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A Japanese professor has produced evidence to show that computer games can have a bad effect on children. Many parents and grandparents have been saying this for years, but they were largely ignored, being regarded as technophobes. Parental worries about computer games often relate to their effect on their children's health and on their own social skills. They feel that they should be outdoors; getting exercise and enjoying the fresh air while playing with their friends. Since many of them usually play by themselves, they live rather isolated lives, with little opportunity to interact with other people. As a result, they may be very poor at communication. Parents are also worried in case the violence of many of the games will cause their children to become more aggressive and violent "themselves". This anxiety also applies to television, which often shows scenes of extreme cruelty.
Violence, cruelty and aggressive can be caused by ……..............…… .