In many parts of the world, a young person's husband or wife is chosen by the person's parents. In the United States, the choice is usually made by the young people themselves. A few people now pay private companies to help them in their search for the right husband or wife. Such a company collects a great deal of information about each man and woman who is interested in marrying and puts the information on a card, which is called an IBM card All the cards are then classified (分类) by a computer, a machine which organizes the cards into groups. The theory is that such a machine can make the best decision about matching the right, nab with the right woman because machines are not influenced by emotions(情感). Mr. Walker and Miss Brown are such a couple. When they first, net, they did not have much to talk of since everything was written on their cards. They are so perfectly matched that they seem to have everything in common. For instance, they have the same interests, future plans and even living styles. This passage is mainly about _______.