When norm change hurts.

Applied cultural evolution includes any effort to mobilize social learning and cultural evolution to promote behaviour change. Social tipping is one version of this idea based on conformity and coordination. Conformity and coordination can reinforce a harmful social norm, but they can also accelerate change from a harmful norm to a beneficial alternative. Perhaps unfortunately, the link between the size of an intervention and social tipping is complex in heterogeneous populations. A small intervention targeted at one segment of society can induce tipping better than a large intervention targeted at a different segment. We develop and examine two models showing that the link between social tipping and social welfare is also complex in heterogeneous populations. An intervention strategy that creates persistent miscoordination, exactly the opposite of tipping, can lead to higher social welfare than another strategy that leads to tipping. We show that the potential benefits of miscoordination often hinge specifically on the preferences of people most resistant to behaviour change. Altogether, ordinary forms of heterogeneity complicate applied cultural evolution considerably. Heterogeneity weakens both the link between the size of a social planner's intervention and behaviour change and the link between behaviour change and the well-being of society. This article is part of the theme issue 'Social norm change: drivers and consequences'.