In 2007, a British school teacher in Sudan received a jail sentence under Sharia law because she allowed her pupils to name a classroom teddy-bear ‘Muhammad’. The day after the sentence was announced, more than 10,000 people took to the streets of Khartoum demanding the teacher’s execution for blasphemy. While alternative explanations existed – the name Muhammad was chosen by children’s voting, it is a popular male name in Sudan – the teacher faced such disproportionate hostility because some people interpreted her actions as an insult to their whole group.

In 2014, a production team from the British TV series Top Gear was forced out of Argentina by angry protesters offended by the licence plate on one of the show’s cars. It read ‘H982 FKL’, which the Argentinians saw as a sneering allusion to the 1982 Falklands war with the UK. Naturally, this could have been a coincidence or a mistake, but it was interpreted as an insult to Argentina, and followed by retaliatory hostility.

In these examples, those who felt that their group had been insulted must have held the group in high esteem. But not all who hold their group in high esteem feel insulted and retaliate after real or imagined threats to their group’s image. So why do some feel that their group was insulted while others do not? And why do some feel that their group has been insulted even when no insult was intended and alternative explanations have been offered?

Research from my PrejudiceLab at Goldsmiths, University of London shows that people who score high on the collective narcissism scale are particularly sensitive to even the smallest offences to their group’s image. As opposed to individuals with narcissistic personality, who maintain inflated views of themselves, collective narcissists exaggerate offences to their group’s image, and respond to them aggressively. Collective narcissists believe that their group’s importance and worth are not sufficiently recognised by others. They feel that their group merits special treatment, and insist that it gets the recognition and respect it deserves. In other words, collective narcissism amounts to a belief in the exaggerated greatness of one’s group, and demands external validation.

Collective narcissists are not simply content to be members of a valuable group. They don’t devote their energy to contributing to the group’s betterment and value. Rather, they engage in monitoring whether everybody around, particularly other groups, recognise and acknowledge the great value and special worth of their group. To be sure, collective narcissists demand privileged treatment, not equal rights. And the need for continuous external validation of the group’s inflated image (a negative attribute) is what differentiates collective narcissists from those who simply hold positive feelings about their group.

In Turkey, collective narcissists enjoyed Europe’s economic crisis because they felt offended by their country being denied membership of the EU. In Portugal, collective narcissists rejoiced in the German economic crisis because they felt their country was slighted by Germany’s position in the EU. Stretching the definition of intergroup offence even further, collective narcissists in Poland targeted the makers of the Polish film Aftermath (2012) for telling the story of the Jedwabne massacre of 1941 in which villagers set fire to their Jewish neighbours, and then blamed the Nazis. Even a petty transgression such as the film’s lead actor joking about the country’s populist government (whom Polish collective narcissists support) was met with threats of physical punishment and online abuse.

When their own group is involved, collective narcissists have no sense of humour. They are disproportionately punitive in responding to what they perceive as an insult to their group, even when the insult is debatable, not perceived by others, or not intended by the other group. Unlike individual narcissists, collective narcissists cannot dissociate themselves from an unpopular or criticised group. Once their self-worth is invested in the greatness of their group, collective narcissists are motivated by enhancing their group rather than themselves.

My team researched collective narcissism as a characteristic that pertains to an individual. We believe that there will always be a proportion of people in any given population who meet the criteria. But collective narcissism can also seize an entire group, resulting in seemingly sudden and unprovoked outbursts of intergroup rage or prejudiced reactions towards minority groups. We believe that collective narcissism is most dangerous as a group syndrome – when the belief that the righteous group is not given its due acknowledgement becomes shared by the majority of group members and becomes a dominant narrative about the group’s past and present.

Such collective narcissism is so toxic it explains phenomena such as anti-Semitism and perhaps even two world wars. It might explain the 2015 terrorist attack on the headquarters of Charlie Hebdo, the French satirical weekly that published controversial caricatures of the prophet Muhammad. Recent research by Katarzyna Jaśko and her colleagues at the National Consortium for the Study of Terrorism and Responses to Terrorism at the University of Maryland, College Park demonstrates that collective narcissists in radicalised social networks are ready to engage in political violence and terrorism.

But collective narcissism explains political behaviour in established democracies, too. Recent research indicates that national collective narcissism was implicated in voting behaviour in the Unites States: apart from partisanship, this was the strongest factor predicting voting for Donald Trump in the 2016 US presidential election. Collective narcissism also explained the Brexit vote in 2016, because it predicted fear of immigrants and foreigners.

Recently, scientists at the University of Pennsylvania scanned narcissists’ brains with fMRI and found physiological evidence that their experience of social rejection was particularly hurtful, despite their denials to the contrary. This is so important because other new findings show that people derive emotional pleasure from responding to rejection with aggression. It is likely, although it remains to be confirmed, that collective narcissists feel similarly distressed when their group is criticised, rejected or otherwise undermined. They can be particularly tempted to use aggression to reduce their distress.

Can we find alternative ways of reducing the link between collective narcissism and a tendency to react with retaliatory intergroup hostility to trivial acts and events? Answering this question is the topic of our ongoing research for my team at Goldsmiths. If we could learn to deactivate the hostility felt by people who score high on the collective narcissism scale, we might also learn to defuse and de-radicalise collective narcissistic groups.