Availability Heuristic

There seemed no way to make up
Because it seemed your mind was set
And the way you looked and told me
That's a look I know I'll never forget
--Phil Collins

The availability heuristic (Tversky & Kahneman, 1973) is a rule of thumb that people use to judge the frequency and probability of events based on the ease with which examples come to mind. Memories that are, for example, vivid, full of emotion, and/or recent are likely to be favored when estimating frequency or likelihood of occurrence.

This can lead to systemic bias and error in judgment. The classic example is the event of a catastrophe. Catastrophes, by definition, are rare events with extremely negative consequences. Natural disasters, stock market crashes, and unexpected death of loved ones exemplify catastrophe.

Following catastrophes, people are likely to overestimate how often similar events have happened in the past; people are also apt to overweight the likelihood of the recurrence of similar catastrophes in the future.

This is consummate System 1 activity.

In his book, Kahneman recounts a particular time when he was living in Israel. A string of terrorist bombings had occurred--many of them taking place on buses. Kahneman recalls feeling anxious every time his car pulled alongside a bus at traffic intersections--to the point where he was tempted to run red lights to avoid perceived danger. In reality, the actual probability of his being near a potential terrorist event was tiny.

Fear of catastrophic events drive many people to purchase insurance--often after such rare events have already occurred and when insurance premiums are steep.

In the public sphere, politicians understand the availability heuristic well. They know that people are willing to surrender much freedom in exchange for protection against the recurrence of recent tragic loss.

Because those looking to assimilate power relish crises as opportunities, people would be wise to examine their thought processes during difficult times for evidence that the availability heuristic may be selling them short.

Reference

Tversky, A. & Kahneman, D. 1973. Availability: A heuristic for judging frequency and probability. Cognitive Psychology, 5(2): 207-232.