Children begin to lose their baby fat, or chubbiness, around age 3. Toddlers soon acquire the leaner, more athletic look associated with childhood. The child's trunk and limbs grow longer, and the abdominal muscles form, tightening the appearance of the stomach. Even at this early stage of life, boys tend to have more muscle mass than girls. The preschoolers' physical proportions also continue to change, with their heads still being disproportionately large, but less so than in toddlerhood.
Three‐year‐old preschoolers may grow to be about 38 inches tall and weigh about 32 pounds. For the next 3 years, healthy preschoolers grow an additional 2 to 3 inches and gain from 4 to 6 pounds per year. By age 6, children reach a height of about 46 inches and weigh about 46 pounds. Of course, these figures are averages and differ from child to child, depending on socioeconomic status, nourishment, health, and heredity factors.
Brain and nervous system developments during early childhood also continue to be dramatic. The better developed the brain and nervous systems are, the more complex behavioral and cognitive abilities children are capable of.
The brain is comprised of two halves, the right and left cerebral hemispheres. Lateralization refers to the localization of assorted functions, competencies, and skills in either or both hemispheres. Specifically, language, writing, logic, and mathematical skills seem to be located in the left hemisphere, while creativity, fantasy, artistic, and musical skills seem to be located in the right hemisphere. Although the hemispheres may have separate functions, these brain masses almost always coordinate their functions and work together.
The two cerebral hemispheres develop at different rates, with the left hemisphere developing more fully in early childhood (ages 2 to 6), and the right hemisphere developing more fully in middle childhood (ages 7 to 11). The left hemisphere predominates earlier and longer, which may explain why children acquire language so early and quickly.
Another aspect of brain development is handedness, or preference for using one hand over the other. Handedness appears to be strongly established by middle childhood. About 90 percent of the general population is right‐handed, while the rest of the population is left‐handed and/or ambidextrous. A person is ambidextrous if he or she shows no preference for one hand over the other. Typically, right‐handedness is associated with left‐cerebral dominance and left‐handedness with right‐cerebral dominance.
The nervous system undergoes changes in early childhood, too. The majority of a child's neurons, or cells that make up nerves, form prenatally. However, the glial cells, (nervous system support cells surrounding neurons) that nourish, insulate, and remove waste from the neurons without actually transmitting information themselves, develop most rapidly during infancy, toddlerhood, and early childhood. The myelin sheaths that surround, insulate, and increase the efficiency of neurons (by speeding up the action potential along the axon) also form rapidly during the first few years of life. The postnatal developments of glial cells and myelin sheaths help to explain why older children may perform behaviors that younger children are not capable of.
Motor skills are physical abilities or capacities. Gross motor skills, which include running, jumping, hopping, turning, skipping, throwing, balancing, and dancing, involve the use of large bodily movements. Fine motor skills, which include drawing, writing, and tying shoelaces, involve the use of small bodily movements. Both gross and fine motor skills develop and are refined during early childhood; however, fine motor skills develop more slowly in preschoolers. If you compare the running abilities of a 2‐year‐old and a 6‐year‐old, for example, you may notice the limited running skills of the 2‐year‐old. But the differences are even more striking when comparing a 2‐year‐old and 6‐year‐old who are tying shoelaces. The 2‐year‐old has difficulty grasping the concept before ever attempting or completing the task.
Albert Bandura's theory of observational learning is applicable to preschoolers' learning gross and fine motor skills. Bandura states that once children are biologically capable of learning certain behaviors, children must do the following in order to develop new skills: