The supposed dangers of familial nudity.

A court commissioner has ordered Britney Spears to undergo random drug and alcohol testing as well as meet with a parenting coach for eight hours each week. The pop star has been excoriated for her parenting blunders; she reportedly feeds her children junk food, whitens their teeth, and, according to a former bodyguard, regularly parades around them in the nude. What effect does parental nudity have on a young child?

If the kid is younger than 3 years old, it's probably harmless. At least, this is what many adolescent psychiatrists believe; there have been few rigorous studies of the subject. Very young children won't notice anything odd about a parent who prances around the house in the buff. Likewise, babies who breastfeed at 12 months are physically intimate with their mothers and don't think twice about it. Chances are good that a 2- or 3-year-old won't form any lasting memories of seeing his parents in their birthday suits.

Seeing your parents au naturel can be confusing for older kids who are more curious about bodies and sexuality. A child might wonder why a parent's genitals look different from his own; he might feel inferior by comparison, or jealous; and he might be a bit frightened of the size and hair. Too much exposure might also overstimulate a child, stirring up sexual excitement along with Oedipal anxiety.

One Stanford University study from the 1980s found that children in the United States develop a sense of modesty somewhere between the ages of 4 and 8 (and sooner for kids with an older sibling to emulate). Researchers questioned parents in more than 400 California households about what they observed of their children's development and followed with updates over a three-year period. In this age range, it turns out, kids start to learn the cultural norm for privacy—this is when little boys stop going to women's restrooms with their mothers, or little girls no longer want their fathers to give them baths.

Bonus Explainer: What will Britney learn from her "parenting coach"? How to set goals and solve problems relating to her kids. Parent coaching sprang up as a vocation just a few years ago, so there aren't very many programs that accredit professionals. Most coaches will charge anywhere from $40 to $125 a session to help parents do anything from finding a nursery school to working with new stepparents or dealing with sibling rivalry. In theory, a trained outsider can help parents find new ways to handle problems, or at least break old patterns; frustrated parents apparently tend to revert to the parenting style that they grew up with.

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Explainer thanks Elizabeth Berger, Peter Chubinsky, Gloria DeGaetano of the Parent Coaching Institute, Caron Goode of the Academy for Coaching Parents International, Chike Nwankwo, and Alvin Rosenfeld of Harvard Medical School.