New research published in Science Magazine over the ThanksGiving period sheds new light on the impact of watching violent scenes in television shows, the news, and movies.
When you allow yourself, or a child, to watch violent media images, you change the functioning of the brain and shift it into survival mode , also knows as the fight or flight, and stress response.
In the first experiment, MRI equipment was used to monitor blood flow in the brains of 80 adult volunteers while they watched scenes featuring "extreme male-to-male aggressive behavior and violence in front of a crowd". The researchers also took samples of the participants' saliva to measure changes in stress hormones levels to see if there was a hormonal response to the violence.
In a second experiment, the researchers also used chemicals to block the production of certain stress hormones while the volunteers watched violent scenes to see how it affected the participants' brains.
The researchers noticed that when participants watched violent images, networks of nerve cells started to rapidly reorganize themselves throughout the brain: the participants' brain function was changing in response to what they were seeing on the screen. The volunteers' attention was reorientated, their perceptions were heightened, and their autonomic nervous system became highly active, all of which are indicative of the stress response.
What if you don't get frightened by violent images?
Even if you tell yourself that the fighting you saw in a movie, news broadcast, or TV show ddn't scare you, the stress response, which is governed by your unconscous mind, works fast. It is an active part of everything you do and is works like a virus checker, running quietly in the background of your mind, always alert and checking for threats.
When you are engrossed in watching a TV show, movie, or news footage, your unconscious sees the violent images and doesn't know they are on a screen; your unconscious believes you are right there in the action. Seeing others get hurt triggers your unconscious to want to fight or flee to avoid injury, pain, and the potential for death because it thinks that you may be the next target of the serial killer, soldier, or alien who is being violent. The fight or flight response results in the heightened perceptions, reorientated attention, and nervou system stimulation observed in the volunteers.
The wider implications of this research are that watching domestic violence between parents, being subjected to physical punishment, and seeing gory photographs  in newspapers and online may also shift a child and adult into fight or flight (survival) mode.
I suspect that people who have experienced physical violence, whether as a child or adult, are more susceptible to experiencing greater levels of stress when they see on-screen violence later in life.
Watching violent media content harms a child's psychological development, and is also harmful for adults. A person who is exposed to survival stressors such as:
- physical violence to themselves or to a loved one [a.k.a. punishment],
- insufficient food, water, sleep,
- or deprived of one-on-one loving attention)
has their perceptions changed for life, unless they seek psychological support to change their perceptual filters; they see the world as an unsafe, potentially threatening place, instead of somewhere they can love and be loved, thrive, and contribute meaningfully to humanity.
After reading this article, why anyone would allow a child to view violent media and gory images, knowing full well that it has a strong likelihood of psychologically harming them for life? In my opinion, the view of 'let the parent decide' is an excuse for ignorance and denial.
Why would you, as an adult, continue to watch violence when you know that it makes you more stressed, changes your perceptions to the world towards it being unsafe place, and and shifts your brain and physology into fight or flight mode. People who are more stressed also have higher incidences of disease.
Watching the late night news will never be the same again.
 Hermans, E. et al. (2011). Stress-related noradrenergic activity prompts large-scale neural network reconfiguration. Science, 334, 1151-1153.
 Zald, D. H. (2003). The human amgydala and the emotional evaluation of sensory stimuli. Brain Research Reviews, 41, 88-123.