Question: We have a two-year-old who was always a good sleeper but seems to be manipulating us now. He is a good napper and sleeps from noon-3 p.m. each day but not always the same amount. We have the same nightly routine — bath, books, bed — but the past few months, he has been crying the minute we put him in his crib and leave the room. We come back and reassure him, but his crying and our reassurance can go on for an hour.

I don't know whether this is pure manipulation. He goes into bed at 8 p.m. and often doesn't fall asleep until between 8.30 p.m. and 9 p.m. If he doesn't nap, we put him in bed earlier than 8 p.m. Once he's asleep, he sleeps through the night. It's the routine of getting him to fall asleep that worries me. We have not had sleep issues with him in the past. Do you have some advice for us?

Answer: Though most toddlers and pre-schoolers rather would stay up and play with their parents than go to sleep at bedtime, your son is unlikely to be consciously manipulating you. But that doesn't mean he isn't playing some games with you. Consider that some children need less sleep and shorter naps than others. Most parents are glad to have some respite in the afternoon while their children sleep, so I hardly can blame you for letting your son sleep for as long as he'd like. Because the problem at bedtime has only appeared recently, it's likely that he's had too much sleep in the afternoon. Alternatively, you could choose to put him to sleep a little later, when he may be more tired. However, if you like the 8 p.m. bedtime, awake him gently at 1:30 p.m. for a few days in a row to determine whether that helps him welcome bedtime more easily.

Toddlers often go through sleep problems they've not experienced before and could be having some new fears. He also could have become more sensitive to sounds or shadows in the room. Temporarily adding a night light or quiet music can reassure him. Though it's all right for you to go in once to reassure him, continued reassurances for an hour could become an all-too-comfortable habit for your son.

Reducing his naptime and discontinuing your reappearances will work to get him sleeping on his own again. If he cries too desperately, wait at least 15 minutes before you go in to reassure him, and then gradually extend the time between reassurances until he learns to fall asleep on his own again. In case you think that changing sleeping patterns are unusual, let me assure you that this happens multiple times for children as they grow and become more sensitive to their environments. I'm hoping that your son's annoying new habit is gone by the time you receive this answer, but I'm certain that there are other parents who will appreciate advice for this common problem.

Dr. Sylvia B. Rimm is the director of the Family Achievement Clinic in Cleveland, Ohio, a clinical professor of psychiatry and pediatrics at the Case Western Reserve University School of Medicine, and the author of many books on parenting.