Some of what a newborn does comes from reflexes, which are movements a baby makes without choosing to. Doctors check a newborn's reflexes to see whether the brain and nervous system are working well. When a newborn's palm is stroked, the baby's fingers close around the finger. That is the grasp reflex, and it lasts until a baby is about 5 to 6 months old. A baby's toes curl when the sole of the foot is touched. That is a grasp reflex in the feet, and it lasts until about 9 to 12 months.

When a baby's cheek is touched, the baby turns toward the touch and opens their mouth. This is the rooting reflex, and it helps the baby find food. Babies also have a hand-to-mouth reflex that goes with rooting and sucking, so they may suck on their fingers or hands. Babies bring their hands to their mouths and put things in their mouths to explore. The rooting reflex fades within the first several months, at about 4 to 6 months.

A loud sound or a sudden move can make a baby stretch out their arms and legs and then pull them back in. This is the startle reflex, and a baby's own cry can set it off. Babies can hear loud sounds from the start. Newborns begin to recognize important sounds around them, such as the voice of a caregiver. A familiar, gentle voice can calm a crying baby.

Babies cry to tell the people near them what they need, such as food, a hug, a clean diaper or sleep. A baby's first signs of communication come when the baby learns that a cry brings food, comfort and company. Babies cry more in their first 3 months than at any other time, and crying usually gets better after that. Babies also begin to smile back at people who talk and smile to them, usually within the first few months. Around 4 months many smile on their own to get a grown-up's attention and chuckle. Around 6 months they laugh.

At birth, babies cannot see as well as older children or adults, because their eyes and visual system are not fully developed. A newborn's eyes focus best on things about 8 to 12 inches (20 to 30 centimeters) away, about as far as a parent's face. Newborns like to look at faces. They also like black-and-white patterns with strong contrast. By eight weeks, babies begin to focus more easily on the faces of the people near them.

In 1980, researchers showed that newborns would change how they sucked to switch on a recording of their mother reading a nursery rhyme. Babies learn the sounds of the language around them. By 6 months most recognize its basic sounds. As babies grow they begin to sort out the speech sounds that make up the words of their language. Studies using artificial languages suggest that infants use statistical information in the speech stream to find where words begin and end.

In the first few months, up to about 4 months, babies coo, making soft pleasure sounds like oooo and aahh. Babbling comes next, strings of sounds like tata, upup and bibibi, and it starts in the first year of life. Around 6 months many babies take turns making sounds with a grown-up. Serve and return is a back-and-forth between a baby and a caring grown-up, like a game of tennis. A baby coos or babbles, the adult answers, and the baby learns.

Newborns sleep a lot, and most are asleep more than they are awake. As of November 2026, a common guide is 14 to 17 hours, and anywhere from about 8 to 18 hours can be normal. Newborns do not have a sense of day and night yet, and they wake often to eat because their stomachs are tiny. As babies grow they can sleep longer at night. By around 6 months some sleep for up to 12 hours, but every baby has a different sleep pattern.

As of November 2026, Singapore's Health Promotion Board says a baby's brain roughly doubles in weight in the first year. In the first few years of life the brain grows new connections at a very fast rate. The brain is built from the bottom up, with simple connections and skills developing first, followed by more complex circuits and skills. After a period of especially rapid growth in the first few years, the brain refines itself through pruning, which makes its circuits more efficient. The early years are the most active time for making neural connections, but new connections can form throughout life.

Words to know

• reflex: automatic movement
• pruning: trimming extras
• contrast: strong difference
• babbling: strings of sounds