Sending abusive messages to people over the internet - or ‘trolling’, as it is known - has made headlines over the past few days following reports of vitriolic abuse aimed at the parents of missing Madeleine McCann.

It was revealed last week that police are investigating people using the anonymity of the web to target the Rothley family, whose three-year-old daughter went missing in Portugal in 2007.

As reported in the Mercury, another tragic twist came on Sunday when Brenda Leyland, of Burton Overy, who is alleged to have tweeted 4,220 offensive messages to the McCanns, was found dead in a Leicestershire hotel room.

Professor Brian Brown, of De Montfort University, specialises in interpreting “human experience” across a variety of different disciplines, including education and the mass media. 

The Mercury asked him why some internet users chose to troll others online.

“I think the subject of internet trolling, particularly with the extraordinary growth in the everyday use of social media sites such as Twitter and Facebook is an interesting but complex one,” he said.

“There has been very little research into trolling, but a recent Canadian study, published in Personality and Individual Differences, the journal of the International Society for the Study of Individual Differences (ISSID), makes interesting reading.

“What they did was to survey a few thousand internet users asking them about their behaviour and interactions while online.

“It discovered that many people who troll, which they define as the practice of behaving in a ‘destructive, or disruptive manner in a social setting on the internet with no apparent instrumental purpose’ share similar characteristics.

“Many show traits of narcissism, Machiavelli-like manipulation, psychopathy, sadism and other antisocial personality disorders.

“Although these were essentially self-reporting questionnaires, the answers can be very revealing.

“It seems a lot of people who troll take great pleasure in manipulating others and have a very well developed sense of their own importance.

“But often, in reality, they are quite vulnerable individuals themselves, probably very isolated who don’t have much positive interaction with people in the real world, and who spend most of their time online.

“The cloak of anonymity afforded by the internet can be quite empowering for these people.

“Real life is difficult – finding a good job and keeping it is hard; raising a family is hard; relationships are difficult, especially romantic ones that quite often don’t go the way we would want.

“However, on the internet people can create their own identity anew, often several ones, where they can compensate for their feelings of inadequacy. And whilst they wouldn’t say boo to a goose, face-to-face, they can indulge their alternative persona online.

“The anonymity of the web means that, more often than not, they will not be exposed.

"We can see this extreme behaviour in other forums, for example, when someone enters a football stadium or wrestling arena, the rules of engagement are different, and some of the interaction between fans, and performers, can be viewed as extremely abusive.

“Similarly, with incidents where someone is threatening to commit suicide from a building or bridge and crowds gather, you sometimes hear reports of them shouting, ‘jump! jump!’, to the individual.

“Research has suggested that this is more likely if it is dark and the crowd is large.

“As far as targeting celebrities, many people feel they are fair game, as does the tabloid media.

“And when you hear of famous people shutting down their Twitter accounts, for example, after just a few days, due to abuse, those responsible realise how their cruel behaviour can have a powerful effect.

“They can make someone cry, make them upset, get them to react.

“This almost instantaneous result feeds and reinforces the antisocial behaviour and there is instant gratification.

“They say, ‘Hey, I am powerful, look what I’ve done’.”