Politicians and police are actively encouraging us to intervene if we witness violence on the street.
But why do some of us become natural 'have a go heroes' in these situations, while others chose to 'walk on by'?
In an attempt to find out, Nick Ross meets the people studying the psychology of how we respond when we witness violent behaviour.
His investigation uncovers surprising CCTV evidence that people are actually much more likely to intervene than previously suspected.
And he takes part in virtual reality experiments in which people's responses to emerging violence are tested using life-size and frighteningly realistic avatars.
The 'bystander effect', he learns, suggests that the more people who witness a violent event, the less likely it is that any individual will intervene.
And this phenomenon turns out to be equally true in cyberspace.
Producer: Brian King
An Above The Title production for BBC Radio 4.
The new Home Secretary, Theresa May has called on the public to 'have a go' if they witness violence on the street, promising legislation to protect 'good Samaritans' from falling foul of the law themselves.
Nick Ross explores the psychology of why some people intervene and others don't.
To the alarm of his family, Nick doesn't walk on by.
He tends to get stuck in; once actually making a citizen's arrest.
But studies have shown that the British public in general are the least likely in Europe to intervene if they witness crime or anti-social behaviour.
The so-called 'bystander effect' dictates that the larger the group of people who witness a violent attack, the less likely it is that someone will intervene.
The programme hears from psychologists who suspect that people often fail to intervene because they believe no-one else will get involved.
This assumption is fuelled by media coverage of cases in which people have been seriously injured or even killed while bystanders stand and watch.
Non-intervention becomes a self-fulfilling prophecy.
But Nick meets psychologist Mark Levine whose extensive study of CCTV footage of street violence suggests that groups do much more to try to defuse aggressive behaviour than is generally realised.
Nick steps into a virtual reality cave to see how people's reaction to violence is being tested in frighteningly realistic scenarios using avatars and meets the psychologist who is studying a 'walk on by' syndrome on the internet.
Evolutionary biology suggests that our natural, genetic instinct is to behave in an altruistic and supportive way if we witness someone being attacked.
So if, in modern society, we fail to do so, something would appear to have gone badly wrong.
Producer: Brian King
An Above The Title production for BBC Radio 4