How much empathy do you feel towards other people? If you saw someone fall off their bike in traffic, would you sTOP and help - or just walk away? Many people would give in to apathy1, go about their business and just do nothing. So it was a big surprise when about 100 bystanders got together recently to move a bus in east London to help a cyclist trapped under it. A video of the incident went viral on social media.

According to Zoheb, a driver who sTOPped his car to take part in the rescue, about five people gathered to move the bus. He says: There was no chance we could do it, it was more an invitation for other people to help, really.

The initiative paid off. Diners from nearby restaurants joined in. There wasnt much coordination2 but it didnt take long to develop a collective understanding of what the objective was.

Spontaneous collaboration3 among strangers doesnt happen often. People in a crowd are not sure what to do - they dont have a plan. Its one of the reasons bystanders often do nothing, according to Dr Mark Levine, professor of social psychology4 at Exeter University in Britain. The presence of others can inhibit5 you from helping6, he says.

The key to positive group behaviour and intervention7, Levine explains, is building a sense of shared identity. Action has to be decided8 quickly, Levine says. The longer you leave it, the harder it is to make a decision. If you dont immediately act then you kind of think Well, actually I probably couldnt have done anything anyway.

But the people who took the initiative like Zoheb might make a difference. The cyclist ended up in hospital and the images of the collective effort might inspire others to more acts of solidarity9.