At age 4 to 5, children who still take afternoon naps will give them up, and parents (or teachers) will learn to get by without that precious hour or two for themselves.

Most 4- and 5-year-olds still need a regular time every afternoon for quiet play, “reading” and rest. Most will also need about 12 hours of sleep every night. But these are also the years for new nighttime disturbances.

All children this age are likely to become louder and more assertive — and recognize that their behavior can get a rise out of you. As a child becomes aware of her own aggressive feelings, she may feel overwhelmed. When she gets away with breaking the rules, it is even more frightening. Discipline is reassuring at this age because it says, “Someone knows where the boundaries are.”

Along with this urgent need to test limits come experiences that let her see whether she can get away with magical wishes. My 4-year-old granddaughter will say, “I’m in love with you. You’re my Bapa and I want to marry you.”

“I’m already married to your grandmother.”

“Well, that won’t matter. You have just got to do what I tell you. I’m in charge.”

If she heard herself, it could be pretty frightening.

These wishes and feelings can be handled during the day but not at night. Suddenly a grandmother witch begins to invade her bedroom. A monster hides in the closet. Loud noises such as barking dogs and sirens take on a new meaning.

The child’s own threats and retaliations come back to haunt her. She senses that having these thoughts — or imaginary powers — is close to being out of control.

Behind the thoughts is her new awareness of her limitations: “I’m so little that I have to stomp my feet and yell.” But she scares herself when she tries to feel powerful. She is bound to worry that the witches and monsters at night are her punishment.

Children who begin to want to feel in charge are prone to nightmares as a balance to this surge in aggressive feelings.

Here is how to ease night fears:

• Emphasize the bedtime ritual all over again. Read to her. To help the transition, warn her: “This is the last book we’re going to read. I know it’s hard to stop. But when it’s over, that’s the time for a lullaby and kiss goodnight. Then — lights out.”

• Don’t hesitate to cuddle with her, but with a limit.

• Look under the bed and in the closet. “Witches are scary, even though we both know they’re not real.”

• Comfort her when she awakens and repeat the above routine.

• Finish up the nighttime comforting with a firm ending and the expectation that she can handle it.

• Encourage her to rely on her doll or blanket or stuffed toy.

• During the day, respect her aggressive outbursts. Let her blow off steam. Afterward, you can even say, “That’s really scary, isn’t it? I get upset too when I feel angry.” But make sure you set the limits she needs. After she’s lashed out at someone, comfort her and say, “You know I can’t let you do that. It’s scary, isn’t it?”

• Maintain discipline, which becomes more important than ever: “I must stop you until you can stop yourself.” Knowing this will give your child peace of mind not just during the day, but alone in bed at night.

(This article is adapted from “Sleep: The Brazelton Way” by Dr. T. Berry Brazelton and Dr. Joshua Sparrow. It is published by Da Capo Press, a member of The Perseus Books Group.)

Questions or comments should be addressed to Dr. T. Berry Brazelton and Dr. Joshua Sparrow, care of The New York Times Syndicate, 620 Eighth Ave., 5th Floor, New York, N.Y. 10018. Questions may also be sent by e-mail to:

nytsyn-families@nytimes.com