(CNN) -- "Playing doctor" and "I'll show you mine if you show me yours" are common rites of passage in childhood sexual behavior, according to the experts.
If so, did actor and screenwriter Lena Dunham do anything wrong when, at age 7, she peered between her 1-year-old sister's legs and spread her vagina to see if it looked like hers? What about when she tried to bribe her younger sister with candy for kisses -- behavior she likened to that of a "sexual predator" -- or when she touched herself while the two girls shared a bed?
The Internet has been pondering these questions since National Review correspondent Kevin Williamson accused Dunham of sexually abusing her sister as a child. He based his argument on passages in Dunham's memoir, "Not That Kind of Girl," including ones in which the author describes the episodes above.
Williamson, a known provocateur who once argued that women who had abortions should be hanged, pinned much of the blame on Dunham's parents -- whom he called "self-styled radicals" who failed to enforce "even the most lax of boundaries."
He accused them of enabling behavior "that would be considered child abuse" in some places.
Low blow or not, Williamson's allegations prompted the question: When does childhood curiosity cross the line into inappropriate, abusive behavior?
The resulting flurry of tweets, op-eds and blog posts about Dunham's behavior would have you believe it's a black and white issue. While columnists debate whether the "Girls" creator and star should be stripped of her feminist credentials, and Twitter activists urge HBO and Planned Parenthood to #DumpDunham, experts say the truth is more complicated because we don't know every detail of the sisters' relationship.
What matters more than what Williamson and others make of their childhood relationship is how Dunham's sister, Grace, responded to the events as a child, how their parents addressed them in the moment, and how they continue to affect the younger sibling, now 22.
I told a story about being a weird 7 year old. I bet you have some too, old men, that I'd rather not hear. And yes, this is a rage spiral.— Lena Dunham (@lenadunham) November 1, 2014
And by the way, if you were a little kid and never looked at another little kid's vagina, well, congrats to you.— Lena Dunham (@lenadunham) November 1, 2014
There's no way to know any of that for sure -- even in her book, as Williamson points out, Dunham claims to be an "unreliable narrator." But experts say the most useful takeaway for parents is the importance of reinforcing from an early age their kids' right to privacy along with bodily respect for others.
Though the Dunham sisters' age difference of six years could raise red flags, experts say the absence of evidence of a pattern of coercion or use of force make the instances cited in Williamson's article, "Pathetic Privilege," seem less troubling than he made them out to be.
At the very least, it's not the kind of behavior that warrants branding a pre-pubescent Lena Dunham a child abuser. Nor does it mean that such behavior, even if age appropriate, won't have adverse affects on those involved.
"Parents need to recognize that many children will engage in sexual exploration with siblings or friends of their own age or younger. Although these behaviors can be of concern, it is important to understand that they may not, in itself, indicate a tendency toward sexual aggression or abuse," said New York psychotherapist Lisa Brateman, who counsels couples and families. (Neither she nor the other medical professionals quoted in this story have treated the Dunhams.)
"It can be difficult to tell the difference between age appropriate sexual exploration and warning signs of harmful behavior," Brateman said. "Therefore it is imperative to teach your children what is appropriate behavior."
Appropriate behavior depends on age, changing as children learn society's rules and develop self-control. Very young children are naturally immodest, It's natural for them to express curiosity about bodies by touching themselves and others in public, or asking about the differences between girls and boys.
As children get older and their awareness of acceptable behavior increases, they become more modest and seek out privacy while becoming more curious about adult sexual behavior, especially in puberty. For more information about age-appropriate behavior, check out the National Child Traumatic Stress Network's guidelines for parents on sexual development and behavior in children
Such behavior poses a risk when it is clearly beyond a child's developmental stage, like a 4-year-old attempting sexual penetration, said sociologist David Finkelhor, Director of the University of New Hampshire's Crimes against Children Research Center.
Parents should also look out for patterns of aggression, physical force or coercion at any age, such as preoccupations with touching breasts or public exposure, especially if the behavior continues with age.
What matters most in these circumstances is how parents address these transgressions, without shaming children or making them feel guilty, he said. The act is bad, not the child.
"When children don't have answers to questions on their minds, that's when they'll take matters into their own hands," he said. "It's important to have these conversations early in childhood, and often."
Lena Dunham released a statement Monday saying she was dismayed by the interpretations of her book and that her sister had approved of everything published about her.
heteronormativity deems certain behaviours harmful, and others "normal"; the state and media are always invested in maintaining that— Grace Dunham (@simongdunham) November 3, 2014
As a queer person: i'm committed to people narrating their own experiences, determining for themselves what has and has not been harmful— Grace Dunham (@simongdunham) November 3, 2014
Grace Dunham did not respond to CNN's request for comment, although she said on Twitter, "I'm committed to people narrating their own experiences, determining for themselves what has and has not been harmful."
Many critics cited the age difference between the sisters as evidence of Lena Dunham's inherently abusive behavior, a valid argument because research shows that the age differential matters.
As a rule of thumb, if there's more than five years between children there's a "fairly reasonable likelihood" that the older child has more power than the younger one, said Florida clinical psychologist Steve Gold, Director of the Trauma Resolution Integration Program at Nova Southeastern University's Psychology Services Center.
That power differential could be used to manipulate or coerce the younger person into unwanted activity, which crosses the line into dangerous territory, he said. It's hard to know what's going on, though, unless a child feels comfortable bringing their concerns to an adult -- again, emphasizing the importance of open communication.
"Ultimately the deciding factor is to sit down with the younger child and get a sense of whether they feel they're being pressured, uncomfortable or coerced; and, to do it in way that makes clear to the child they're not at fault," said Gold, whose research focuses on adult victims of childhood sexual abuse.
"It's important when a child does step forward that adults are prepared to listen carefully and not to assume that they're lying or making it up and listen closely and take the child seriously, and be prepared to take effective action to see to that it stops," he said.
"Right now, we're teaching children to tell someone, but basically putting the responsibility on the child to make it stop and that can be damaging if (we're) not teaching adults the importance of taking decisive action," he said.