THE big problem with joint custody,'' nine-year-old Josh told an interviewer in San Francisco, ``is that you have to remember where the spoons are.'' Living alternate months with each of his divorced parents, Josh, in his simple and poignant comment, touches on one of the deepest needs of children: a feeling of stability. As the institution of marriage comes through the instabilities related to high divorce rates, increasing numbers of women working, and lower birthrates, how are children affected?
How are children affected by parents discussing, arguing, fighting over splitting up? How are children affected by parents deciding not to have any brothers or sisters for the firstborn? How are children affected if their mothers and fathers both work long hours outside the home?
And how should the nation respond? ``If we create an incentive for people staying married, will we create a disincentive or a penalty for single parents and their children?'' asks sociologist Frank F. Furstenberg Jr. of the University of Pennsylvania.
In some ways, these are the most significant questions posed by the changes in marriage. They touch directly on:
Day care. The Congressional Budget Office estimates that by 1990, more than half the families with children under six years old will have both parents working. Although some excellent day-care centers are available, they are in short supply.
An Ohio mother tells of taking her one-year-old to look at a drop-in day-care center. She was shocked to find two young women in charge of more than 15 rambunctious children -- while in a nearby room five infants were left by themselves in cribs or swing chairs. Most of the children, she learned, were there from 7:30 a.m. to 6 p.m.
Schools. ``The nation has not yet confronted the question of how we deal with children who are not being attended by their families,'' says Ernest L. Boyer, president of the Carnegie Foundation for the Advancement of Teaching.
He predicts that ``we'll turn to the schools'' as ``the one public institution that America embraces.'' He forecasts a longer school day, an extended school year, and schooling starting at an earlier age -- ``simply as an accommodation to the new realities of the work patterns of parents and of economic circumstances.''
Children's activities. Drug use and crime rates appear to be linked to the numbers of adolescents in society -- and may be tied to the fact that as many as 7 million American children are left alone after school each day.
Some, of course, are engaged in constructive activities. And many are not out on the streets. But they don't always find it an easy adjustment.
Speaking to a congressional committee last year, a 10-year-old girl whose parents could no longer afford day care said, ``Some things scare me when I'm alone -- like the wind, the door creaking, and the sky getting dark fast.
``This may not seem scary to you,'' she told the committee of adults, ``but it is to young people who are alone.''
BASICALLY, the controversy over children and marriage in the US boils down to a single question: Who's in charge?
In the United States, the responsibilities for the children are widely defined as belonging to the private domain of the home -- rather than (as in some other nations) to the public domain of the state.
``That notion of somebody who loves you irrationally and who is prepared to devote inordinate energies to your upbringing is something that still depends on the traditional family,'' says Nicholas Zill of Child Trends, a research organization based in Washington, D.C.
``You cannot buy two loving parents on the market the way you can buy health care or an adequate shelter for an elderly person,'' he adds.
A. Sidney Johnson agrees. As former head of the Family Impact Seminar at George Washington University -- formed to monitor the effect of legislation on families -- he sees strengths in families that cannot be legislated.
``I think there's a real magic in families, certainly in families that are working,'' he says, adding that ``there's a love and a commitment, a flexibility and a genuine desire to help one another as much as you can without ignoring your own needs.
``And that's a thing of beauty, and I don't think it was designed by a scientist or by an engineer or taught in any school, but we all know families that are like that.''
Even the children tend to agree that the family is the focus for child care. A 1981 survey of 1,400 American teen-agers, sponsored by the Foundation for Child Development and the National Institute of Mental Health, showed that children, who still think of the mother as the primary provider of care, want her to be home.
Three out of 5 agreed that ``marriages are better when the husband works and the wife runs the home and cares for the children.'' Slightly more agreed that ``children are better off if their mothers do not work outside the home.''
But what about the families in which the parents cannot provide the bulk of the child care?
In particular, what about single-parent families?
These days, most of America's single-parent families arise not from the death of a spouse or an out-of-wedlock birth. Most arise from divorce. And their rapid growth, not surprisingly, has paralleled the growth in divorce.
Between 1970 and 1980, in fact, the number of married-couple families increased only 10 percent -- while the number of one-parent families headed by women increased 62 percent -- according to figures from the National Institute of Child Health and Human Development.
The impact on children is sobering -- more than 1 million children in the nation have been involved in divorce each year since 1972.
Frequently they are young children: Since the median duration of US marriages is seven years, it often means that divorcing couples who have children have young ones.
As the divorce rate levels off -- or, according to some measures, even begins to decline -- the formation of single-parent families should also slow. And, in time, there should be fewer children involved in divorce.
At present, however, the predictions are stark.
``The chances of the child born today ever living in a single-parent situation before he or she reaches the age of 16 are 6 out of 10,'' says Arthur J. Norton of the US Census Bureau.
In 1984, he adds, 1 out of 5 families with children under 18 was a one-parent family -- compared with 1 in 10 in 1970. ``These,'' he concludes, ``are very startling figures.''
EARLIER this month, 12-year-old Garrett Schulze of San Marino, Calif., surprised his parents with a telling comment. ``Gee,'' he said while watching TV, ``I hope when I get married I don't get divorced.''
``Our comment to him,'' his father recalls, ``was, `Well, Garrett, you don't have to get divorced. Just try to be understanding of the other person -- I think you can resolve your differences that way.' ''
Garrett has recently moved to a new school -- where, says his mother, only one other boy in his group has parents who are not divorced. ``They'd even seen a movie about [divorce] in class,'' his mother says.
``He was quite concerned about it,'' she continues. ``We keep telling him that it would never happen to us, because we love each other so much.''
Garrett, it seems, will not join the growing ranks of children whose parents are divorced. Yet even he is not unaffected by the shifting patterns of marriage. And if they touch him, how do they affect his classmates -- the children who have experienced divorce firsthand in their families?
RESEARCHERS in the field say the question of the effect of divorce on children is among the toughest.
Answers are notoriously hard to pin down -- since, as Professor Furstenberg says, understatedly, ``We cannot randomly assign some kids to divorce and other kids not to divorce'' and compare the two groups.
In addition, many researchers say, it is still too early to see long-term effects. Children born during the 1970s, when marriage was changing very rapidly, are only just beginning to emerge into adulthood.
But researchers tend to agree that the most pervasive effect of divorce on children is in the economic arena. ``There has been a growing trend toward child poverty,'' says Sheila B. Kamerman, a professor and co-director of crossnational studies in the Columbia University School of Social Work. That trend appears to be related to the trend toward divorce.
According to figures worked out by Stanford University Prof. Lenore J. Weitzman in the course of a 10-year study of divorce, American women typically experienced a 73 percent decline in standard of living in the first year after divorce -- while their ex-husbands experienced a 42 percent increase.
Meanwhile, only 13 percent of mothers with preschool children were awarded any alimony.
And since the divorced woman frequently keeps the children, the result of divorce is often an increase of economic hardship for the child.
Furstenberg, who has spent the last five years examining the research that deals with the consequences of divorce on children, concludes that divorce ``certainly disadvantages the kids, if for no other reason than that children of divorce are more likely to be poor, and poor children are less likely to advance educationally.''
But so far there appears to be little solid evidence that divorce invariably damages children emotionally and psychologically.
Research in those areas, Furstenberg says, is ``a very mixed bag.''
``Undeniably you do better to come from a stably married two-parent family than you do if you live in a single-parent family or a family where there is marital disruption and remarriage,'' he observes; ``but the differences are not very large or consistent.''
He notes, however, that the differences do appear greater for children whose parents divorce when they are young.
Jessie Turberg, a New York City marriage therapist, notes what she calls the ``sorely overlooked'' problem of depression in children of divorced families -- arising, she says, ``because they are constantly battling with a feeling that they are betraying one parent or the other parent'' and with a sense of a loss of family.
Says Dr. Zill of Child Trends: ``I think that the research evidence increasingly shows that the best thing for children's mental health is to grow up with both biological parents in a reasonably happy marriage.''
One point is certain: Divorce has become an easier option in the last 15 years. California inaugurated the nation's first ``no-fault divorce'' in 1970 -- allowing couples to divorce without having to prove that one or the other was guilty of adultery, desertion, physical abuse, or some other evil.
Since then, all states except South Dakota have adopted some form of no-fault divorce.
Most professionals interviewed for this series felt the change was essentially healthy -- since it helped reduce the number of oppressive marriages that would have simply lingered on.
Yet many observers also express concern that the prevalence of divorce has taken a serious toll on the nation. They believe that today too many couples are too easily persuaded to abandon their commitments to each other and to their children.
``Children do not need a mother and father to be ideally personally fulfilled,'' Zill says.
``Children need a reasonably stable and a reasonably harmonious marriage in order to thrive. It's clear that intense, persistent conflict within a marriage is bad for kids, but children can tolerate very well moderate conflict, even over extended periods of time.''
``We can't liberate children from the family,'' Zill concludes, ``unless we'reprepared to accept a very radically different notion about how children should grow up.'' Third of five parts. Tomorrow: Will the US follow Europe's lead?