From the moment your child wakes up totally refreshed in the morning, the benefits of his sleep time are used up as the hours pass, and an urge to return to bed begins to build. Catching your little one during in-between stages and helping him nap builds up his reservoir of sleep-related benefits, allowing him a “fresh start” after each bout of rest.

As kids age, the length of time that they can stay “happily awake” increases. A newborn can only be awake one or two hours before tiredness sets in, whereas a two year old can last five to seven hours before craving some down time for a nap. When children are pushed beyond their biological awake time span without a break, they become fatigued, fussy and unhappy. Check our chart to see how long your baby should stay awake between catching zzz’s:

  • Newborns: one to two hours between naps
  • 6 months: two to three hours between naps
  • 12 months: three to four hours between naps
  • 18 months: four to six hours between naps
  • 2 year old: five to seven hours between naps
  • 3 year old: six to eight hours between naps
  • 4 year old: six to twelve hours between naps

As the day progresses, and the sleep pressure builds, your tiny tot becomes fussier, with more crying spells, more tantrums, and less patience. He loses concentration and the ability to learn and retain new information. Scientists refer to this process as “homeostatic sleep pressure” or “homeostatic sleep drive”—informally dubbed The Volcano Effect.

Throughout the day, your baby’s biology demands a sleep break to regroup, refresh and repair. Without this break, the problem intensifies: the rumblings and tremors become an outright explosion. The homeostatic pressure continues building until the end of the day, growing in intensity—like a volcano—and your happy-go-lucky kid is suddenly overtired, wired and inconsolably cranky, often resulting in a bedtime battle. Try these tricks for getting your child to nap peacefully:

  • Spot sleepiness signals. Yawning, rubbing eyes, and a disinterest in play all point to your baby’s fatigue. As soon as you see these signs, he’s probably due for a lie-down.
  • Stay still. Fight the urge to let your little one nap in his car seat as you run errands. Sure, he’s napping, but resting on-the-go can build up his homeostatic pressure—and leave him cranky.
  • Create a cocoon. Soft music, dim lighting and soothing sounds will help your baby get comfortable enough to doze off. Make his sleep atmosphere as relaxing as possible to discourage cat-naps instead of full-blown sleep.

Even more, if your little one skips naps day after day, he’ll build a sleep deprivation that launches him into the volcano stage much easier and quicker. If he’s missing naps and also lacking the right quality or quantity of nighttime sleep…watch out!

If you have a newborn or a young baby on your hands, you already know that these tiny tots have a much shorter span in which their sleep pressure builds. Your baby rapidly reaches the peak of his volcano in one to three hours—which is why newborns snooze throughout the day, and why young babies require two or three or four daily naps. Over time, as his sleep cycle matures, he’ll be able to go longer stretches of time between sleeps. By age 4 or 5, your child will be able to go happily through the entire day without a nap.

Caring for kids on top of the daily grind often leaves parents begging for a nap—and sleep research from the National Sleep Foundation suggests that there’s a scientific explanation for feeling bone-tired. Even in adulthood, a mid-day nap or rest break of 20-30 minutes is extremely beneficial in reducing the sleep pressure, and improving mood, alertness and performance.

The Volcano Effect isn’t only turning your kid into a tiny tyrant—the biological process affects you as well. Understanding this can help you interpret what’s really going on at the end of a long day, when kids are whiny and parents grumpy—turning your home into a veritable Ring of Fire.

Also, issues such as the previous poor night’s sleep, on-going sleep deprivation, or daily stress exacerbate the Volcano Effect. What's more, each person’s moodiness feeds off the others, causing contagious crankiness. As your child stomps around, you’ll find yourself losing patience and saying things like, “I’m sorry, honey. Mommy’s just tired right now”—a very telling explanation that’s often not analyzed.

Quality naps can make up for lost night sleep, but extra zzz’s at night doesn’t make up for missed naps, due to the homeostatic sleep pressure concept. No matter how hectic your day gets, avoid the urge to skip your baby’s daytime sleep—it’s crucial to make time for daily naps and give your kid the chance to release the rising sleep pressure.

Parenting educator Elizabeth Pantley is the president of Better Beginnings, Inc., a family resource and education company. She is also the author of twelve parenting books, including the popular "No-Cry" series.