Although computers can enhance people's ability to communicate, computer games are a cause of underdeveloped communication skills in children. After-school hours spent playing computer games are hours not spent talking with people. Ttherefore, children who spend all their spare time playing these games have less experience in interpersonal communication than other children have.
The assumption that children who do not spend all of their after-school hours playing computer games spend at least some of that time talking with other people is required by the argument.