Despite reams of research papers and dozens of books on the subject, the age-old question of how to get a baby to sleep still draws a huge variety of answers, from letting a baby cry until he falls asleep to never letting him cry.

Even the American Academy of Pediatrics, which recently released a book, “Guide to Your Child’s Sleep: Birth Through Adolescence,” falls short of endorsing one method, instead offering pros and cons to the most popular theories.

“Sleep is the power source for the brain,” says Dr. Mark Weissbluth, a Chicago pediatrician and author of the newly revised “Healthy Sleep Habits; Happy Child,” (Ballantine, $14.95). “It allows the child to perform better and have a better mood.”

While Weissbluth is referred to by some as the father of the “Cry it out” method, there is actually much more to his theory than that. A father of four and a leading researcher on sleep in children, he hinges his advice on a simple notion: Prevent sleep problems from happening — starting the day you bring your baby home from the hospital — rather than trying to fix them later.

His research suggests that children have natural, age-specific sleep rhythms largely dictated by the development of specific portions of the brain.

The parent’s job, he says, is to look for subtle cues of drowsiness which occur at certain times in every child and, “respect the child’s need to sleep at those times, providing a quiet place for them to do that.”

Newborns are biologically programmed to need massive amounts of sleep and have trouble tolerating more than one or two hours of wakefulness at a time, he says. After they are past six weeks of age, their tiny brains start to dictate a need to go to bed much earlier, so parents should adjust their schedules accordingly, he says.

At 12 to 16 weeks, he says, a portion of the baby’s forebrain begins to hunger for a regular morning nap.

Again, it is up to the parents to accommodate them, he says.

“There is this belief out there that some children just don’t need to sleep very much, but I see it as an excuse used by some parents to ignore their children’s need to sleep,” he says.

In those babies who are very difficult to put down, it is wise to let them cry until they fall asleep — a method referred to as the “extinction,” or “cry it out,” for a few nights, he says.

While he acknowledges it sounds harsh, he believes it works faster than other methods to get a baby into a good sleep pattern and will prevent sleep problems from developing down the line.

For those who can’t stand the idea of letting their baby cry for hours, pediatric sleep expert Richard Ferber offered a different solution in his landmark 1986 book, “Solve Your Child’s Sleep Problems.” Ferber recommends creating a bedtime ritual, such as a bath, then putting the child to bed awake. Then, he writes, parents should let the child cry and visit periodically, at progressively longer intervals, to check on the baby, but not touch her.

The American Academy of Pediatrics sees this as a good way for the baby to learn he is “in his crib to stay,” and more comfortable for parents who may not be able to handle the “Cry it out,” method. But, the AAP points out, scheduled visits may get the baby’s hopes up and provoke further crying.

On the other end of the spectrum from the Ferber method is the Family Bed, an increasingly common practice advocated author and pediatrician Dr. Williams Sears in the 1993 bestseller, “The Baby Book.”

Proponents say sharing a bed brings the family closer, makes breast feeding easier and makes for more restful sleep because it eliminates middle-of-the night runs to the crib.

But critics, including the AAP, say it may unnecessarily prolong night feedings, keep parents and children from sleeping well, may make it hard for a child to adapt to his own bed; and may be dangerous for a baby.