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(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* ).
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Table 2
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| Developmental Milestones* |
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Age
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Behavior
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Birth
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Sleeps much of the time
Sucks
Clears airway
Responds with crying to discomforts and intrusions
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4 wk
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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
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6 wk
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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
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3 mo
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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
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5–6 mo
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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
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7 mo
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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
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9 mo
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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
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12 mo
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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
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18 mo
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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
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2 yr
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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
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3 yr
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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)
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4 yr
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Alternates feet going up and down stairs
Throws a ball overhand
Hops on one foot
Copies a cross
Washes hands and face
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5 yr
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Skips
Catches a bounced ball
Copies a triangle
Knows 4 colors
Dresses and undresses without help
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*The sequence is fairly consistent, but the timing of milestones varies; times above represent median values.
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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
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