Population differencesEdit. Individual differencesEdit. Individual differencesEdit

Population differences in growth are largely related to adult stature. Ethnic groups that are quite tall in adulthood are also longer at birth and throughout childhood, as compared to groups that have short adult stature. Males are also somewhat taller, although this is more apparent in ethnic groups with strong sexual dimorphism in adulthood. Populations that are characteristically malnourished are also shorter throughout life. However, there are few population differences in growth rates or patterns, except that poor environmental conditions may delay puberty and the associated growth spurt. The markedly different age at puberty of boys and girls means that boys and girls of age 11 or 12 are at very different points in maturation and may reverse the usual sex difference in physical size.

Individual differencesEdit

Individual differences in height and weight during childhood are considerable. Some of these differences are due to family genetic factors, others to environmental factors, but at some points in development they may be strongly influenced by individual differences in reproductive maturation.

Motor developmentEdit

What develops?Edit

A child while learning to walk

Abilities for physical movement change through childhood from the largely reflexive (unlearned, involuntary) movement patterns of the young infant to the highly skilled voluntary movements characteristic of later childhood and adolescence. (Of course, older children and adolescents retain some reflex movements in addition to developing voluntary movement.)

Speed and pattern of developmentEdit

The speed of motor development is rapid in early life, as many of the reflexes of the newborn alter or disappear within the first year, and slows later. Like physical growth, motor development shows predictable patterns of cephalocaudal (head to foot) and proximodistal (torso to extremities) development, with movements at the head end and in the more central areas coming under control before those of the lower part of the body or the hands and feet. Types of movement develop in stage-like sequences; for example, locomotion at 6–8 months involves creeping on all fours, then proceeds to pulling to stand, "cruising" while holding on to an object, walking while holding an adult's hand, and finally walking independently. Older children continue the sequence by walking sideways or backward, galloping, hopping, skipping with one foot and walking with the other, and finally skipping. By middle childhood and adolescence, new motor skills are acquired by instruction or observation rather than in a predictable sequence.

Mechanisms of motor developmentEdit

The mechanisms involved in motor development involve some genetic components that determine the physical size of body parts at a given age, as well as aspects of muscle and bone strength. Nutrition and exercise also determine strength and therefore the ease and accuracy with which a body part can be moved. Opportunities to carry out movements help establish the abilities to flex (move toward the trunk) and extend body parts, both capacities being needed for good motor ability. Skilled voluntary movements develop as a result of practice and learning.

Individual differencesEdit

Normal individual in motor ability are common and depend in part on the child's weight and build. However, after the infant period, normal individual differences are strongly affected by opportunities to practice, observe, and be instructed on specific movements. Atypical motor development may be an indication of developmental delays or problems such as autism or cerebral palsy.

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