When it comes to sleep, we’re typically told that, age by age, kids require a specific number of hours per day (12 to 14 hours for toddlers, for instance). But a recent study suggests that sleep needs in individual children can vary widely. Researchers at University Children’s Hospital Zurich in Switzerland tracked the sleep patterns of more than 300 children and found that there was a large range in the number of hours they slept. They also observed that kids who needed less sleep remained that way throughout their childhoods. “It’s not appropriate to say that a three-year-old should sleep twelve and a half hours a day when our research found that sleep duration at this age ranged between ten and a half and fourteen and a half hours—a difference of four hours,” says Oskar G. Jenni, MD, the study’s lead author. In short, putting a child who naturally needs less sleep to bed too early can actually lead to problems such as trouble falling asleep. To tell how much shut-eye your child needs, keep track of her behavior rather than the number of hours she sleeps, suggests Dr. Jenni. If she dozes off in front of the TV or within minutes of getting in the car or is cranky during the day, she may need more zzz’s. If you create a soothing nightly ritual (no TV, gradual winding down, quiet reading) and she still has difficulty falling asleep at bedtime, she may need a schedule tailored to her natural need for less sleep.