Street robbers often carry out their vicious crimes to boost street cred or are motivated by a sheer desire to fight, according to a report today.
The study includes interviews with 120 offenders - a third of whom had been arrested more than 50 times - and found that street culture can be a far more important factor in such crimes than financial gain.
It is published the day after Adele Eastman, the fiancee of murdered lawyer Tom ap Rhys Pryce, told how she believed his killers were "trying to play the big man".
In a statement read to the judge presiding over the sentencing of Donnel Carty and Delano Brown at the Old Bailey, she said: "Greed fuelled Carty and Brown's attack on Tom but it is obvious, particularly from the trademark injury which they inflicted on his left leg, that they were also trying to play the big man."
She added: "I despair at their deeply misguided sense of logic - because it is not a man who attacks a defenceless person with a knife or any other weapon, or hunts victims down in a pack, it is the complete coward."
Today's research, funded by the Economic and Social Research Council, claims that previous attempts to explain the rise in violent street crime placed too much emphasis on offenders' desire for cash or property such as mobile phones.
Mr ap Rhys Pryce's killers stole just an Oyster (travel) card and mobile telephone from their victim.
Interviews with offenders reveal that some found robbery to be a pleasurable activity in its own right, with one offender saying he was addicted to it, the study said.
"I was more addicted to robbing than I was to drugs. Just get a funny feeling when I go out robbing."
The authors report that one element in the excitement felt by the violent offenders comes from overpowering the victim and obtaining dominance.
"It's for the fun. 'Cos the point of street robbery is to get them to fight back, innit?", said one criminal.
And sometimes the theft was just an afterthought, with the crime prompted by "anger and the desire to start a fight", the report says.
"I picked a fight with someone on the street. They were the first people I come across," said one interviewee.
"I started hitting one of them and calling him names and said 'What are you looking at?' and stuff like that.
"Then I can't remember how, but I started hitting him and then I just jumped on him."
The average age of those interviewed was 26. A third said they were involved in gangs or criminal groups.
More than a quarter (28 per cent) carried firearms and an additional 35 per cent carried some other weapon, usually a knife.
In all, 92 per cent had used illegal drugs.
Financial gain was a common motive for many offenders, the report says, with cash made from crime often spent on "non-essential, status-enhancing" items.
Professor Trevor Bennett, director of the University of Glamorgan's Centre for Criminology and one of the authors of the report, said: "The decision to commit street robbery can be explained in part by particular characteristics of the street culture.
"This finding is important, because British research has tended to explain robbery in terms of rational choice and to focus instead on the role of cost-reward calculations.
"Our research suggests that any explanation must primarily take into account cultural factors associated with life on the street."
* Eighty-nine males and 31 females serving sentences for violent offences in prisons and young offenders' institutions in England and Wales, were interviewed;
* A total of 36 per cent had been arrested more than 50 times, 17 per cent between 25 and 49 times and 30 per cent between 10 and 24 times.