Health psychology/Cognitive biases · Clinical reasoninglow yield

Omission bias

What it means

Judging harm caused by ACTING as worse than equal or greater harm caused by inaction — a bias toward doing nothing.

Worked example

Withholding a beneficial vaccine because a rare vaccine harm feels worse than the larger harm of the disease prevented.

In the exam

A parent refuses a vaccine because a rare reaction caused by giving it would feel far worse to them than the greater risk of the disease it prevents.

What settles it

Omission bias over-weights harm from ACTING versus equal harm from inaction. Sunk cost is persisting with a plan because of prior investment — here it is the action/inaction asymmetry itself.

Classically confused with

Sunk cost bias

Source: Croskerry