When equal custody is law, who gains?

Ever since Armin Brott of Oakland, Calif., was divorced seven years ago, he and his former wife have shared equally in the care of their two daughters.

One week the girls, now 10 and 14, spend Monday and Tuesday with him, then Wednesday and Thursday with their mother in nearby Berkeley. On Friday they return to Dad's for the weekend, followed by Monday and Tuesday at Mom's. And so it goes through a two-week cycle.

This kind of postdivorce sharing remains relatively rare. But beginning July 1, it will become more common in Iowa. That's the day the state institutes what some family experts are calling the country's first true shared-parenting law. It gives judges power to award joint legal and physical custody if a parent requests it. Judges who refuse must explain their reasons.

Although not everyone agrees that joint custody is best in all cases, some fathers in Britain are hoping for a law similar to Iowa's. Last Friday, nearly a thousand members of a radical fathers' group, Fathers 4 Justice, paraded through London to call attention to what they say is unfair treatment of fathers in custody issues. Members also prepared a document for Parliament calling for family-law reform. Their proposals include a presumption that parenting time will be shared 50-50.

Some joint physical-care arrangements, like Mr. Brott's, are 50-50. Other parents work out 60-40 time splits, or even 70-30. Currently, most children live with their mother after a divorce and see their father on weekends. In 2 million families, the father is the custodial parent.

But what sounds good in theory in this new domestic landscape can become challenging in practice for some families. Critics charge that constantly shuttling children back and forth between two homes can create instability.

"It's destructive of discipline," says Diane Dornburg, chair of the Iowa State Bar Association's family-law section. "It can generate the feeling that the child doesn't belong to either parent."

One member of the Iowa bar, she notes, calls the practice "making the child into a calendar." Her own critical term is "equitable distribution of children." Although parents get equal time with the child, she says, "you're treating the child as a possession to be shared equally. How does that affect the child?"

Trial judges also dislike joint physical custody, Ms. Dornburg finds, because the arrangement is not permanent. If one parent has a new spouse, a new job, or a new house, "that can throw off the balance that created the arrangement in the first place."

Yet such schedules can succeed, Dornburg acknowledges, when parents get along and when both focus on what's best for their children. They must communicate, cooperate, and maintain day-to-day routines.

Some psychologists also caution against rigid 50-50 splits between households. Brenda Payne, a child psychologist in Iowa City, Iowa, emphasizes the need to consider what is developmentally appropriate for a child. She tells of one couple who divorced when their baby was very young. The parents lived in different states but worked out a 50-50 time split.

"They couldn't figure out why the infant wasn't doing well," says Dr. Payne. "It wasn't eating and was crying all the time. It turned out to be pretty much a disaster for the child."

Joint physical care can also be difficult during toilet training, Dornburg says. "For a young child, it can be disruptive to wake up in a different bed and have to figure out which house am I in, where's the potty, and how do I get there from here?"

Shared custody can become less practical and less necessary in adolescence. Even in intact families, Payne notes, teenagers often spend little time with parents.

When Robert Franklin's son and daughter were young, they spent a week at a time with each parent, a schedule that worked well for them. By the time the children had reached sixth grade, says Mr. Franklin, of Boston, the couple abandoned that and instead based decisions about living arrangements on what best met the children's needs.

Family activists see the Iowa law as part of a larger move to change family courts on both sides of the Atlantic. "Noncustodial parents are becoming more vocal, they're becoming more organized, and they're beginning to demand accountability from elected officials," says Michael McCormick, director of the American Coalition for Fathers and Children.

In Massachusetts, supporters of shared parenting are gathering signatures to get a non-binding public-policy question on the ballot in November. Voters will be able to indicate whether they favor joint physical custody after divorce, except in cases where parents are unfit or violent.

"It's basically a philosophy of having two real parents instead of one parent and a visitor," says Ned Holstein, a physician and president of Fathers and Families in Boston. "It's a reasonable solution to the problem of taking care of children after divorce."

That's not necessarily true if the divorced parents don't get along, says Richard Warshak, a clinical psychologist in Dallas and author of "Divorce Poison."

"If the parents are absolutely hostile to each other, and the changeovers [from one house to another] are being used as an excuse to get out some anger at the other parent, that puts the kids in a terrible position," he says.

Still, Dr. Holstein thinks the Iowa law marks the beginning of "the most effective improvement for children of the last 30 years and the next 20 years."

Iowa Gov. Tom Vilsack calls it the most significant bill he has signed this year.

State Rep. Dan Boddicker (R), the bill's sponsor, has no illusions that the path ahead will be smooth. "It'll take a while for this to be fully implemented," he says. "There's a lot of reluctance in the courts to take this seriously." Even so, he adds, "I'm hoping it will lead to good things in Iowa, and that other states will follow."