The mental skills developed through playing computer games do not contribute significantly to children's intellectual development. Passive activities such as watching television and listening to music do not hinder the development of communication skills in children. Formal instruction contributes little or nothing to children's acquisition of communication skills. 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.
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 argument depends on which of the following assumptions?