Up until the two-month mark, babies are helpless and totally dependent on the mother. They can make basic distinctions between sounds, sights, noises, smells and touches. Crying, cooing, grunting and smiling begin by three months of age. At this point, babies start to lift their heads when lying on their stomachs. By the six- month mark, babies begin to babble, and are usually able to produce all the vowels and most of the consonant sounds. The six month old also recognizes familiar faces.
By ninth months, babies can sit by themselves and crawl. They are often very attached to the mother, and will cry or fuss upon separation from her. By one year, babies are often able to stand, and they have control of their legs and feet. They show affection to loved ones, and demonstrate fear of strangers. They respond to their own names, participate in "patty cake," wave goodbye to others and understand the concept of "no-no."
At this point, many toddlers are able to say between 50 and 200 words. They start to draw, are able to kick a ball and begin walking up the stairs one-by-one. They are capable of controlling their bathroom habits, so this time is suitable for toilet training. They begin to throwing temper tantrums, which will often carry on until the third year, and they show jealousy and/or resentment toward a younger sibling, if they have one.
Language skills take a major leap between the second and third year, and children begin to use short sentences. Furthermore, they begin developing emotions such as anger, sorrow and humor. They frequently copy their parents' actions and expressions, yet they also do not want to listen to their parents' requests. By the third year, children tend to become a bit bossy, and they do not like to share their toys. However, at this age, they also become more social and enjoy playing with other children.
At the age of four, children's social worlds begin to greatly expand. Often, they are enrolled in a nursery or preschool program, so they spend more time with other children than in the past. They begin to take on certain gender roles, and engage in what they see as gender-specific activities. For example, girls may play with kitchen toys and boys may play with trucks. They have more flexibility with motor skills, and are able to jump and stand on one leg.
Children are more independent by the age of five, and can generally dress and undress themselves. They begin writing letters, and can draw more detailed pictures. Thousands of words are in their vocabulary, and they frequently tell lengthy tales. Their social lives are key, and friendships are very important to them. They begin to feel new emotions, such as pride in their accomplishments, and responsibility and guilt in their wrongdoings.