A new brain imaging study suggests that emotional responses to violence appear to diminish in teenage brains exposed to a stream of violent videos. However, some researchers have cautioned that the study does not necessarily tell us anything about what this means for the effect on aggressive behavior among teens.
The study's peek inside the brain used magnetic resonance imaging (MRI) to track brain activity as male teens watched and rated violent video clips. Its early results seem unlikely to calm the broader debate over what effect violence in TV, movies and video games has on people's thoughts and actions.
"In our study, any effect would be temporary, but in the course of life with repeated exposures to violent media, you are shaping your brain networks to be more accommodating to aggression," said Jordan Grafman, head of the cognitive neuroscience division at the National Institute of Neurological Disorders and Stroke in Bethesda, Md.
Not so fast, said Christopher Ferguson, psychologist at Texas A&M International University in Laredo who studies violent behavior and was not involved in the study. He argued that the study made a "huge number of assumptive leaps" about the brain-pattern responses and what they mean in terms of the boys being likely to carry out real-world aggression. [Related: Fight, Fight, Fight: The History of Human Aggression ]
"At first they got excited and then over time they grew bored," Ferguson said in an e-mail. "That's all this study really says."
The new research is detailed in the online edition of the Oxford Journal Social Cognitive and Affective Neuroscience.
Trying to read the brain
Grafman set up the study to help figure out which brain regions regulate aggressive behavior. Besides the MRI brain scanner, he also used finger electrodes to measure skin-conductance responses based on sweat.
The MRI scanner and electrodes tracked the responses of 22 boys, ages 14 to17, as they watched four-second clips of violent scenes from 60 videos. The boys also rated the violence in each clip by pressing one of two response buttons that rated it as more or less aggressive than the previous video.
Brain activity fell over time in response to each new violent video clip, and the most aggressive videos showed increased desensitization over time. Boys who had reported the most exposure to violent media each day before beginning the study also showed the greatest desensitization.
A brain region known as the lateral orbitofrontal cortex showed the most response. Grafman suspects that region codes for social rules of behavior, including rules for dealing with aggression.
Seeing other actions besides violence can also trigger an emotional response from the brain-any "provocative stimuli" that challenges what is considered normal behavior could lead to a similar reaction, Grafman told LiveScience.
If the emotional response to aggression gets dampened down over time, the brain's "brake" on aggressive behavior could ease up, according to Grafman.
Hold your horses
That may sound reasonable. But it's a mistake to say that this latest study supports the idea of the emotional dampening leading to acts of violence, Ferguson said.
"What does seem to happen is that as individuals watch more violent media, it generally becomes less startling over time," Ferguson said. "There is no evidence that this effect transfers to real-life violence."
He pointed out that the latest study did not measure how the boys reacted to watching real-life violence , and so there's no baseline for understanding the brain's emotional response to watching violent video clips.
The study also did not gauge the effect of violent video clips on the behavior of the boys-something study author Grafman readily acknowledges. He added that the boys did not show any immediate effects from the study, but did not rule out concerns for long-term exposure.
"Based on other aspects of the study, we might predict, under certain circumstances, that repeated desensitization to violence might lead to a greater likelihood of accepting, if not participating in, violent behavior," Grafman said.
Not playing games
Grafman suggested that the preliminary findings based on the reactions to violent video clips might also have implications for violent video games. Still, he cautioned that not all violent video games show repeated violence like the video clips in the study, and said many different games should be tested.
But it would be "deeply irresponsible" for now to generalize the study's findings to either video games or real-life behavior, Ferguson countered. And he has a point-the study was not designed to measure brain responses to either video games or real-life behavior.
"At this point, in fact, the best evidence suggests that video games, whether violent or not, have little to no role in youth violence or any other harm to minors," Ferguson said. "As video games have soared in popularity, youth violence has gone down, and youth involvement in civic involvement and volunteerism has gone up."
There's also a problem when scholars assume viewers can't tell fiction from reality, Ferguson said.
He referred to a class he teaches called Psychology of War , where he shows the World War II film "Saving Private Ryan,” which contains graphically violent scenes. His students often react blandly to the Hollywood violence, yet recoil in horror to video clips of seeing real deaths filmed during the 9/11 attacks on the World Trade Center in New York City.
Ferguson suggested that researchers need to take a hard look at any knee-jerk judgments about new media.
"Society elders wringing hands over 'youth today' and new media are nothing new they only look silly in retrospect," Ferguson warned. "Greek plays, dime novels, jazz music, Elvis Presley, Harry Potter, comic books — how many times do we need to dance to the same silly tune?"