(See also Learning and Developmental Disorders.)

Development is often divided into specific domains, such as gross motor, fine motor, language, cognition, and social/emotional growth. These designations are useful, but substantial overlap exists. Studies have established average ages at which specific milestones are reached, as well as ranges of normality. In a normal child, progress within the different domains varies, as in the toddler who walks late but speaks in sentences early (see Table 2: Physical Growth and Development: Developmental Milestones*).

Table 2
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Developmental Milestones* Age Behavior Birth Sleeps much of the time Sucks Clears airway Responds with crying to discomforts and intrusions 4 wk Brings hands toward eyes and mouth Moves head from side to side when lying on stomach Follows an object moved in an arc about 15 cm above face to the midline Responds to a noise in some way (eg, startling, crying, quieting) May turn toward familiar sounds and voices 6 wk Regards objects in the line of vision Begins to smile when spoken to Lies flat on abdomen Head lags when pulled to a sitting position 3 mo Holds head steady on sitting Raises head 45° when lying on stomach Opens and shuts hands Pushes down when feet are placed on a flat surface Swings at and reaches for dangling toys Follows an object moved in an arc above face from one side to the other Watches faces intently Smiles at sound of caretaker's voice Vocalizes sounds 5–6 mo Holds head steady when upright Sits with support Rolls over, usually from stomach to back Supports self in a standing position Reaches for objects Recognizes people at a distance Listens intently to human voices Smiles spontaneously Squeals in delight Babbles to toys 7 mo Sits without support Bears some weight on legs when held upright Transfers objects from hand to hand Holds own bottle Looks for dropped object Responds to own name Responds to being told “no” Combines vowels and consonants to babble Moves body with excitement in anticipation of playing Plays peek-a-boo 9 mo Sits well Crawls or creeps on hands and knees Pulls self up to standing position Works to get a toy that is out of reach; objects if toy is taken away Gets into a sitting position from stomach Stands holding on to someone or something Says “mama” or “dada” appropriately in reference to parents Plays pat-a-cake Waves bye-bye 12 mo Walks by holding furniture (“cruising”) or hands May walk 1 or 2 steps without support Stands for a few moments at a time Drinks from a cup Speaks several words Helps dress self 18 mo Walks well Can climb stairs holding on Turns several book pages at a time Speaks about 10 words Pulls toys on strings Partially feeds self 2 yr Runs well Climbs up and down stairs alone Turns single book pages Puts on simple clothing Makes 2- or 3-word sentences Verbalizes toilet needs 3 yr Rides a tricycle Dresses well except for buttons and laces Counts to 10 and uses plurals Recognizes at least 3 colors Questions constantly Feeds self well Can take care of toilet needs (in about half of children) 4 yr Alternates feet going up and down stairs Throws a ball overhand Hops on one foot Copies a cross Washes hands and face 5 yr Skips Catches a bounced ball Copies a triangle Knows 4 colors Dresses and undresses without help *The sequence is fairly consistent, but the timing of milestones varies; times above represent median values. Developmental Milestones* Age Behavior Birth Sleeps much of the time Sucks Clears airway Responds with crying to discomforts and intrusions 4 wk Brings hands toward eyes and mouth Moves head from side to side when lying on stomach Follows an object moved in an arc about 15 cm above face to the midline Responds to a noise in some way (eg, startling, crying, quieting) May turn toward familiar sounds and voices 6 wk Regards objects in the line of vision Begins to smile when spoken to Lies flat on abdomen Head lags when pulled to a sitting position 3 mo Holds head steady on sitting Raises head 45° when lying on stomach Opens and shuts hands Pushes down when feet are placed on a flat surface Swings at and reaches for dangling toys Follows an object moved in an arc above face from one side to the other Watches faces intently Smiles at sound of caretaker's voice Vocalizes sounds 5–6 mo Holds head steady when upright Sits with support Rolls over, usually from stomach to back Supports self in a standing position Reaches for objects Recognizes people at a distance Listens intently to human voices Smiles spontaneously Squeals in delight Babbles to toys 7 mo Sits without support Bears some weight on legs when held upright Transfers objects from hand to hand Holds own bottle Looks for dropped object Responds to own name Responds to being told “no” Combines vowels and consonants to babble Moves body with excitement in anticipation of playing Plays peek-a-boo 9 mo Sits well Crawls or creeps on hands and knees Pulls self up to standing position Works to get a toy that is out of reach; objects if toy is taken away Gets into a sitting position from stomach Stands holding on to someone or something Says “mama” or “dada” appropriately in reference to parents Plays pat-a-cake Waves bye-bye 12 mo Walks by holding furniture (“cruising”) or hands May walk 1 or 2 steps without support Stands for a few moments at a time Drinks from a cup Speaks several words Helps dress self 18 mo Walks well Can climb stairs holding on Turns several book pages at a time Speaks about 10 words Pulls toys on strings Partially feeds self 2 yr Runs well Climbs up and down stairs alone Turns single book pages Puts on simple clothing Makes 2- or 3-word sentences Verbalizes toilet needs 3 yr Rides a tricycle Dresses well except for buttons and laces Counts to 10 and uses plurals Recognizes at least 3 colors Questions constantly Feeds self well Can take care of toilet needs (in about half of children) 4 yr Alternates feet going up and down stairs Throws a ball overhand Hops on one foot Copies a cross Washes hands and face 5 yr Skips Catches a bounced ball Copies a triangle Knows 4 colors Dresses and undresses without help *The sequence is fairly consistent, but the timing of milestones varies; times above represent median values.

Environmental influences, ranging from nutrition to stimulation and from the impact of disease to the effects of psychologic factors, interact with genetic factors to determine the pace and pattern of development.

Assessment of development occurs constantly as parents, school personnel, and clinicians evaluate children. Many tools are available for monitoring development more specifically. The Denver Developmental Screening Test facilitates evaluation in several domains. The scoring sheet indicates the average ages for achieving certain milestones and nicely shows the critical concept of a range of normality. Other tools can also be used (see Table 2: Physical Growth and Development: Developmental Milestones*).

Motor development: Motor development includes fine motor (eg, picking up small objects, drawing) and gross motor (eg, walking, climbing stairs) skills. It is a continuous process that depends on familial patterns, environmental factors (eg, when activity is limited by prolonged illness), and specific disorders (eg, cerebral palsy, intellectual disability, muscular dystrophy). Children typically begin to walk at 12 mo, can climb stairs at 21 mo, and run well at 2 yr, but the age at which these milestones are achieved by normal children varies widely. Motor development cannot be significantly accelerated by applying increased stimulation.

Language development: The ability to understand language precedes the ability to speak; children with few words usually can understand a great deal. Although delays in expressive speech are typically not accompanied by other developmental delays, all children with excessive language delays should be evaluated for the presence of other delays in development. Children who have delays in both receptive and expressive speech more often have additional developmental problems. Evaluation of any delay should start with an assessment of hearing. Most children who experience speech delay have normal intelligence. In contrast, children with accelerated speech development are often of above-average intelligence.

Speech progresses from the utterance of vowel sounds (cooing) to the introduction of syllables that start with consonants (ba-ba-ba). Most children can say “Dada” and “Mama” specifically by 12 mo, use several words by 18 mo, and combine words into some sentences by 2 yr. The average 3-yr-old can carry on a conversation. These milestones are highly variable.

Cognitive and social/emotional development: Cognitive and social/emotional development refers to the intellectual and psychologic maturation of children as their physical development allows them to interact more with other people and the external world. There are multiple theories of these forms of development in children and adolescents; the oldest and most famous are those proposed by Freud, Piaget, and Erikson. All are based on clinical observations, but none has been tested in large groups of children. In general, these models are considered useful for describing aspects of development in some children, but none is universally applicable. Increasingly, appropriate attachments and nurturing in infancy and early childhood are recognized as critical factors in cognitive growth and emotional health. For example, reading to children from an early age, providing intellectually stimulating experiences, and providing warm and nurturing relationships all have a major impact on growth in these domains. Intellect is appraised in young children by observations of language skills, curiosity, and problem-solving abilities. As children become more verbal, intellectual functioning becomes easier to assess using a number of specialized clinical tools. Once children start school, they undergo constant monitoring as part of the academic process.

Emotional growth and the acquisition of social skills are assessed by watching children interact with others in everyday situations. When children acquire speech, the understanding of their emotional state becomes much more accurate. As with intellect, emotional functioning can be delineated more precisely with specialized tools.

Last full review/revision September 2009 by Daniel A. Doyle, MD

Content last modified September 2009