Table 1.

Summary description of heuristics and biases

Heuristic	Definition	Unit of analysis	Heuristic and/or bias	Detection algorithm
Anchoring	Locking on to salient evidence early in the diagnostic process leading to an initial diagnosis	Single case	Heuristic	Participant adds a hypothesis, then adds findings, and then adds a diagnosis supported by the new findings. The diagnosis may be (1) the same as the hypothesis (sufficient nonadjustment) or (2) different than the hypothesis (sufficient adjustment) as long as the findings support the subsequent diagnosis
			Bias	Participant adds a hypothesis, then adds findings, and then adds a diagnosis that is not supported by the new findings. Participant does not subsequently add hypothesis or diagnosis consistent with all new findings (insufficient adjustment)
Availability	The disposition to judge things as either more likely or as frequently occurring if they come to mind readily	Case sequence	Bias	In a sequence of three cases where the third case has a different diagnosis than the first two cases, the participant makes an incorrect diagnosis in the third case. The incorrect diagnosis is identical to the correct diagnosis in the two immediately preceding cases
Confirmation bias	The tendency to look for confirming evidence to support a diagnosis rather than looking for disconfirming evidence to refute it	Single case	Bias	Participants adds an incorrect diagnosis, and then adds findings that support this incorrect diagnosis
Gambler’s Fallacy	The belief that when deviations from expected results occur in repeated independent events, it increases the likelihood of deviations in the opposing direction, leading the clinician to reject a diagnosis because the entity has been observed more frequently than expected in recent cases	Case sequence	Bias	In a sequence of three cases where all three cases have the same diagnosis, the participant makes a diagnosis in the first case, the same diagnosis in the second case, but a different and incorrect diagnosis in the third case. In the first two cases, the participant’s diagnosis may be either correct or incorrect
Representativeness (Type 2)	The tendency to judge an entity against a mental model based on similarity to a prototype, leading the clinican to rigidly associate a feature with a single disease, based on a learned model	Case sequence	Heuristic	Participant adds a finding and then immediately (in the next action) adds a correct diagnosis. This sequence of actions must have been observed more than once during the session. The relationship between the finding and the diagnosis must have been included in the study period
			Bias	Participant adds a finding and then immediately (in the next action) adds an incorrect diagnosis. This sequence of actions must have been observed more than once during the session. The relationship between the finding and the diagnosis must have been included in the study period
Search Satisficing	The tendency to call off a search once something has been found, leading to premature diagnostic closure	Case sequence	Bias	Participant adds a hypothesis and then adds a diagnosis without intervening findings. The diagnosis must be incorrect or the differential diagnosis must be incomplete. The case must be immediately closed. If any findings are added during the case, they must precede the addition of the hypotheses
Overconfidence and underconfidence	The belief in one’s own performance, with extremes representing opposite ends of a spectrum of feeling-of-knowing	Case sequence	Bias	Based on the comparison of participant self assessment to performance for all items. Bias is computed as result of the subtraction of total correct from total sure, divided by total items, and range from +1 (completely overconfident) to −1 (completely underconfident), with an optimum value of zero indicating perfect matching between their confidence and performance