BUT SURELY IT'S A COINCIDENCE...:

Life is rife with coordination problems. Consider passing someone on the street going the other way. You both have a shared incentive to coordinate about which side of the sidewalk to walk on, so that you don't bump into each other. Even though the other person is a complete stranger, there is no particular reason she would try to deceive you. In such circumstances, people will send signals (eg, stop before making a sudden exaggerated movement toward one side) to successfully coordinate. Mathematical models show that these costless signals can be crucial in helping people solve otherwise thorny coordination problems.

Coordination is crucial in the moral domain too. Imagine you live in a society that practises slavery, and you think you are the only one morally revulsed by it. Should you speak out about your concerns? If you think that everyone else is indifferent, you might be afraid that others will think you are weird, that the people benefiting from the system will punish you, and that you stand no chance to make a difference anyway.

The paradox is that, even if many people are in this situation - everyone is concerned but convinced that no one else is - they might fail to act, despite having the majority opinion. But speaking up can start a chain reaction. The more individuals raise their voice to denounce what they see as a moral problem, the more the initially silent people realise they are not alone and speak up in turn.

When everyone can expect everyone to know, it is harder for you to claim ignorance as a defence

Loud and public signals are especially effective as establishing common knowledge of a moral norm ­making sure that everyone knows about the moral norm, that everyone else knows that everyone knows about the moral norm, that everyone knows that everyone knows that everyone knows (and so on). Psychology experiments have demonstrated that common knowledge is a powerful determinant of social behaviour: people are much more likely to coordinate on a joint action when everyone knows that everyone knows that working together will generate good outcomes.

In addition to fostering coordination, common knowledge prevents people from hiding behind the veil of plausible deniability. To get away with selfish behaviour, we often pretend to ignore its consequences. If you can plausibly say that you didn't know about the poor working conditions of people in sweatshops, people will judge you less harshly for buying cheap clothes. But if many people virtue signal by campaigning for better workers' rights, the issue rises to common awareness - and, when everyone can expect everyone to know, it is harder for you to claim ignorance as a defence.

Viewing morality as a coordination game suggests that public opinion can undergo rapid shifts, as society coordinates on new moral norms. And this is indeed what we observe: public opinion on a variety of subjects - such as racism and gay rights - has shifted dramatically in a progressive direction over the past few decades (sometimes within a few weeks).

In sum, virtue signalling can be a powerful force for social change, by creating common knowledge around a moral issue that people would otherwise ignore (out of complacency or selfishness). Importantly, this works even when there is no guarantee the people who are sending the signals are particularly virtuous or committed to the cause.

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