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One of the first questions our son Jim asks when a new movie comes out is “what’s it rated?” The more “adult” the rating, the more appealing the movie is to him: PG is the lowest rating he’ll even consider, PG-13 is better, and R is best. Since he’s only 14, we don’t take him to many R-rated movies, which is possibly what adds to their appeal.
But even PG-rated movies and TV shows still display an abundance of violence, and plenty of parents are happy to let their kids watch violent programming, especially if there isn’t any sex involved. We’ve reported on a lot of media violence studies on Cognitive Daily, (for a summary of the effects of violent media on youth, see here, here, and here), but it still came as a surprise to us that until now, there hadn’t been a brain activation study of children exposed to media violence.
A team led by John Murray has addressed that deficiency with a new experiment on 8- to 12-year-olds. They began by pre-screening 40 children by monitoring physiological responses to violent videos. They selected 15 children who showed similar responses to the videos: they were “accelerators,” whose heart rate increased when viewing violence. This would allow them to more easily compare brain responses in the second phase of the study.
These 15 children were monitored by an fMRI machine while they watched three different videos: scenes from the PBS children’s show Ghostwriter, a National Geographic nature show, and the over-the-top Stallone vehicle Rocky IV (albeit the edited for TV-version). To get a baseline level, the kids also spent some time viewing a figure X on a blue screen. Seven of the results had to be discarded because the kids moved around too much during the test, but the other eight fMRI scans provided significant results.
The fMRI scan provides a three-dimensional image of all brain activity. Since the brain is active in many different regions, the first thing the researchers had to do is isolate the activity that was different while kids watched videos. This was done by subtracting the values of brain activity while watching the fixed X from the activity while watching videos (Viol – Fix and Non Viol – Fix in the figure below). To compare violent versus non-violent videos, the researchers subtracted the non-violent brain activity from the violent brain activity.
This picture shows three different slices of the brain, viewed from overhead. The front of the brain is at the top of the images. Each row corresponds to a particular level of the brain, at a specified level (the z values indicate the relative distance from the center of the brain). For the most part, similar regions of the brain are activated, corresponding to the visual and auditory areas of the brain. But when we look at the difference between violent and non-violent scans, those areas are mostly cancelled out, and we are left with images showing the differences between viewing violent and non-violent videos.
The next set of images shows only the difference between the violent and non-violent videos, which was the focus of this study.
These images move progressively lower in the brain, showing differences at eight levels. The differences in the paralymbic area (marked Par) in the right hemisphere indicate that the violent videos used significantly more emotional processing. The posterior cingulate nucleus (PCg) was also activated, indicating emotional memory retrieval. The hippocampus (Hipp) activation indicates episodic memory storage, suggesting violent videos are more likely to be remembered. Finally, the right amygdala (Amg), the center of the fear reflex, was also activated.
Murray et al. argue that the activation of primitive regions of the brain such as the amygdala suggest that though children may be aware that violent media present no real danger, their brain’s response is identical to situations when a real threat is present. The amygdala is also active in impulsive aggressive individuals, suggesting that children may have little control over their response to violent media. Since long-term memory regions are also affected by violent videos, it’s possible that the effects of the videos extend beyond the viewing period.
Murray’s team cautions that their study results may not be generalizable. They studied only one type of violence, and didn’t compare it to an equally arousing nonviolent video, so perhaps the effects they observed are due to arousal rather than violence.
These results are certainly consistent with Jim’s behavior and preference for more violent movies, however. What they can’t explain is why, other than to see James Brown’s catchy anthem “Living in America,” so many people paid $7 to watch a film whose focus was two men pummelling each other while engaging in inane, monosyllabic dialog such as Dolph Lundgren’s “I defeat all man.”
Murray, J.P., Liotti, M., Ingmundson, P.T., Mayberg, H.S., Pu, Y., Zamarripa, F., Liu, Y., Woldorff, M.G., Gao, J., and Fox, P.T. (2006). Children’s brain activations while viewing televised violence revealed by fMRI. Media Psychology, 8, 25-37.
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