In psychology the term early childhood is usually defined as the time period from birth until the age of eight years, therefore covering infancy, kindergarten and the early school years up to grades 3. There are three simultaneous development stages:
Physical growth and developmentEdit
In this phase there is significant synaptic growth and myelination of neural fibers in the brain, especially within the frontal lobes. For example, between the ages 2 and 6, the brain increases from 70% of its adult weight to 90%. The growth of the brain is followed by a surge in cognitive abilities. Around the age of five, children start speaking properly and master their hand to eye coordination.
It is optimal that an environment is provided that encourages physical development and allows the children to explore and try out new things. The physical development in children follows a pattern. The large muscles develop before the small muscles. The large muscles are used for walking, running and other physical activities. These are known as gross motor skills. Small muscles are used for fine motor skills such as picking up objects, writing, drawing, throwing and catching. 
Cognitive growth and developmentEdit
Called the preoperational stage by Jean Piaget, this is the stage during which the child repeatedly asks "Why?", and is used to build relationships with the child. The child can't yet perform the abstract thinking operations. The child has to be able to see what is being talked about, because they do not understand the concepts of logic, betrayal, contemplation, etc. This means that they think literally: if a child is told that they have to go to bed because "night is falling", they will ask how can the night (literally) fall from the sky. They also see the human characteristics in every object, e.g. the table "is bad" if they accidentally hit it with their foot and it hurts. They also exhibit egocentrism; not to be confused with egoism; that being said, they do not comprehend that the other person has beliefs and the children at this age think that what they think, everybody thinks. There is also a matter of perceptive centration, which causes the children to primarily see what is visually most prominent on someone/something, e.g. if a man has long hair, the child will think he's a woman.
Social-emotional growth and developmentEdit
This includes children understanding a sense of 'self', relationships with others and sociability. The emotional development includes expressions, attachment and personality. Children manifest fear of dark and monsters and around the age of three notice whether they are a boy or a girl and start acting that way. Boys are usually more aggressive, whilst girls are more caring. However, aggression is manifested in two different ways: boys are more physically aggressive, while the girls are more socially aggressive (name-calling and ignoring). In this stage the individual differences become more prominent.
Gross motor skillsEdit
Between ages 2 and 3 years, young children stop using the awkward, wide-legged robot-like stance that is the hallmark of new walkers. As they develop a smoother gait, they also develop the ability to run, jump, and hop. Children of this age can participate in throwing and catching games with larger balls. They can also push themselves around with their feet while sitting on a riding toy.
The period of the most rapid development of motor behaviors is between 2 and 6 years (also known as the preschool years). Skills that appear are basic locomotor, ball-handling, fine eye–hand coordination, walking leads to running, jumping, hopping, galloping, and skipping, climbing evolves from creeping.
Fine motor skillsEdit
There are several developmental expectations for children to reach by the time they reach the age of 2. Children are expected to be able to draw simple shapes such as circles, squares and triangles. The development of holding the pencil starts with a supinated grip and finishes with a "dynamic tripod" grip which involves three fingers stabilizing the utensil near the tip. They should also be able to cut out such shapes as these. By doing such activities as these develops the children's fine motor skills, by strengthening their fingers and developing their finger control.
Infants and toddlers experience life more holistically than any other age group Social, emotional, cognitive, language, and physical lessons are not learned separately by very young children. Adults who are most helpful to young children interact in ways that understand that the child is learning from the whole experience, not just that part of the experience to which the adult gives attention.
The most information learned occurs between birth and the age of three, during this time humans develop more quickly and rapidly than they would at any other point in their life. Love, affection, encouragement and mental stimulation from the parents or guardians of these young children aid in development. At this time in life, the brain is growing rapidly and it is easier for information to be absorbed; parts of the brain can nearly double in a year. During this stage, children need vital nutrients and personal interaction for their brain to grow properly. Children's brains will expand and become more developed in these early years. Although adults play a huge part in early childhood development, the most important way children develop is interaction with other children. Children develop close relationships with the children they spend a large period of time with. Close relationships with peers develop strong social connections that can be transferred later in life, even children at an early age have a preference of whom they want to interact with or form friendships with. Howes (1983) research suggested that there are distinctive characteristics of friendships, for infants, toddler and pre-school aged children.
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