Ask the experts: Solo napping

My 8-month-old baby typically goes to sleep just fine on his own at night, but won’t take a nap without me rocking him or rubbing his back until he falls asleep. I know he can go to sleep on his own—why won’t he do it during the daytime?
A: Usually, a baby who is able to fall asleep on his own during the night also does it for day naps. However, when some infants (like your son) don’t, the first thing is to look at is whether the timing of your baby’s sleep patterns is in order. If the amount of time passing between waking up and being put to bed is consistent but you’re still having problems getting him to nap during the day, several factors may be at play.
Many families find it easier to have strict routines in the evening than during the day, as in the daytime there are more distractions and interruptions. This means the child gets less clear messages about falling asleep on his own for naptime. For example, if you are resolved to let your son fall asleep on his own during the day, but one day you rock him a little bit (because he was crying, for example), he may want to do it again two days later. Unconsciously, you may start to rock him nearly every day, and consequently it becomes a habit.
We also tend to hold our babies more during the day, and they will fall asleep in our arms every now and then, especially in the beginning. When children love falling asleep in our arms they can, little by little, start demanding to be held to help them fall asleep. Bear in mind that it is important for the baby’s neurobiological development to cuddle and hold him in our arms or simply to be with him. But it’s also important for us to learn how to establish rules as parents.
How can you break these habits and teach your baby to fall asleep on their own, even during the day? The easiest way is to change the baby’s environment. A baby’s habitual behavior is triggered by cues from the adult or the situation, so we have to change the cues. You’ll want to establish a new and consistent routine for where the baby sleeps (during the day), how he is put to sleep, who does it and what is done before his put down for his naps.
—Arna Skula, clinical nurse specialist at the Chidlren’s Hospital in  Reykjavik, Iceland, and author of Sweet Dreams: How to Establish and Maintain Good Sleep Habits for Your Baby