • Dying from shark attacks

  • Dying from being hit by falling airplane parts

Exercise 2

According to the availability bias, which witness would be rated as more deceptive?

  • Witness A testified truthfully before lying.

  • Witness B was caught lying first before telling the truth.

Exercise 3

Which job is more dangerous?

  • Being a police officer

  • Being a logger (a person who cuts down trees for wood)

Exercise 4

Imagine the following scenarios: (a) A massive flood somewhere in America, in which more than 1,000 people die. (b) An earthquake in California, causing massive flooding in which more than 1,000 people die.

Which scenario is more likely?

  • Scenario (a)

  • Scenario (b)

Exercise 5

Rank the following causes of death in the United States (between 1990 and 2000) from most common to least common.

  1. Tobacco

  2. Poor diet and physical inactivity

  3. Motor vehicle accidents

  4. Firearms (guns)

  5. Illicit drug use

Exercise 6

Imagine two people competing for a promotion, one has done excellent work for the past 9 months, and the other has done extraordinary work for the past 3 months.

Who is more likely to get the promotion?

  • Excellent work for the past 9 months

  • Extraordinary work for the past 3 months

Exercise 7

In an experiment, two groups were asked to assess their own assertiveness. Group A was instructed to think of six examples that demonstrated their assertiveness—a fairly easy assignment. Group B was instructed to come up with twelve instances of their own assertiveness—a tougher task. 

After the exercise, which group felt more assertive?

  • Group A

  • Group B

Exercise 8

When are people more likely to purchase insurance to protect themselves from a natural disaster?

Exercise 9

How can a lottery company use the availability bias to increase sales of lottery tickets?


Answer to Exercise 1

Dying from being hit by falling airplane parts.

Many people think that the likelihood of dying from shark attacks is greater than that of dying from being hit by falling airplane parts when more people actually die from falling airplane parts. When a shark attack occurs, the deaths are widely reported in the media whereas deaths as a result of being hit by falling airplane parts are rarely reported in the media.


Answer to Exercise 2

Witness A.

Researchers in 1989 predicted that mock jurors would rate a witness to be more deceptive if the witness testified truthfully before lying than when the witness was caught lying first before telling the truth. If the availability heuristic played a role in this, lying second would remain in jurors' minds (since it was more recent) and they would most likely remember the witness lying over the truthfulness. To test the hypothesis, 312 university students played the roles of mock jurors and watched a videotape of a witness presenting testimony during a trial. Results confirmed the hypothesis, as mock jurors were most influenced by the most recent act.


Answer to Exercise 3

Being a logger.

Based on the occupational fatality rate, logging is the most dangerous job in the country and about 38 times more dangerous than the typical job.


While high-profile police shootings might lead to you think that cops have the most dangerous job, statistics actually show that loggers are more likely to die on the job than cops.


Answer to Exercise 4

Scenario (a)

In an experiment, most people estimated scenario (b) to be more likely due to an earthquake in California being a readily imaginable event. However, a flood with unspecified causes in a relatively unspecified location is necessarily more likely than one with a more specific cause and location.


Answer to Exercise 5

It may surprise you to learn that, according to the Journal of the American Medical Association, the causes of death were listed in the right order, with tobacco consumption causing the most deaths and illicit drug use causing the fewest.

Vivid deaths caused by cars, guns, and drugs tend to get a lot of press coverage. The availability of vivid stories in the media biases our perception of the frequency of events toward the last three causes over the first two. As a result, we may underestimate the likelihood of death due to tobacco and poor diet, while overestimating the hazards of cars, guns, and drugs


Answer to Exercise 6

Extraordinary work for the past 3 months.

Managers give more weight to performance during the three months prior to an evaluation than to the previous nine months of an evaluation period because it is more available in memory.


Answer to Exercise 7

Group A

Consistent with the predictions of the availability heuristic, those who were asked to generate more examples actually wound up seeing themselves as less assertive, despite the fact that they actually listed more instances of their own assertiveness. Because it was more difficult for them to come up with examples demonstrating their assertiveness, they inferred that they must not be particularly assertive.


Answer to Exercise 8

Research shows that people are more likely to purchase insurance to protect themselves from a natural disaster after experiencing one. The experience has made the natural disaster more “vivid” and readily “available” in their memory. 


Answer to Exercise 9

Showcasing the winners.

Let’s say you watch a documentary series, or see a plethora of advertisements, about the luxurious lives of those who won the lottery. After watching, you mistakenly figure that your chances of winning are higher than they actually are. Why did this happen? The documentary showcased the winner’s luxury house and brand new sports car; this left a strong impression in your mind, which will ultimately help with ease of recall. Later that day, you were feeling lucky, so you bought a Lotto 6/49 ticket with a $40 million jackpot prize.

Because of the documentary, you figured you had a decent chance of winning—after all, those people won, and they were regular people like you before buying that lucky ticket. However, you forgot the homework assignment you did for your statistics class a few years earlier where you calculated the odds of winning the 6/49 lottery as 1 in 13,983,816.8 Unfortunately, your ticket did not win, which may not have surprised you if you could’ve more easily recalled the actual odds you were up against.


Bonus Story

Many life decisions are affected by the vividness of information. Although most people recognize that AIDS is a devastating disease, many individuals ignore clear data about how to avoid contracting AIDS.

In the fall of 1991, however, sexual behavior in Dallas was dramatically affected by one vivid piece of data that may or may not have been true. In a chilling interview, a Dallas woman calling herself C.J. claimed she had AIDS and was trying to spread the disease out of revenge against the man who had infected her.

After this vivid interview made the local news, attendance at Dallas AIDS seminars increased dramatically, AIDS became the main topic of Dallas talk shows, and requests for HIV tests surged citywide. Although C.J.’s possible actions were a legitimate cause for concern, it is clear that most of the health risks related to AIDS are not a result of one woman’s actions. There are many more important reasons to be concerned about AIDS. However, C.J.’s vivid report had a more substantial effect on many people’s behavior than the mountains of data available.


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