I hear that a lot about Singapore. The thing most people don't seem to realise is that in 1960 Singapore was essentially a giant slum.

All these "collective" behaviours have appeared since then helped along by government campaigns: https://remembersingapore.org/2013/01/18/singapore-campaigns...

(Note that one of those campaigns - speak Mandarin - was encouraging people to abandon their native languages and learn a completely different one. It was highly successful. I think by comparison "don't throw litter" would be extremely easy.)