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Infancy and Childhood

Discusses milestones that occur during infancy and the first few years of childhood.

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Does a baby learn much during his first year?

The first years of life are full of important milestones as new skills are mastered. For example, at first this baby wasn't even able to roll over on his stomach or hold up his head!

Infancy and Childhood

The first year after birth is called infancy. Infancy is a period when the baby grows very fast. During infancy, the baby doubles in length and triples in weight. Other important changes also happen during infancy:

  • The baby's teeth start to come in, usually at about six months of age (Figure below).
  • The baby starts smiling, paying attention to other people, and grabbing toys.
  • The baby begins making babbling sounds. By the end of the first year, the baby is starting to say a few words, such as “Mama” and “Dada.”
  • The baby learns to sit, crawl, and stand. By the end of the first year, the baby may be starting to walk.

This baby is six months old, and his baby teeth have started to come in. Babies often chew on toys or other objects when they are getting new teeth. They may even chew on their toes.

Childhood begins after the baby’s first birthday and continues until the teen years. Between one and three years of age, a child is called a toddler. During the toddler stage, growth is still fast, but not as fast as it was during infancy. A toddler learns many new words. The child even starts putting together words in simple sentences. Motor skills also develop quickly during this stage. By age three, most children can run and climb steps. They can hold crayons and scribble with them. They can also feed themselves and use the toilet.

From age three until the teens, growth is slower. The body also changes shape. The arms and legs get longer compared to the trunk. Children continue to develop new motor skills. For example, many young children learn how to ride a tricycle and then a bicycle. Most also learn how to play games and sports (Figure below). By age six, children start losing their baby teeth. Their permanent teeth begin coming in to replace them. They also start school and learn how to read and write. They develop friendships and become less dependent on their parents.

Children develop better motor skills as they get older.


  • childhood: Phase of life that begins after the first year and continues until the teen years.
  • infancy: First year of life after birth in humans.
  • toddler: Child aged one to three years.


  • The first year after birth is called infancy, after which childhood begins.
  • An individual grows quickly and develops new abilities during infancy and childhood.


Use the resource below to answer the questions that follow.

  1. At what age do the researchers like to see infants to study cognitive development?
  2. Why is it important to establish a baseline in research of this nature?
  3. How do researchers hope to use information they are collecting to help children with language problems?


  1. What changes happen during infancy?
  2. At what stage does a developing human grow the fastest?

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