Dissent plays a vital role in driving social change, but can be limited when individuals fear social sanction for expressing opinions about controversial issues.

This column explores the function of rationales in facilitating dissent on both sides of the US political spectrum.

Using a simple theoretical framework, it shows that liberals are more willing to post a tweet opposing movements to defund the police – and indeed face fewer social sanctions – when their tweet implies they have read scientific evidence supporting their position.

Analogous experiments with conservatives demonstrate that the same mechanisms facilitate anti-immigrant expression.