A few years ago, Facebook managers noticed a rush of complaints from users about friends posting photographs of them that they didn’t like. The pictures weren’t explicit; they just reminded users of something they would rather forget, or made them look stupid. These complaints were invariably rejected because no rules had been broken, yet friendships were being strained as a result. “We tried saying, ‘Why don’t you just message the person?’, but people didn’t quite know what to say,” says Milner, adding tactfully that not everybody “has the social skills” to resolve such petty squabbles. So, Facebook introduced social reporting, which works like a teacher gently helping kids in a playground dispute to resolve things between themselves. Complainants get a template message to send to their friend, explaining how the picture makes them feel and asking politely for its removal. Usually, that’s all it takes – it is, says Milner, “helping you have an empathetic response” that leaves everyone feeling good. “We set up our systems to encourage people to be nice – to think about things before you post.” It’s a classic example of what BJ Fogg, a Stanford-based behavioural scientist who specialises in the psychology of Facebook, calls persuasive design: if you want people to do something, don’t explain why, just show them how. Humans learn by imitation, which means modelling nice behaviour beats lecturing people to be nice.