"You have no business in this street, you have broken the quarantine regulation", read the note posted through the window of Sarah Crossland's car.

Far from flouting the rules of lockdown, Ms Crossland had been delivering food to a vulnerable person in Morley, Leeds when the message was pushed through a crack in her car window.

Unfortunately, it's not the only example of over-zealous vigilantism that's been highlighted in recent weeks.

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Why are we policing each other?

Since the lockdown was announced on 23 March, public shaming - both online and in person - has become a regular part of life across the UK.

And while some people have been purposely breaking the rules of lockdown, many more have found themselves victim to shaming while out performing key work, exercising, or delivering essential supplies.

When directed against big businesses, public shaming has - in some cases - been effective at preventing poor behaviour towards employees.

Pub chain JD Wetherspoon, for instance, made a dramatic U-turn on their policy not to pay employees who couldn't work after an outpouring of public protest online.

But why is it that the current crisis has made so many people turn to policing individuals - even when their behaviour is in line with government guidance?

Acting through fear

Dr Elena Touroni, a consultant psychologist and co-founder of The Chelsea Psychology Clinic in London, says that such behaviour is largely driven by fear.

"When people are in a heightened state of anxiety, and don’t fully understand for themselves what the measures mean and how they’re meant to protect them, they might perceive themselves to be in danger," Dr Touroni explains.

"When we feel vulnerable and frightened, we might engage in severe counter-attacking behaviours as a means of self-protection."

She adds, too, that public shaming is not behaviour unique to the coronavirus pandemic, but a feature of any period of crisis.

"The more heightened the feelings of vulnerability, the more we’re likely to see negative coping strategies used to manage those anxieties," adds Dr Touroni.

Lee Chambers MBPsS, Environmental Psychologist and Wellbeing Trainer, explains that this heightened state of anxiety can make it difficult for us to empathise with others, increasing the likelihood of being overly judgemental.

"During times of crisis, we can become overly focused on our worries and anxieties, and this leads us to not consider the reality of others, in turn leading us to be more likely to judge others and jump to conclusions," says Chambers.

Unclear instructions

However, Chambers also points out that "mixed messages" from the government may also be responsible for a spike in the policing of individuals.

"The government haven't been the quickest to get clear guidelines, and certain businesses have been quicker to set definitions than others," he says.

"Add to this the fact that some wording, such as "essential", creates a value judgement, and direct measures such as one exercise trip can cause others to actively count and record. There have been rising accounts of virus vigilantes, and this is undoubtedly in part to people having different definitions of what is essential."

Does shaming actually work?

Most experts agree that publicly shaming individuals rarely works - and, in fact, makes those shaming others less likely to take responsibility for their own behaviour.

"The majority of people who are responsible for actioning shaming tactics are trying to do the right thing... Unfortunately, this results in people taking less responsibility [for themselves] and being more likely to blame others," explains Chambers.

Shaming, he says, also taps into the way that humans are wired to "socially compare ourselves to others", making much of the social vigilantism we've seen more about the insecurity of the shamers than the behaviour of their victims.

"We are wired to socially compare ourselves to others. This can easily result in the neighbourhood dispute of 'I am taking this seriously, and they are flouting the rules'," says Chambers.

"And, in a time that's challenging, it is often those people who are feeling insecure who are more likely to shame others so that they can feel superior."

Ultimately, unless someone is genuinely breaking rules or causing trouble, public shaming will only make people defensive and unlikely to change their behaviour.