Where it is used

Design, policy and daily life.

Applied

Public health messaging, energy use campaigns, tax compliance letters and organ donation defaults all draw on social norms and defaults, with measurable and usually modest effects.

Telling people what most others do changes behaviour, in both directions.
Effects are often small; scale is what makes them worth doing.

For yourself

Choose environments deliberately, since they shape behaviour more than resolve does. That single application is worth more than the whole catalogue of effects.