Availability bias causes people to overestimate the likelihood of memorable events, leading to societal prejudice. People often believe rare events, such as plane crashes and child abductions, are more common than they are. Availability bias underlies many other biases and cultural effects. The concept of abandoning the base rate is related to availability bias. Psychologists Tversky and Kahneman founded the field of “heuristics and biases” and developed perspective theory to explain systematic bias in human decision making.
Availability bias is a human cognitive bias that causes people to overestimate the likelihood of events associated with memorable or vivid events. As memorable events are further magnified by media coverage, prejudice is compounded on a societal level. Two important examples would be estimates of the likelihood of plane crashes and the frequency with which children are abducted. Both events are quite rare, but the vast majority of the population believe they are more common than they are and act accordingly.
In fact, people are much more likely to die in an automobile accident than in a plane crash, and children are more likely to die in an accident than to be kidnapped. Most people think the opposite is true, however, because less probable events are more “available,” more memorable. Looking at the literature or even just daily life interactions will reveal thousands of examples of availability bias in action.
Availability bias underlies many other human biases and cultural effects. For example, medieval medicine was probably barely more effective than leaving an illness alone to heal on its own, but since the times when therapy “worked” are more readily available in the minds of many, practicing medicine was generally considered effective regardless of the fact that it really was.
The study of this bias was initiated by psychologists Amos Tversky and Daniel Kahneman, who founded the field of “heuristics and biases” and developed a model called perspective theory to explain systematic bias in human decision making. Kahneman subsequently won the Nobel Prize in Economics in 2002 for his work, despite the fact that he had never taken an economics course. Tversky, his longtime partner in heuristics and bias research, died in 1996.
A concept intimately related to the availability bias is that of abandoning the base rate. Base rate abandonment refers to integrating irrelevant information into a probability judgment, distorting it from the natural base rate. An example would be getting someone into college based on an interview alone, when empirical studies have shown that past performance and grades are the best possible indicator of future performance, and that interviews only cloud the assessment. However, because people like to “see things for themselves,” interviews are likely to continue to take place, even in the absence of any support for their effectiveness.
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