When we use the availability heuristic, we place particular weight on examples of things that come to mind easily, perhaps because they are easily remembered or recently encountered. In general, this guides us in the right direction, as things that come to mind easily are likely to be common, but it may also mislead. The availability heuristic is apparent after a major train crash, when some people choose to travel by car instead of by rail, in the incorrect belief that it is safer.w7
In the medical setting, one study asked doctors to judge the probability that medical inpatients had bacteraemia. The probability was judged to be significantly higher when doctors had recent experience of caring for patients with bacteraemia.10
Another example is the documented tendency of doctors to overestimate the risk of addiction when prescribing opioid analgesics for pain relief and to undertreat severe pain as a result.11-13
Risk of addiction is actually low when patients receive opioids (particularly controlled release formulations) for pain,14,15
but opiate addiction tends to receive high publicity and so—through the availability heuristic—its likelihood may be overestimated.
To avoid falling prey to the availability heuristic, doctors should try to be aware of all the diverse factors that influence a decision or diagnosis. They should ask if their decision is influenced by any salient pieces of information and, if so, whether these pieces of information are truly representative or simply reflect recent or otherwise particularly memorable experiences. Knowing whether information is truly relevant, rather than simply easily available, is the key.
Rules for good decision making
- Be aware of base rates
- Consider whether data are truly relevant, rather than just salient
- Seek reasons why your decisions may be wrong and entertain alternative hypotheses
- Ask questions that would disprove, rather than confirm, your current hypothesis
- Remember that you are wrong more often than you think