"What is going on with young adults?" the Demographic Institute asks. "Family therapists," The New York Times tells us, "increasingly worry about the hidden emotional and psychological cost." This latest behaviorial and attitudinal problem, in a society that seems to spawn a new one each week, is something our grandparents would have considered entirely normal.

The problem is this. More unmarried young people are living at home with their parents. In 1970 47 percent of Americans between 18 and 24, some 10.6 million people, were living with their parents. In 1984, according to Census Bureau estimates, 54 percent of Americans in that age group, or 15.5 million young adults, were living with their parents. Once upon a time respectable young adults were expected to live with their parents until they got married. How can it be that the percentage of stay- at-homes has increased in an age of liberation from traditional restraints? How do these young people resist the blandishments of the singles apartment complex and Club Med?

As usual the experts have a number of hypotheses and prescriptions, which for all we know could be useful and even true. They say that the breakdown of traditional mores has helped: parents no longer think they can regulate their adult children's lives. The problem, they go on, is that their adult kids look for too much guidance and "don't have the same opportunities to fully develop their sense of individuality early in life." What was once considered the only respectable way for single adults to live has now become an avoidance of the real world.

We see cause and effect differently. The reason for the 46 percent rise in stay-at-homes is obviously the proliferation of earphones: this makes it possible for each household member to listen to his favorite television programs or "music" without disturbing others and starting fights. As for effect, are we not seeing that contact between the generations, that expansion of the nuclear family, that the psychologists who are worrying so much about stay-at-homes called for in last year's spate of articles about alienation in modern life? Our advice to everyone is to cheer up. If this is the worst problem social scientists can find this week, American society is doing better than we thought.