The term “availability heuristic” refers to a judgmental rule of thumb for estimating frequencies and probabilities. It states that individuals determine frequencies and probabilities “by the ease with which relevant instances come to mind” (Tversky & Kahneman 1973, 207). The logic underlying the availability heuristic holds that frequent and probable events are well represented in memory and are therefore easy to retrieve. Reversing this link, the experienced ease associated with retrieving specific events from memory can be used as an indicator for the frequency and probability of events. For example, when asked how many different game shows are currently aired on TV, one may determine how easy or difficult pertaining instances can be recalled and base the judgment on the experienced ease or difficulty associated with this recall (“If it so easy to recall examples of different game shows, then there must be many”).
The availability heuristic generally yields accurate results since frequent events are better represented in memory than infrequent ones. However, when experiences of ease or difficulty are influenced by factors other than frequency of prior exposure, the availability heuristic may be misleading. In particular, events are also more easily recalled the more recently the event occurred or was otherwise activated (recency effect), the more attention they received during encoding (salience effect), or the more the situational context of the retrieval matches the initial encoding context (congruency effect). Consequently, despite being generally accurate, the availability heuristic may produce misleading results too. As a prominent example, it has been demonstrated that individuals overestimate the prevalence of extreme causes of death, e.g., flood, homicide, tornado (Combs & Slovic 1979). The striking bias was, obviously, not a result of “reality,” but was rather a consequence of media coverage, which, it has been suggested, tends to over-report sensational events. Overreporting is likely to render extreme events very accessible, thus increasing the ease with which related pieces of information can be brought to mind. Therefore, whenever media coverage does not reflect true variation in the environment (e.g., because of overreporting of extreme events), frequency judgments are likely to be biased due to the judgmental implications of the availability heuristic.
The above examples suggest that individuals may rely on the ease or difficulty associated with retrieving information from memory when forming frequency and probability judgments. In a classic study, Tversky and Kahneman (1973) demonstrated this by asking participants whether there are more English words that begin with the letter r than those that have the letter r in the third position. Usually, individuals judge words that begin with the letter r to be more frequent those with r in the third position, despite the reverse being true. Presumably, this is because it is easier to recall words that begin with a particular letter than those in with the letter in a particular position, and the experienced ease of retrieval signals that there are many words of this kind. Although numerous studies employing different tasks and settings have supported these results, a closer look at the supporting evidence raises the questions of whether the effects of the availability heuristic are indeed mediated by experiences of ease or difficulty. On the one hand, words that begin with r are easier to recall; on the other hand, however, individuals are also likely to recall more words of this category. While the first explanation rests on the experienced ease as initially hypothesized by Tversky and Kahneman, the second explanation rests on the content information that is recalled. Addressing this confusion, Schwarz et al. (1991) developed a paradigm that allows for disentangling the competing explanations of ease versus content. Participants recalled either six or 12 instances of prior self-assertive behavior and subsequently judged their own self-assertiveness. As recalling six instances is easy, while recalling 12 is difficult, the implications of experienced ease versus recalled content information were diametrically opposed. In particular, if participants relied on their experiences of retrieval ease, they would judge their own self-assertiveness more positively after recalling six (easy) rather than 12 (difficult) instances – after all, if it is easy to come up with instances, one has to be self-assertive (and vice versa for experiences of difficulty). Contrarily, if participants relied on the content information, they would judge their own self-assertiveness more positively after recalling many rather than few instances, because more material was retrieved from memory. Judgmental results were in accordance with the easebut not the content-explanation, thus underscoring that the effects of the availability heuristic are indeed mediated by experiences of ease or difficulty.
Three recent developments deserve particular mention. For one, it has been demonstrated that not only judgments of frequency and probability, but also evaluative judgments of many kinds may be affected by experiences of ease or difficulty. For instance, judgments about consumer products, about health-related issues, or about other individuals may be informed by the ease with which relevant pieces of information come to mind.
In a more loose relation to the original idea that ease of retrieval influences judgments of frequency and probability, one could speculate that individuals may draw inferences about the importance or adequacy of a given topic for the present situation. If this were the case, issues that are strongly covered in the media – and are thus easily accessible – would be considered important because they come to mind so easily. Such a mechanism could account for the agenda-setting function of the media, besides a more traditional mere priming approach.
Moreover, one may ask how often or when individuals rely on the experienced ease as opposed to the recalled content? First, experiences of retrieval ease are likely to be relied on in conditions of low processing motivation/capacity, that is, when individuals either do not want to or cannot invest much cognitive resources in the formation of judgments and decisions. Second, experiences of retrieval ease are likely to be relied on if individuals are in a positive (rather than negative) mood state, or if individuals are low (rather than high) in depressive symptomatology. Third, experiences of retrieval ease are likely to be relied on if individuals currently or dispositionally experience uncertainty. Finally, experiences of retrieval ease are likely to be relied on only if they are perceived to be diagnostic for the judgment in question.
- Combs, B., & Slovic, P. (1979). Newpaper coverage of causes of death. Journalism Quarterly, 56(4), 837– 843.
- Schwarz, N. (2004). Metacognitive experiences in consumer judgment and decision making. Journal of Consumer Psychology, 14, 332 –348.
- Schwarz, N., Bless, H., Strack, F., Klumpp, G., Rittenauer-Schatka, H., & Simons, A. (1991). Ease of retrieval as information: Another look at the availability heuristic. Journal of Personality and Social Psychology, 61, 195 –202.
- Tversky, A., & Kahneman, D. (1973). Availability: A heuristic for judging frequency and probability. Cognitive Psychology, 5, 207–232.