Once upon a time, there was just one voice of authority on how to raise children, and his name was Dr. Benjamin Spock.

Those days are gone.

Starting in 1946, a whole generation of baby boomers were raised on advice from the avuncular pediatrician, whose book “Baby and Child Care” sold nearly 750,000 copies the first year alone — without advertising. But ask Jonah Davenport, father of a 2-year old, if he’s ever read Dr. Spock, and the Washington, D.C., resident can scarcely stifle a guffaw.

“Naah,” says Mr. Davenport, 38, an early childhood education teacher.

He is seconded, somewhat, by Tricia Flock, 36, of McCandless.

“I’ve heard of him,” the mother of a 2-year-old and a 4-month-old says of Dr. Spock, “but I didn’t think he was for me. He sounded as though he’d be somewhat outdated.”

What about Penelope Leach and T. Berry Brazelton, the popular parenting authorities of the 1970s, ’80s and ’90s? “I’m afraid not,” she said.

All three still have books in print — a revised edition of Dr. Spock’s tome is coming out in 2011, and his legacy lives on in The Dr. Spock Co. and its Web site, Drspock.com. But his influence, and that of Drs. Leach and Brazelton, has clearly faded as a new generation of parents grapples with the age-old questions of how to soothe a baby’s crying, whether to bottle feed or breast-feed and how to handle tantrums.

If anything, it’s the era of Too Much Information, a lot of it conflicting — and not just from the hundreds of books, Web sites and even cell phone applications that distract restless toddlers. A recent New York Times piece highlighted the burgeoning popularity among parents of dog trainer Cesar Millan, a.k.a. “the dog whisperer” — use dog training concepts to raise your kid — and Time magazine’s Nov. 20 cover story focused on “The Growing Backlash Against Overparenting” with the pendulum swinging toward “slow parenting” and other less fraught ways of bringing up baby.

“Some days I think I’m doing everything right, and some days I have no clue,” said Ms. Flock, who notes that at a bimonthly gathering of preschool mothers at Northway Community Church, “we talk a lot about what we should or should not be doing. Should you do baby sign language or not? Should we spank or not spank? There are just so many people out there saying you should do this, you should do that, it makes you really nervous sometimes.”

Who’s to blame for this cacophony of confusion? Who else but baby boomers, driven, obsessed, hungry for information about their-children-as-projects, even as mothers flooded the workplace and families moved around the country, cutting themselves off from relatives and longtime neighbors who would have been an extra pair of hands or a soothing voice in times of stress.

“One of the big shifts in the last generation was the atomization of the nuclear family, which means we are cut off from age old wisdom of mums and grandparents to tap into,” notes Carl Honoré author of 2004’s “In Praise of Slowness,” and of a new book “Under Pressure: Rescuing Our Children from the Culture of Hyper-Parenting.”

And if anything, he contends, the books that promise to fill that void end up making parents even more unsettled.

“I’m not against advice, it’s useful to have it, but we’ve become advice junkies,” Mr. Honoré said in an interview from his London home, “constantly searching for the guru of the day and the expert of the moment before deciding what to do, rather than looking at our own experiences and relying on the people around us.”

Anxiety over child rearing has been with us since the dawn of the industrial age, writes Ann Hulbert in her 2003 book “Raising America: Experts, Parents, and a Century of Advice About Children.” The pendulum, she adds, has always swung from chilly to warm and fuzzy: In the 1920s and ’30s, behavioral scientist John Broadus Watson warned parents not to hug their children too much; Dr. Spock told postwar parents not only to hug them, but to “trust yourself. You know more than you think you do.”

As late last century’s culture wars intensified, child-rearing became almost politicized, with attachment-parenting-bonding guru William Sears on one end of the spectrum and strict disciplinarians John Rosemond and James Dobson on the other.

The notion of one omniscient voice, however, seems as last century as Walter Cronkite.

“I couldn’t really say which books are most popular among my friends. They all read different things. I also really like two Web sites — but I can’t remember their names,” added Christine Liberati, 32, of Ben Avon, with a laugh. Ms. Liberati, the mother of a 6-month-old, relied on “What to Expect the First Year,” by Heidi Murkoff, which leads the Barnes & Noble list in the infant and toddler category.

The rising rock star these days, however, seems to be Dr. Harvey Karp, a Los Angeles pediatrician and author of “The Happiest Baby on the Block: The New Way to Calm Crying and Help Your Newborn Baby Sleep Longer.” After his book came out in 2002, devotees (Madonna, Pierce Brosnan among others) dubbed him the “baby whisperer” because of his ability to calm a screaming infant by administering the “Five S’s”: swaddling, positioning the baby on his stomach or side, making shushing sounds similar to those in utero, swinging the baby and having him suck on a pacifier or breast.

Today, Dr. Karp is the go-to guru for parents in much the same way Drs. Spock, Brazelton or Leach once were. But while Dr. Brazelton’s “Touchpoints” focused on a child’s emotional development and Dr. Leach’s “Your Baby and Child” with the minutiae of daily child rearing, Dr. Karp’s book is about a single idea: If you can sooth a crying baby, the rest will flow from there, making a parent’s job easier.

He links baby crying and parental fatigue to a host of ills, from postpartum depression, breast-feeding failure, sudden infant death syndrome, shaken baby syndrome and child abuse.

For the typically overprotective, perennially worried, “helicopter” parent, his message resonates.

“It gave me something as a father to do,” said Mr. Davenport, the early childhood education teacher in Washington, who is a big fan of the book.

“There were these five mechanical steps that you follow in a pretty particular way, and they worked. Plus the information jibed with my understanding of child development.”

Dr. Karp says his method comes as a relief to parents, who today are as project-driven as their baby boomer moms and dads were. “It’s ‘do this and this and this and you will succeed,’ ” he said in a phone interview from his Los Angeles office. “People today don’t have the support network they once had, and there’s this myth that they’re supposed to automatically know how to do it without that extended family support. Parents need to cut themselves some slack.”

Dr. Karp’s fan base is largely the professional, well-educated, middle-to- upper-middle-class demographic, but his methods are being taught by childhood educators and lactation consultants to low-income mothers who might otherwise not have the time or resources to seek out his books or other trendy tomes on child rearing.

In Pennsylvania in 2007, Dr. Karp was brought in to train 250 staffers in the Women Infants and Children program, who in turn teach their clients his methods because it increases the duration of breast-feeding. “If the infant was fussy, mothers would think they weren’t getting enough to eat,” noted Wanda Godar, a spokeswoman for the state’s Bureau of Family Health, which administers the program. “This definitely helps.”

The state’s Department of Public Welfare has also funded a pilot project in Fayette County, one of the poorest in the state, where nurses pay home visits to at-risk pregnant women and new mothers, using his DVD and a portable DVD player.

“Our babies don’t cry as much, and the parents don’t become as upset,” said Janet Debolt, director of the county’s Nurse-Family Partnership.

Dr. Todd Wolynn, a pediatrician based in Pleasant Hills and Squirrel Hill, is teaching Dr. Karp’s methods to his patients and to expectant mothers at West Penn Hospital. He’s hopeful the five “S’s” will catch on across the socioeconomic spectrum — much in the way that Dr. Spock appealed to a broad range of Americans.

“People 40 and over know Dr. Spock, and those under that age probably don’t,” Dr. Wolynn said. “Harvey has a great thing going.”

Even so, new fashions in parenting will continue to unfold, and new experts will recycle old ideas to new parents. In fact, the backlash against over parenting, touted as “news” in Time, actually began brewing back in 1990, when the term “helicopter parent” was first coined by pediatrician Foster W. Cline.

Ultimately, parents struggle to either emulate their own upbringing, or reject it, asserts Mr. Davenport.

“No matter what we read, when we get stressed, we’re going to parent the way we were parented,” he said. “We know that in our bones, because it was what we experienced.”

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• How the baby books rank, see Page A-14.

Within days of being born, babies cry in a way that reflects the language spoken by their parents.

In a study of French and German newborns, researchers with the Max Planck Society in Germany found clear differences in the tone and pitch of the babies’ cries. The French babies started low in pitch and then went higher, while the German ones did the opposite, starting high and then falling lower. According to the researchers, those modulations reflect the melody patterns typical of fluent speakers of each language.

According to Angela Friederici, one of the authors of the study, which was recently published in the journal Current Biology, babies in the last trimester of development in utero respond to noise and can sense the mother’s voice. “The sense of hearing is the first sensory system that develops,” she said, but because amniotic fluid muffles sounds, “what gets through are primarily the melodies and intonation of the respective language.”

In French, she said, a lot of words have the stress at the end, so that the intonation rises, while German is mostly the opposite. She added that “our results generalize to other languages with a clear stress pattern.