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TABLE 1

Definitions of Common Cognitive Biases

Cognitive BiasDefinition
Anchoring bias or diagnostic momentum Too much wt is assigned to the earliest or most salient features of a patient’s history or test results, and other evidence to the contrary is ignored. Diagnosis momentum: once diagnostic labels are attached to patients they tend to become stickier and stickier. Through intermediaries, (patients, paramedics, nurses, physicians) what might have started as a possibility gathers increasing momentum until it becomes definite and all other possibilities are excluded. An example of diagnostic momentum is: triage cueing: when diagnostic decisions are influenced by the original triage category a patient is placed in, such as when the triage nurse diagnosed the patient as “not sick,” therefore the patient must not be sick. There are many forms of triage, from patients self-triaging to different levels of care, to the referrals you make out of the ED that cue your consultants based on your assessment. 
Premature closure or satisfaction Once a clinician arrives at a plausible diagnosis, the clinician accepts it as the best diagnosis and stops asking questions to seek an alternative diagnosis, even if a comprehensive history or workup is not yet complete. Satisfaction: the tendency to stop searching once you have found something (this is the reason we miss the second fracture on x-ray once we identify the first, or identifying a coingestion once we have identified the first) 
Confirmation bias Once a clinician arrives at a diagnosis, all future evidence aligning with that diagnosis is considered confirmation of its accuracy, whereas any contrary evidence is subconsciously ignored. 
Overconfidence Clinicians’ confidence in their diagnosis remains constant regardless of their accuracy. 
Halo effect It is the tendency for an initial impression of a person to influence what we think of them overall. 
Availability bias The disposition to judge things as being more likely, or frequently occurring, if they readily come to mind. Thus, recent experience with a disease might inflate the likelihood of its being diagnosed. Conversely, if a disease has not been seen for a long time (is less available), it might be underdiagnosed. 
Hindsight bias Knowing the outcome might profoundly influence perception of past events and prevent a realistic appraisal of what actually occurred. In the context of diagnostic error, it may compromise learning through either an underestimation (illusion of failure) or overestimation (illusion of control) of the decision maker’s abilities. 
Perception bias The tendency to believe one thing about a group of people based on stereotype and assumptions, making it impossible to be objective about individuals. 
Ascertainment bias This is a term used in research or Evidence Based Medicine, but here it means the following: When your thinking is shaped by prior expectations. In other words, you see what you expect to see. This is the umbrella category that contains stereotyping and gender bias. For example, a teenage patient with past drug use is found unconscious and it is assumed that they have overdosed, when in fact they have severe hypoglycemia. 
Cognitive BiasDefinition
Anchoring bias or diagnostic momentum Too much wt is assigned to the earliest or most salient features of a patient’s history or test results, and other evidence to the contrary is ignored. Diagnosis momentum: once diagnostic labels are attached to patients they tend to become stickier and stickier. Through intermediaries, (patients, paramedics, nurses, physicians) what might have started as a possibility gathers increasing momentum until it becomes definite and all other possibilities are excluded. An example of diagnostic momentum is: triage cueing: when diagnostic decisions are influenced by the original triage category a patient is placed in, such as when the triage nurse diagnosed the patient as “not sick,” therefore the patient must not be sick. There are many forms of triage, from patients self-triaging to different levels of care, to the referrals you make out of the ED that cue your consultants based on your assessment. 
Premature closure or satisfaction Once a clinician arrives at a plausible diagnosis, the clinician accepts it as the best diagnosis and stops asking questions to seek an alternative diagnosis, even if a comprehensive history or workup is not yet complete. Satisfaction: the tendency to stop searching once you have found something (this is the reason we miss the second fracture on x-ray once we identify the first, or identifying a coingestion once we have identified the first) 
Confirmation bias Once a clinician arrives at a diagnosis, all future evidence aligning with that diagnosis is considered confirmation of its accuracy, whereas any contrary evidence is subconsciously ignored. 
Overconfidence Clinicians’ confidence in their diagnosis remains constant regardless of their accuracy. 
Halo effect It is the tendency for an initial impression of a person to influence what we think of them overall. 
Availability bias The disposition to judge things as being more likely, or frequently occurring, if they readily come to mind. Thus, recent experience with a disease might inflate the likelihood of its being diagnosed. Conversely, if a disease has not been seen for a long time (is less available), it might be underdiagnosed. 
Hindsight bias Knowing the outcome might profoundly influence perception of past events and prevent a realistic appraisal of what actually occurred. In the context of diagnostic error, it may compromise learning through either an underestimation (illusion of failure) or overestimation (illusion of control) of the decision maker’s abilities. 
Perception bias The tendency to believe one thing about a group of people based on stereotype and assumptions, making it impossible to be objective about individuals. 
Ascertainment bias This is a term used in research or Evidence Based Medicine, but here it means the following: When your thinking is shaped by prior expectations. In other words, you see what you expect to see. This is the umbrella category that contains stereotyping and gender bias. For example, a teenage patient with past drug use is found unconscious and it is assumed that they have overdosed, when in fact they have severe hypoglycemia. 
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