Influence of violent media on children and adolescents.

In their review on the influence of violent media on children and adolescents, Kevin Browne and Catherine HamiltonGiachritsis (Feb 19, p 702) raise the question of why children and adolescents are more susceptible to media violence than adults. The effects of television are best understood in terms of rote learning—ie, by the brain digesting thousands of examples and thereby shaping synaptic connections, a process usually referred to as neuroplasticity. Lundborg and Rosén made the link between age and the speed of synaptic change quite clear. They plotted the results of a test on tactile gnosis after peripheral nerve damage against age and found a striking reduction in plasticity during the second decade of life. Physiology and neuroscience can augment correlational data on several public-health effects of screen media. For example, the correlations between television viewing at age 1 and 3 years and attention deficit disorder at first grade, and between television watching at age 4 and 5 years and reading in third grade can be explained by a child’s need to process clear-cut spatiotemporal signals to form proper representations of objects and the outside world. If a 2-year-old spends 2 h per day watching television, a substantial part of his or her experience will consist of degraded input—ie, sounds and vistas that correlate poorly, let alone have the added benefit of touch, smell, taste, and visual depth. Such impaired input can only lead to impaired representations, and such impairment will increase the risk of attention dysfunction and dyslexia. To take another example, Hancox and co-workers found a clear correlation between television viewing at age 5–15 years and obesity in adulthood. Even though they were able to infer the direction of effect (does television make you fat or do fat people watch television?) from the prospective longitudinal Correspondence