Brain scans of children who saw dramatized violence showed a similar reaction to those who witnessed real violence, a scientist said in a book launched in Sydney.

Developmental psychologist Wayne Warburton of Macquarie University in Sydney said some key impacts of violent media on children are very well demonstrated in research.

"They include increases in the likelihood of aggressive behaviour, increases in desensitisation to violence and an increase in the overall view that the world is more scary and hostile than it really is," Warburton told The Daily Telegraph newspaper before the launch of the book he co-authored, Growing Up Fast and Furious.

Warburton said magnetic resonance imaging brain scans of children exposed to dramatized violence showed similar reactions to those who saw real violence.

"The brain isn't very good at differentiating between media and real-life situations, so we find very similar effects across all the main media -television, movies, video games and music."

Warburton said tests showed children who played violent video games had a heightened likelihood of aggression for up to 15 minutes after switching off the console.

"Over the long term it's just like eating fatty food - one hamburger won't kill you but there is a cumulative effect."

Warburton's conclusions come a day after the government announced an adults-only rating for video games. The move, to come in on January 1, will bar children from buying violent or sexual games and be a guide for parents.