Omission Bias

We judge harmful actions as morally worse than equally harmful inactions — even when the outcomes are identical. We are more disturbed by active harm than passive harm.

• Vaccine hesitancy: parents fear the rare side effect of vaccination (an action) far more than the disease risk of not vaccinating (an inaction) — even when the math clearly favors vaccination.
• A train conductor who actively switches tracks and kills one person seems worse to us than one who passively does nothing and kills five.
• Investors hold onto losing stocks (inaction) rather than sell at a loss (action) — even though both result in equivalent financial damage.