Confirmation Bias

“Confirmation bias, also called myside bias, is the tendency to search for, interpret, or recall information in a way that confirms one’s beliefs or hypotheses.”[1]

An example of this is the casual prescribing of an intervention for an unconfirmed diagnosis or for the right diagnosis but for an ineffective therapy, especially for a self-limiting disease.

On follow-up, the patient is noted to be improved or the clinical signs resolved. For an incorrect diagnosis, this may lead to the false presumption that the diagnosis was correct and the treatment effective. For a correctly identified condition (e.g. a self-limiting mild viral upper respiratory infection), the prescribing of antibiotics may also lead to the incorrect conclusion that the treatment was also effective.

If antibiotics are given to assuage client concerns, even though it’s known of their lack of effiacy, this would be commission bias.

In veterinary medicine, confirmation bias is exhibited by clinicians as well as clients.

See “Why We’re Often Wrong: Can We Trust Clinical Experience” on the SkeptVet blog.

Read more in-depth essays at Science Daily,, Skeptic’s Dictionary or from SkepticalMedicine.

Also see Identifying and Avoiding Bias in Research by Pannucci and Wilkins, or A clinician-educator’s roadmap to choosing and interpreting statistical tests by Windish and Diener-West.

[1] Confirmation Bias @ Wikipedia


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