The availability heuristic is a mental shortcut that relies on immediate examples that come to mind. The availability heuristic operates on the notion that if something can be recalled, it must be important (“if you can think of it, it must be important.”). Subsequently, people tend to heavily weigh their judgments toward more recent information, making new opinion biased toward that latest news.  Further, the availability of consequences associated with an action is positively related to perceptions of the magnitude of the consequences of that action. In other words, the easier it is to recall the consequences of something, the greater we perceive these consequences to be. Finally, people not only consider what they recall in making a judgment but also use the ease or difficulty with which that content comes to mind as an additional source of information. Most notably, they only rely on the content of their recall if its implications are not called into question by the difficulty that they experience in bringing the relevant material to mind.

The following are three heuristic principles that people rely on in situations of uncertainty. These principles reduce the complex task of assessing probabilities and predicting values to simpler judgmental operations.

  1. Representativeness, which is usually employed when people are asked to judge the probability that an object or event A belongs to class or process B.
  2. Availability of instances or scenarios, which is often employed when people are asked to assess the frequency of a class or the plausibility of a particular development.
  3. Adjustment from an anchor, which is usually employed in numerical prediction when a relevant value is available.

Sometimes the heuristic is beneficial, but the frequencies that events come to mind are usually not accurate reflections of their actual probability in real life. For example, if a student is asked whether her college had more students from Colorado or more from California, her answer would probably be based on the personal examples she is able to recall.

When faced with the difficult task of judging probability or frequency, people use a limited number of strategies, called heuristics, to simplify these judgements. One of these strategies, the availability heuristic, is the tendency to make a judgement about the frequency of an event based on how easy it is to recall similar instances.

The familiarity heuristic stems from the availability heuristic which was studied by Tversky andKahneman. The availability heuristic suggests that the likelihood of events is estimated based on how many examples of such events come to mind. Thus the familiarity heuristic shows how “bias of availability is related to the ease of recall.”

Tversky and Kahneman created an experiment in order to test this heuristic. They devised four lists of 39 names. Each list contained 19 female names and 20 male names. Half of the lists had famous female names, and the other half had famous male names. They showed the lists to two test groups. The first group was shown a list and asked to recall as many names as possible. The second group was shown a list and asked to determine if there were more female or more male names. The subjects who heard the list with famous female names said there were more female names than there were male names. Similarly, the subjects who heard the list with famous male names recalled more male names than female names. Thus the familiarity heuristic is defined as “judging events as more frequent or important because they are more familiar in memory.”

The familiarity heuristic is based on using schemas or past actions as a scaffold for behavior in a new (yet familiar) situation. This is useful because it saves time for the subject who is trying to figure out the appropriate behavior for a situation they have experienced before. Individuals automatically assume that their previous behavior will yield the same results when a similar situation arises. This technique is typically useful. However, certain behaviors can be inappropriate when the situation is different from the time before.

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