Thinking, Fast and Slow: Part 2, Chapter 12 Summary & Analysis

Kahneman and Tversky spent 1971-72 at the Oregon Research Institute, studying what they called the “availability heuristic.” This heuristic describes the thought process that people use when they estimate the frequency of a category, like “people who divorce over the age of 60.” They often judge frequency by the ease with which instances of that category come to mind.

Kahneman and Tversky considered how many instances must be retrieved to get an impression of ease. The answer is none. If presented with the strings of letters “XUZONLCJM” and “TAPCERHOB” we immediately know, without generating any instances, that far more words can be constructed with the second string of letters.

The availability heuristic substitutes the question “how frequent or how sizeable is this category?” with “how easily can I think of examples of this category?” Events that attract attention (like celebrity divorces), dramatic events in the news (like plane crashes), and personal experiences, pictures, and vivid examples will all alter our sense of how frequent they are.

The availability heuristic explains why we overestimate our own contributions to group activities. When spouses are asked to estimate the percentage of the housework that they do, their responses usually add up to more than 100%.

In the early 1990s, German psychologists led by Norbert Schwarz studied how people’s impressions of frequency are affected by requirements to come up with specific examples of that category. They asked people to list six (or, in another group, twelve) instances in which they behaved assertively, and then to evaluate how assertive they are. They wanted to see whether people would base their evaluation on the number of examples they could come up with, or the ease with which they could come up with them. The results yielded a clear-cut winner: people who had listed twelve instances rated themselves as less assertive than people who listed six.

This result is paradoxical, and it is due to the strain of coming up with more examples. When Schwarz provided an explanation for the difficulty (i.e., by telling participants that the background music would affect performance in the memory task), they rated themselves equally assertive when coming up with six or twelve examples.

Schwarz and his colleagues discovered that people who are personally involved in the judgment are more likely to consider the number of instances they retrieve and less likely to go by fluency. Students with no family history of heart disease were asked to recall three or eight behaviors that could affect their health. They felt safer if asked to retrieve many risky behaviors (which they found hard to do). Students with a family history of heart disease felt greater danger when they retrieved many instances of risky behavior.

People are more affected by ease of retrieval than by content if they meet certain conditions, including the following: if they are engaged in another effortful task at the same time, if they are in a good mood, if they have a large amount of faith in intuition, or if they are made to feel powerful.