Omission Bias

What is omission bias?

Omission bias is a tendency to judge harm caused by an action more harshly than comparable harm caused by inaction, even when relevant consequences and intentions are held constant.

Spranca, Minsk and Baron (1991) studied moral judgments about matched omissions and commissions. Their findings support a distinction in how people assess the actor's involvement, not a general rule that inaction is safer.

An example of omission bias

In a fictional tennis scenario used by Spranca and colleagues, John knows that his opponent is allergic to an ingredient in the restaurant’s house dressing. He wants the opponent to become ill so he can win their match. In one ending, John recommends that dressing. In another, the opponent orders it independently and John deliberately fails to warn him.

In both endings, the opponent gets the same stomachache and John wins the match. John knows about the allergy and seeks the same advantage in both. Many participants nevertheless judged the deliberate silence less harshly than the recommendation. Participants judged a written scenario; no actual poisoning took place.

Action and inaction can differ in duties, consent, uncertainty and consequences. Such differences must be checked before a preference for inaction is called a bias. Comparing both options explicitly is a useful decision check. A preference for doing nothing is a starting point for a question, not proof that the person has made an error.