A 1-year-old’s brain has matured enough to allow babies to recall past actions and events. As memory becomes more established, toddlers are able to learn from what they have seen other people do. For instance, a toddler may watch a person do something and then try to repeat the action later in the day or even a week later.

During early childhood development, toddlers are learning to appreciate how certain sounds, sights, smells, tastes and textures go together. Although the sense of smell is fully developed at birth, most children become aware of the difference between pleasant and foul odors around age 3.

Studies show that toddlers thrive in an environment rich in sensory stimuli. Toddlers respond to music by singing along to a song or marching and playing drums or other play instruments.

By 18 months, toddlers like to play repetitively (e.g., throwing a ball) for long periods of time. Repetition allows them to pay attention to what they are doing and learn from it. At this stage, toddlers do not require formal teaching to develop their cognitive skills. Parents or other caregivers can promote learning by listening attentively, talking often and recognizing the types of activities that interest the child.

Beginning at age 1, a baby’s babbling gradually transforms into a few simple words. A child’s first few words usually involve the name of a person, object or action. They also typically include, “hi” “bye-bye” and “no.” Most toddlers speak anywhere from 20 to 50 words by age 20 months. Around this time, a toddler's brain becomes more focused in the way it responds to language. Speech is processed more rapidly, enabling children to better understand. Toddlers can understand more language than they can express at this age.

Toddlers at this stage can point to objects or ask what they are. They enjoy simple songs, finger plays and games involving sounds and words (e.g., patty-cake). They also like practicing new words or phrases, usually before falling asleep at night or while riding in a car.

Language development varies by several factors. The number of words toddlers are able to say by their second birthday is related to many factors including gender, whether they are outgoing or shy, and whether they are part of a small or large family. Children’s surroundings may also influence their language development. For example, a child may talk more if spending more time with adults or communicate less if spending more time with other children. With older siblings, a toddler may not need to speak often if the other children talk instead. Girls are usually more advanced than boys in language abilities.

By age 2, most toddlers have an increased attention span and can often say about 300 words, including their name. They can usually point to named body parts and name pictures of items and animals. Most 2-year-olds can also form phrases of two to three words, such as “more juice” or “give me cookie.” This enables them to communicate needs, such as hunger and thirst. Many parents begin toilet training when the child is able to express a need for a diaper change or to use the toilet.

After language skills develop, toddlers incorporate it into their play. During early childhood development, a child’s play will gradually become more sophisticated, and they usually like to imitate other people by playing with play food, dolls and dress-up clothes. Most toddlers after age 2 understand that toys are symbols of things in real life.

By age 3, a child's brain is about 80 percent of adult size. Language and movement skills continue to increase dramatically, supporting a toddler's intellectual and language development. Pronunciation should also be improving steadily, and a child’s speech is generally more understandable at this time. Most 3-year-olds can compose sentences of three to five words and frequently ask questions.

Other milestones many children accomplish by age 3 include the ability to make mechanical toys work, match physical objects to pictures of the objects, sort objects by shape and color and complete puzzles with three to four pieces. Around this time, children also begin to engage in imaginary or make-believe play with dolls, animals and people. Children at this age may have imaginary friends. Make-believe play is a normal facet of early childhood development.  

By their fourth birthday, most children have a vocabulary exceeding 1,500 words. They can easily compose sentences of five to six words and are able use the past tense. Most children can say their age and sex when asked as well as correctly name some colors. Most 4-year-olds are also developing an understanding of time and are able to distinguish between two objects based on size and weight. They generally also understand the concept of counting and are able to count up to four. By age 4 or 5, memory increases further and children are able recall parts of a story. They usually also enjoy telling stories to entertain others.