The Availability Heuristic is a judgment shortcut by which individuals estimate the likelihood or frequency of an event based on how easily examples or instances come to mind. In essence, the more accessible or readily available an option is, the more likely people tend to judge that outcome to be.
This heuristic was named and first described by the psychologists Amos Tversky and Daniel KahnemanDaniel Kahneman and Amos Tversky are pioneering Israeli psychologists whose collaboration profoundly impacted the the science of judgment and decision making and behavioral economics. Their... in the 1970s, forming a cornerstone of their groundbreaking work in behavioral decision theory. Along with the Representativeness HeuristicLink to Wikipedia entry The representativeness heuristic is one of the most widely researched and demonstrated cognitive heuristics (short cuts or rules of thumb putatively... More and, in a modified form, Anchoring, it is one of the “big three” heuristics in the Heuristics and Biases tradition that they pioneered. From their perspective, heuristics operates automatically and unconsciously, a part of what Kahneman has associated with System 1 as opposed to System 2 (conscious, deliberative reasoning); they are part of human cognitive architecture and thus shared across the human species, built in, and resistant to training or other attempts to diminish their impact on judgment.
Tversky and Kahneman recognize that the availability heuristic—like their other proposed heuristics—is usually adaptive. On average, availability is a strong indicator of likelihood and it helps people make quick judgments, often in cases when more reliable cues are unavailable (pun intended). That said, it leads to systematic errors or misjudgments (biases) when the most memorable events are not the most representative or frequent, as is often the case for the most sensational events (since their rarity or unusualness is often part of what makes them particularly newsworthy) such as plane crashes or terrorist, bear, or shark attacks. In these cases, the heuristic may prevail even in cases where people have access to more reliable cues that contradict the availability heuristic.
See the Wikipedia entry for a more complete discussion.
In the context of gambling, availability has been used in part to explain why gambler’s overweight more recent events in strategies that seem to rely on the gambler’s fallacyIn decision science, bias refers to systematic and predictable deviations from accepted models of rationality. In scientific language, "systematic" and "predictable" are not meant to... or belief in the hot hand.