Table 1 Illustrative medical examples of selected heuristics

Availability:

Estimating the likelihood of an event (X) by the ease with which instances of X come to mind, i.e., how available they are.

Recent experiences caring for patients with bacteremia were associated with doctors' higher estimated probabilities that hospital inpatients (for whom blood cultures had been taken) had bacteremia [16].

Representativeness:

Where estimating the likelihood of an event (X) is mediated by the degree to which it represents the class to which X belongs.

Drives the diagnostician toward looking for prototypical manifestations of disease: "If it looks like a duck, walks like a duck, quacks like a duck, then it is a duck." Yet restraining decision-making along these pattern-recognition lines leads to atypical variants being missed [17]. It inappropriately ignores, for example, prior probabilities [18].

Affect:

Where an initial affective reaction biases the resultant decision.

When toxicologists were asked to assess the risk associated with a very small exposure to 30 chemical items, degree of risk was mediated by their assessment of how 'bad-good' each chemical was [19].