Infants (birth to age 1) are the youngest human beings. They are born into the world with tiny bodies and minds that are growing and developing at an amazing rate. Even though they cannot yet talk or walk, infants are capable of feeling a wide range of emotions, exploring their surroundings, and forming attachments to the people who care for them.
During the first year of life, infants grow rapidly both physically and cognitively. They learn to control their bodies, explore their environments, and begin to understand the people and things around them. Although each infant is unique, there are some common milestones that most babies reach during this time.
At birth, an infant’s head is about one-quarter of its adult size but grows quickly so that by age 1 it is about three-quarters the size of an adult’s head. The brain also grows rapidly during infancy, more than tripling in size by age 1. This growth enables infants to develop their motor skills—the ability to control their body movements—and startle reflex—the automatic response to sudden noises or movement nearby.
During the first few months of life, infants gain control over their bodies through practice and exploration. For example, they learn to hold up their heads, sit without support, roll over from stomach to back, and eventually stand and take steps with help. As they become more mobile, they also begin to develop a sense of object permanence—the understanding that objects continue to exist even when they cannot be seen or heard. This milestone allows infants to play simple games such as peek-a-boo because they know that even though they can’t see mom or dad’s face when it is hidden behind a blanket, mom or dad still exists.
From birth onwards,…