Glossary
Semmelweis Reflex
What is the Semmelweis reflex?
The Semmelweis reflex is an informal label for dismissing new evidence because it conflicts with an established belief.
The historical example
Ignaz Semmelweis documented a large reduction in deaths from childbed fever after introducing chlorine hand disinfection in a maternity clinic. His work faced opposition, although not every contemporary physician rejected it.
What the label means
The phrase warns against rejecting evidence without examining it. It is not a distinct, experimentally established reflex. Research by Ross, Lepper, and Hubbard examines the related problem of belief perseverance, rather than the named historical “reflex.”
An unpopular idea can be right. It can also be wrong. The evidence decides, not the opposition it attracts.