Growth and Development, Ages 2 to 5 Years

	Topic Overview
	Health Tools
	What to Expect
	Common Concerns
	Promoting Healthy Growth and Development
	When to Call a Doctor
	Routine Checkups
	Other Places To Get Help
	Related Information
	References
	Credits

How does a child grow and develop between the ages of 2 and 5?

The ages between 2 and 5 are often called the preschool years. During these years, children change from clumsy toddlers into lively explorers of their world. A child develops in these main areas:

• Physical development. In these years, a child becomes stronger and starts to look longer and leaner. Physical growth is slower than in the first 2 years of life, but the outward changes can be dramatic.
• Cognitive development. A child this age makes great strides in being able to think and reason. In these years, children learn their letters, counting, and colors. Their play becomes more creative as they learn to imagine.
• Emotional and social development. Between the ages of 2 and 5, children gradually learn how to manage their feelings. They begin to feel ashamed or guilty when they do something wrong. By age 5, friends become important.
• Language. The ability to use words grows quickly in these years. By age 2, most children can say at least 50 words. By age 5, a child may know thousands of words and be able to carry on conversations and tell stories.
• Sensory and motor development. By age 2, most children can walk up stairs one at a time, kick a ball, and draw simple strokes with a pencil. By age 5, most can dress and undress themselves; draw a person with a head, body, arms, and legs; and write some small and capital letters.

Children usually move from one important point (or milestone) in their development to the next in a natural pattern. For example, most children say single words before they speak in sentences. But each child grows and gains skills at his or her own pace. It is common for a child to be ahead in one area, such as language, but a little behind in another.

Learning what is normal for children this age can help you spot problems early or feel better about how your child is doing.

When are routine medical visits needed?

Between the ages of 2 and 5, a child usually goes to the doctor at age 24 months and 30 months and then once a year at ages 3, 4, and 5 years. These routine checkups are called well-child visits. These visits are important to check for problems and to make sure that your child is growing and developing as expected.

During these visits, the doctor will do a physical exam and give your child any needed shots. The doctor will weigh and measure your child to see how your child compares to other children of the same age. The doctor will also ask questions about your child's behavior and your family. He or she may also ask your child questions about favorite activities or friends.

Well-child visits are a good time to talk to your doctor about any concerns you have with your child's health, growth, or behavior. Between visits, write down any questions you want to ask the doctor next time.

When should you call a doctor?

Call your doctor anytime you have a concern about your child's physical or emotional health. Be sure to call if your child:

• Is not reaching developmental milestones as expected.
• Is not growing at a steady pace.
• Has lost skills he or she used to have, such as talking or running.
• Is violent or abusive.
• Doesn't seem to be doing well, even though you can't pinpoint what makes you uneasy.

How can you help your child during these years?

It’s important to learn about some of the behaviors you can expect during these years of rapid change. Temper tantrums, thumb-sucking, and nightmares are common issues in children this age. Knowing what to expect can help you to be patient and get through the stressful moments.

The best thing you can do for your child is to show your love and affection. But there are also many other ways you can help your preschooler grow and learn:

• Offer your child healthy foods. Keep lots of fruits, vegetables, and healthy snacks in the house.
• Make time for your child to be active. Limit TV viewing to no more than 1 or 2 hours a day.
• Read and talk to your child. This helps children learn language and opens them up to new ideas.
• Help your child get enough rest. Between the ages of 2 and 5, children need about 11 to 13 hours of sleep each day.
• Give your child a chance to meet and play with other children. Preschool or play groups can be a great way for children to learn to interact.
• Teach skills, such as how to get dressed or use the toilet. Watch for signs that your child is ready, and try to move ahead at his or her pace.
• Set limits that help your child feel safe and secure but that also allow the child to explore.

Raising a preschooler can be challenging. What works or is right for a 2-year-old may not be right for a 5-year-old. Taking a parenting class can help you learn how to deal with issues as they arise. To find a parenting class, ask your child’s doctor or call a local hospital.

Frequently Asked Questions

Health tools help you make wise health decisions or take action to improve your health.

	Actionsets are designed to help people take an active role in managing a health condition.
	Helping your child develop healthy self-esteem
	Interactive tools are designed to help people determine health risks, ideal weight, target heart rate, and more.
	Interactive Tool: What Is Your Child's BMI?

General development between ages 2 and 5 years

Children between the ages of 2 and 5 change dramatically in five major areas: emotional and social skills, physical growth, thinking and reasoning skills (called cognitive development), language development, and sensory and motor development. Children usually progress in a natural, predictable sequence from one developmental milestone to the next. But the exact timing varies from child to child. Also, many children tend to make progress in one area, such as learning new words, while another skill, such as counting, levels off.

• Emotional and social development begins with excitement about being around other children at age 2. But most children at this age play near each other rather than with each other (this is called parallel play). By age 5, most children seek and enjoy friendships. Often they identify a playmate as their "best friend," although their choice may change frequently. Two-year-olds start to recognize the differences between boys and girls. By age 5, children understand many of these differences and often like to dress or play in ways they identify with their gender.
• Physical development slows down from the rapid growth during infancy. From age 2 through age 5, most children annually gain about 3 lb (1.4 kg) to 5 lb (2.3 kg) and grow about 3 in. (7.6 cm).
• Cognitive development, or thinking and reasoning skills, progresses from a simple to more complex understanding of time, letters, counting, and colors. Children are able to follow increasingly more detailed commands. Play gradually becomes more inventive and richly imaginative.
• Language develops rapidly between ages 2 and 5. By age 2, children usually can say at least 50 words. They can recognize the names of many objects and some body parts (such as arms and legs). By age 3, children are learning new words quickly. Most can speak between 150 and 200 words and can follow two-part directions, such as "Wash your face and put your shoes away." They also start to use plurals and short complete sentences that most of the time are understood by others outside of their family. Four-year-olds use longer sentences and can describe an event. Most 5-year-olds can carry on a conversation.
• Sensory and motor skills become more refined, from being able to walk up stairs, kick a ball, and draw simple strokes to basic tumbling and drawing rough figures of people and other recognizable objects. Children also gradually learn to dress themselves and handle their toilet needs independently.

Milestones by age

By 2 years of age, your child:

• Grows at a steady pace, although it has slowed from the phase of rapid growth during the first 18 months of life.
• Alternates between feeling excited, confused, and scared about his or her emerging independence. Temper tantrums may start occurring regularly.
• Says at least 50 words and uses 2-word sentences.
• Runs and can go up and down stairs.

By 3 years of age, your child:

• Looks leaner and longer compared to the early toddler years. Most children have gained about 4.4 lb (2 kg) and grown about 3 in. (8 cm) since their second birthday.
• Plays pretend, understands 3-step instructions, enjoys simple puzzles, and knows his or her name, age, and sex.
• Enjoys playmates, although "sharing" is often still a challenge.
• Separates from you easily.
• Is interested in or has completed toilet training.
• Uses 4- to 5-word sentences, including some pronouns and plurals.
• Jumps, runs, climbs, pedals a tricycle, and kicks a ball. He or she will likely be able to screw and unscrew lids, draw simple strokes, use silverware, build a tower with at least 6 blocks, and turn pages one at a time.

By 4 years of age, your child:

• Has gained about 4.4 lb (2 kg) and grown about 3 in. (8 cm) since turning 3.
• Can say his or her name, identify some basic colors, and match things that are the same (such as a pair of socks).
• Can tell the difference between fantasy and reality. But a 4-year-old's active imagination can create all kinds of scary and threatening scenarios.
• Has mastered most grammar skills. He or she speaks in sentences with at least 5 or 6 words, tells stories, and sings songs.
• Hops on one foot, rides a tricycle (or a small bike with training wheels), throws a ball overhand, and goes up and down stairs without holding onto anything. He or she can use safety scissors, draw circles and squares, and write some capital letters.

By 5 years of age, your child:

• Has gained about 4.4 lb (2 kg) and grown about 3 in. (8 cm) since turning 4.
• Knows his or her address and phone number, most letters of the alphabet, how to count up to 10, and basic concepts of time.
• Acts independently much of the time and understands rules.
• Likes to please others and have friends. But it is normal for children this age to sometimes act unkindly. Five-year-olds are still learning about understanding and being sensitive to other people's feelings.
• Carries on conversations and uses more advanced grammar, such as the future tense.
• Hops on one foot, somersaults, and possibly skips. Most 5-year-olds can dress and undress themselves; draw a person with a head, body, arms, and legs; and write some small and capital letters from the alphabet.

Common problems parents encounter with their children during the preschool years relate to sleep, eating, safety, and difficult emotions and behavior.

Sleeping

Preschool children between the ages of 2 and 5 need about 11 to 13 hours of sleep each day. Your preschooler may go through phases when he or she resists resting. Sometimes children may refuse to go to sleep as a way to assert their independence. Other times, they may simply need extra attention or reassurance before they feel safe and comfortable enough to sleep well.

You can help foster good sleep habits by:

• Setting bedtime routines. Do things in the same order each night so that the child understands what to expect and associates these steps with going to sleep.
• Handling sleep disturbances in a consistent manner. Sometimes young children wake up and want attention or reassurance. Keep your response the same each time your child wakes up. Sleep problems often become worse if the child is rewarded with attention. Many times, children quickly fall back asleep on their own. If you feel you need to go into your child's room, make the visit quick and businesslike.
• Helping prevent nightmares. Preschool-age children's rich fantasy lives and active imaginations make them prone to nightmares. These typically occur toward the end of the night or very early morning. You can help prevent nightmares by controlling what you allow your child to watch on television. In addition, encouraging your child to regularly talk about daily events helps a child understand his or her environment. This prevents a child from feeling confused or fearful, which also can lead to nightmares.
• Managing night terrors. Night terrors are different from nightmares because the child remains asleep throughout the entire episode and does not have any memory of it in the morning. Night terrors tend to occur about 3 to 5 hours after the child goes to sleep; nightmares usually happen at the end of the night. Children cry intensely and often lose their breath, which often frightens parents. After 10 to 30 minutes, the child will settle down and return to a deep sleep. Do not try to wake a child during a night terror. Instead, reassure your child and hold him or her to prevent injury. Do not be alarmed if your child seems unaware of your presence. Most children grow out of this sleep behavior. Making sure your child gets enough sleep can help reduce the frequency of night terrors.

Eating

Finicky eating habits are common and normal in preschoolers. Many children have smaller appetites than they had in their younger years because they are growing more slowly. As long as you offer nourishing foods from the major food groups and focus on the big picture—how much is eaten throughout the entire day or over the course of a few days—your child should not have problems. With a parent's guidance, a child naturally balances out his or her diet in an average week.

Safety

To keep a child safe, a parent or caregiver must always be aware of the child's abilities and the environment, whether it is the home, a playground, or a public place. These abilities change as the child grows and gains new skills.

For more information on safety issues, see the topic Health and Safety, Ages 2 to 5.

Behavior

Children between ages 2 and 5 have many intense emotions that they do not fully understand. As a result, expect your young child to not always listen to you. If you exercise patience and do your best to be consistent about limits you set, you can avoid some common preschool behavior issues, which include:

• Temper tantrums. These emotional outbursts are perhaps the biggest behavior challenge for this age group. Many 2- to 4-year-olds have temper tantrums at least once a week. A tantrum is a normal and expected response when something or someone interferes with a young child's attempt to achieve independence or to master a skill. For example, a tantrum may occur when the child becomes angry because he or she does not want to go to bed. For more information, including guidance on how to respond to tantrums, see the topic Temper Tantrums.
• Thumb-sucking. Thumb-sucking in children younger than 4 years old is not usually a problem. Most children stop sucking their thumbs on their own sometime between ages 3 and 6 years. They usually do not need treatment. But children who suck their thumbs frequently or with a lot of force after the age of 3 or 4 may develop emotional, dental, or speech problems. For more information, see the topic Thumb-Sucking.
• Breath-holding spells. These are periods of time when young children stop breathing, frequently causing them to pass out (lose consciousness). Breath-holding spells typically happen when a young child is angry, frustrated, in pain, or afraid. But the spell is a reflex, not a deliberate behavior on the child's part. Breath-holding spells usually occur in children between the ages of 6 months and 4 years, though spells can begin as early as 2 months of age. Some children continue to have spells until they are as old as 6 or 7. Making sure your child gets plenty of rest and helping your child to feel secure and less frustrated may help reduce the number of these episodes. For more information, see the topic Breath-Holding Spells.
• Aggression. Some preschool children become aggressive and may hurt other children physically or emotionally. Hitting, biting, pushing, and shouting are all common forms of aggression. Children's aggressive behavior usually is a normal variation of their temperament. Children gradually learn to control their aggressive feelings as they begin to recognize the feelings of others. Parents can encourage aggressive children to learn self-control by teaching positive behavior and how to channel their feelings into words or other nonphysical expression. Do not spank or hit your child—it usually is ineffective and only instills fear. First, help your child calm down. Later, you can talk about better ways to respond to their feelings. Do not expect immediate changes in behavior. Time, repetition, and reinforcement are usually needed for the lessons to stick. For more information on topics related to aggression, see the topics Biting or Bullying.

Toilet training

A child must be both physically and emotionally ready to use the toilet. Otherwise, efforts are usually unsuccessful and frustrating for both the parent and the child. Although there is great variation between individual children, most are ready for toilet training when they are between 24 and 36 months of age.

You may be confused about when to initiate toilet training. This is not surprising, considering most people are bombarded with advice and expectations from relatives, friends, and day care providers. You may also have personal reasons for wanting your child toilet trained, such as being pregnant and wanting to avoid having two children in diapers at the same time. But your child's physical and emotional readiness for toilet training is the most important aspect of the timing. Although you can begin toilet training your child at an earlier-than-average age, it usually takes longer. Also, both you and your child will likely become frustrated if you attempt toilet training before he or she is physically and emotionally ready.

For more information, see the topic Toilet Training.

As a parent, you can enhance your preschool child's development in countless ways, the most important of which is showing love and affection. You guide your children through the challenges of this important time of life by talking and reading to them, providing opportunities for play, playing pretend with them, showing them how to get dressed or use the toilet, and setting boundaries and limits to their behavior.

You can also try specific techniques to help your child advance in all areas of growth and development.

Promote physical development by:

• Offering plenty of opportunities for exercise. Going to the playground, joining a gymnastics or dance class, or simply running races in your backyard allows your child to release excess energy and encourages new physical skills.
• Helping your preschooler develop healthy eating habits. Although you control what, when, and where your child eats, realize that he or she chooses whether to eat and how much. As long as you offer nourishing foods from the major food groups and focus on the big picture—how much is eaten throughout the entire day or over the course of a few days—your child should not have problems. Use the family meal as an opportunity to promote healthy eating habits, both by your example of good eating behavior and how you respond to your child's shifting food preferences.

Promote cognitive development by:

• Encouraging safe exploration. Exploration helps your child discover cause-and-effect relationships. Children who explore learn to master new skills and solve problems. Offer a variety of things to play with, read, create, and build. Resist limiting exploration because of safety fears by taking basic measures to minimize risks. For more information about preventing accidents and injuries, see the topic Health and Safety, Ages 2 to 5 Years.
• Encouraging a sense of security. Your child is more likely to feel safe and secure if you are dependable, consistent, respectful, and responsive. These qualities are especially important for parents of preschool children, because these children are gaining a basic sense of trust in themselves and in the significant people in their lives. This sense of trust lays the foundation for learning, social skills, adaptability, and emotional development. Secure children also keep and strengthen their attachment to their parents.

Promote emotional and social development by:

• Providing peer contact. Playing with other children even 1 day a week gives children opportunities to practice and develop important social, emotional, and language skills. Children learn to share, cooperate, and negotiate as they interact with their peers.
• Promoting self-control. Children need guidance, clear limits, and patient parents during this time of behavioral and emotional struggles. Help your child by modeling and teaching proper behavior. Also, encourage your child to think about the feelings of other people to develop empathy. Preschoolers crave acceptance and attention. Completely ignoring a misbehaving child is effective in curbing minor but annoying behavior problems, such as whining or complaining. Time-outs can also help, when they are used properly and sparingly.
• Helping your child develop healthy self-esteem. The foundation of self-esteem is established in childhood. Parents have the greatest influence on a child's belief about himself or herself. Letting your child know that he or she belongs, is doing well, and is contributing can help him or her develop healthy self-esteem.

Promote language development by:

• Reading to your child at every age. Reading exposes your child to the sounds and rhythm of language. It also helps stimulate the imagination and introduces children to things and places they may not have a chance to learn about otherwise, such as oceans or dinosaurs.
• Providing opportunities to talk with others. Children develop language skills by being around other people. Listening and communicating with other children and adults helps a child to understand and use language.

Promote sensory and motor development by:

• Providing a wide variety of experiences and play environments. Schedule time each day for either indoor or outdoor physical activity, such as dancing inside or going to a playground. These types of activities improve coordination and other large muscle skills. Fine motor skills develop through art projects (such as painting or using scissors), playing musical instruments, pouring, and using tongs or fingers to move objects. Stimulate your child's senses by introducing new sights, smells, sounds, textures, and tastes as often as you can.

Your relationship with your child will constantly change as your child gains new skills and develops independence. You can help your child through each stage of development by evaluating your relationship from time to time. In many ways, you have to "get to know" your child over and over again. Ask yourself:

• What do I like most about my child?
• What could be triggering bad behavior? Are any of these new triggers?
• What new skills has my child developed within the past 3 months? 2 months? 1 month?
• What tasks can I encourage my child to do for himself or herself? How can I encourage him or her?
• When am I happy about how I treat my child?
• What don't I like about some of our interactions? When do these episodes tend to occur?

As a parent or caregiver of children, it is also important for you to:

• Learn and use effective parenting and discipline techniques and avoid the use of corporal punishment. Parenting classes are offered in most communities. Ask your health professional or call a local hospital for more information.
• Learn healthy techniques to resolve conflicts and manage stress. For more information, see the topic Stress Management.
• Ask for help when you need it. Call a family member or friend to give you a break if you feel overwhelmed. Investigate community resources that are available to help you with child care or other necessary services. Call a health professional or local hospital for a place to start. Some communities have respite care facilities for children, which provide temporary child care during times when you need a break.

Although your child grows at an individual pace, be aware of signs of a developmental delay. The earlier you identify a delay, the better chance you have of getting appropriate treatment for your child that can prevent or minimize long-term problems.

In general, talk to a doctor anytime your child:

• Does not seem to be reaching developmental milestones as expected.
• Is not growing at a steady pace. Each year between ages 2 and 5 years, expect your child to gain about 3 lb (1.4 kg) to 5 lb (2.3 kg) and grow about 3 in. (7.6 cm). Although your child's height and weight are measured at routine well-child exams, call your doctor if your child's growth pattern concerns you in between these visits.
• Is not able to do some of the things he or she used to do, such as talking or running.
• Makes you so angry or frustrated with your child that you are worried about what you might do next.
• Acts overly aggressive, violent, or verbally abusive.
• Does not seem to be doing well, even though you can't pinpoint what makes you uneasy. Friends and other caregivers may also be concerned.

Call your doctor if by age 2 your child:¹

• Walks on his or her toes frequently and does not use a normal heel-toe pattern most of the time.
• Does not speak or use 2-word sentences.
• Does not imitate actions of others.
• Is not able to follow simple instructions.

Call your doctor if by age 3 your child:²

• Falls frequently while trying to walk or is not able to go up and down stairs.
• Drools frequently, does not speak clearly, and can't talk in 2- or 3-word sentences.
• Does not make regular eye contact.
• Can't build a tower of more than 4 blocks, move small objects, or copy a circle.
• Does not play "pretend" or like to play with toys and other children.
• Has problems separating from you.

Call your doctor if by age 4 your child:²

• Does not know how to throw a ball overhand, jump in place, or ride a tricycle.
• Can't hold a crayon between the thumb and fingers.
• Responds only to family members and does not enjoy being around other children.
• Does not use sentences with more than 3 words or use pronouns correctly.
• Shows no interest in playing "pretend."
• Has frequent temper tantrums.
• Is not toilet trained.
• Regularly resists getting dressed in the morning or going to sleep at night.

Call your doctor if by age 5 your child:²

• Goes from one activity to another without being able to focus on one thing for at least 5 minutes.
• Does not like to play "pretend" or try new activities.
• Regularly resists using the toilet, sleeping, or eating.
• Speaks unclearly or can't use plurals or other basic parts of speech.
• Has trouble building a tower out of blocks, holding a crayon, getting dressed, brushing teeth, or washing hands. These are all tasks related to motor skill development.
• Often behaves in ways that seem unusual. For example, he or she may seem:
  • Afraid, unable to separate from you easily, overly quiet, or unhappy.
  • To have little or no emotion.
  • Not to enjoy playing with other children or people other than close family members.

Between the ages of 2 and 5, a child usually see the doctor at age 24 months and 30 months and then once a year at ages 3, 4, and 5 years. These routine checkups are called well-child visits. These appointments allow your child's doctor to keep a close eye on your child's general health and development. Finding out possible problems early gives your child the best chance for proper and successful treatment. In addition, any concerns you have about your child can be discussed during these visits.

Physical examination

To evaluate a child's general health and whether physical developmental milestones are being met, a doctor generally will:

• Measure your child's weight and height. These measurements are plotted on a growth chart to see how your child compares physically to other children of the same age. This chart is updated each year during the routine exam to document the child's growth pattern. You can check your child's body mass index (BMI) at home to estimate whether your child is at a healthy weight for his or her height, age, and sex. To find out your child's BMI, use this Interactive Tool: Is Your Child at a Healthy Weight?
• Check your child's blood pressure.
• Examine your child for any visible problems.
• Review your child's immunization record. Needed immunizations are given or scheduled. For more information, see the topic Immunizations or the childhood immunization record(What is a PDF document?).
• Ask you about your child's eating and sleeping habits.

Mental and emotional health evaluation

The doctor will talk with both you and your child to get a sense of his or her mental, emotional, and social development. Questions generally cover:

• Whether any noticeable behavioral changes have occurred.
• Your child's and family's general well-being. The doctor also observes how you and your child interact.
• How your child reacts to strangers.
• How your child plays and interacts with peers.
• Whether you have any concerns about issues such as toilet training, preschool, or troubling behaviors.
• Your child's language, hearing, and social skills. The doctor directly asks your child questions to briefly assess these and related developmental issues. For example, the doctor may ask your child about his or her favorite activities and the names of his or her friends.

In addition to the above assessments, health professionals usually ask questions specific to a child's age.

Most children will have formal hearing tests during the 4-year and 5-year routine exams. Vision tests usually occur at ages 3, 4, and 5. Your child may have formal testing at a younger age if there are concerns about any area of the child's development.

Routine checkups are a good time for you to ask about development and discuss your concerns about your child's health, growth, development, or behavior. It may help you to go to your child's checkup with a prepared list of questions(What is a PDF document?).

Online Resources

Organizations

• Basic Dental Care
• Bed-Wetting
• Biting
• Breath-Holding Spells
• Choosing Child Care
• Cuts
• Early Disease Detection
• Environmental Illness
• Head Injury, Age 3 and Younger
• Health and Safety, Ages 2 to 5 Years
• Healthy Eating for Children
• Immunizations
• Lead Poisoning
• Objects in the Ear
• Playground Safety
• Poisoning
• Preventing Poisoning in Young Children
• Scrapes
• Speech and Language Development
• Temper Tantrums
• Thumb-Sucking
• Toilet Training
• Urinary Problems and Injuries, Age 11 and Younger

Citations

1. American Academy of Pediatrics (2004). Age two to three years. In SP Shelov, RE Hannemann, eds., Caring For Your Baby And Young Child: Birth to Age 5, 4th ed., chap. 11, pp. 301–338. New York: Bantam.

2. American Academy of Pediatrics (2004). Age three to five years. In SP Shelov, RE Hannemann, eds., Caring For Your Baby And Young Child: Birth to Age 5, 4th ed., chap 12, pp. 339–388. New York: Bantam.

Other Works Consulted

• Committee on Psychosocial Aspects of Child and Family Health, American Academy of Pediatrics (1998). Guidance for effective discipline. Pediatrics, 101(4): 723–728.

• Dixon SD, Stein MT (2006). Encounters With Children: Pediatric Behavior and Development, 4th ed. Philadelphia: Mosby Elsevier.

• Goldson E, Reynolds A (2007). Child development and behavior. In WW Hay et al., eds., Current Pediatric Diagnosis and Treatment, 18th ed., pp. 66–101. New York: Lange Medical Books/McGraw-Hill.

• Green M, Palfrey JS, eds. (2002). Bright Futures: Guidelines for Health Supervision of Infants, Children, and Adolescents, 2nd ed. Arlington, VA: National Center for Education in Maternal Health.

• Lucas BL (2004). Nutrition in childhood. In LK Mahan, S Escott-Stump, eds., Krause's Food, Nutrition, and Diet Therapy, 11th ed., pp. 259–283. Philadelphia: Saunders.

• Needlman RD (2004). Preschool years. In RE Behrman et al., eds., Nelson Textbook of Pediatrics, 17th ed., pp. 44–50. Philadelphia: Saunders.

• Strasburger VC (2005). Television. In S Parker et al., eds., Developmental and Behavioral Pediatrics: A Handbook for Primary Care, 2nd ed., pp. 425–427. Philadelphia: Lippincott Williams and Wilkins.