Overview and history -------------------- edit _(cropped).jpg) Kahneman's research established that common human errors can arise from heuristics and biases . In the late 1960s and early 1970s, Amos Tversky and Daniel Kahneman began work on a series of papers examining "heuristic and biases " used in judgment under uncertainty . Prior to that, the predominant view in the field of human judgment was that humans are rational actors . Kahneman and Tversky explained that judgment under uncertainty often relies on a limited number of simplifying heuristics rather than extensive algorithmic processing. Soon, this idea spread beyond academic psychology, into law, medicine, and political science. This research questioned the descriptive adequacy of idealized models of judgment, and offered insights into the cognitive processes that explained human error without invoking motivated irrationality .[\[5\]](https://en.wikipedia.org/wiki/Availability_heuristic?utm_source=chatgpt.com#cite_note-books.google.com-5) One simplifying strategy people may rely on is the tendency to make a judgment about the frequency of an event based on how many similar instances are brought to mind. In 1973, Amos Tversky and Daniel Kahneman first studied this phenomenon and labeled it the "availability heuristic". An availability heuristic is a mental shortcut that relies on immediate examples that come to a given person's mind when evaluating a specific topic, concept, method, or decision. As follows, people tend to use a readily available fact to base their beliefs on a comparably distant concept. There has been much research done with this heuristic, but studies on the issue are still questionable with regard to the underlying process. Studies illustrate that manipulations intended to increase the subjective experience of ease of recall are also likely to affect the amount of recall. Furthermore, this makes it difficult to determine whether the obtained estimates of frequency, likelihood, or typicality are based on participants' phenomenal experiences or on a biased sample of recalled information.[\[5\]](https://en.wikipedia.org/wiki/Availability_heuristic?utm_source=chatgpt.com#cite_note-books.google.com-5) However, some textbooks have chosen the latter interpretation introducing the availability heuristic as "one's judgments are always based on what comes to mind".\_[citation needed\ _\] For example, if a person is asked whether there are more words in the English language that start with a k or have k as the third letter, the person will probably be able to think of more words that begin with the letter k, concluding incorrectly that k is more frequent as the first letter than the third.[\[6\]](https://en.wikipedia.org/wiki/Availability_heuristic?utm_source=chatgpt.com#cite_note-6) In this Wikipedia article itself, for example, there are multiple instances of words such as "likely", "make", "take", "ask" and indeed "Wikipedia", but (aside from names) only a couple of initial K's: "know" and "key". Research -------- edit Chapman (1967) described a bias in the judgment of the frequency with which two events co-occur. This demonstration showed that the co-occurrence of paired stimuli resulted in participants overestimating the frequency of the pairings.[\[7\]](https://en.wikipedia.org/wiki/Availability_heuristic?utm_source=chatgpt.com#cite_note-7) To test this idea, participants were given information about several hypothetical mental patients. The data for each patient consisted of a clinical diagnosis and a drawing made by the patient. Later, participants estimated the frequency with which each diagnosis had been accompanied by various features of the drawing. The subjects vastly overestimated the frequency of this co-occurrence (such as suspiciousness and peculiar eyes). This effect was labeled the illusory correlation . Tversky and Kahneman suggested that availability provides a natural account for the illusory-correlation effect. The strength of the association between two events could provide the basis for the judgment of how frequently the two events co-occur. When the association is strong, it becomes more likely to conclude that the events have been paired frequently. Strong associations will be thought of as having occurred together frequently.[\[8\]](https://en.wikipedia.org/wiki/Availability_heuristic?utm_source=chatgpt.com#cite_note-tversky-8) In Tversky & Kahneman's first examination of availability heuristics, subjects were asked, "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?" They argue that English-speaking people would immediately think of many words that begin with the letter "K" (kangaroo, kitchen, kale), but that it would take a more concentrated effort to think of any words in which "K" is the third letter (acknowledge, ask). Results indicated that participants overestimated the number of words that began with the letter "K" and underestimated the number of words that had "K" as the third letter. Tversky and Kahneman concluded that people answer questions like these by comparing the availability of the two categories and assessing how easily they can recall these instances. In other words, 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.[\[8\]](https://en.wikipedia.org/wiki/Availability_heuristic?utm_source=chatgpt.com#cite_note-tversky-8)