infancy

Infancy is the earliest stage of human development, spanning birth through the first year of life. It is characterized by rapid physical growth, brain development, and the emergence of foundational cognitive, language, and social skills. The World Health Organization defines infancy as ages birth to 12 months.

During this period, growth proceeds quickly. Birth weight typically doubles by about 4 to 6 months and triples by the end of the first year. Growth is supported by nutrition, most commonly exclusive breastfeeding or formula in the first six months, followed by the introduction of age-appropriate complementary foods while continuing milk feeding.

Motor development follows a relatively predictable sequence but varies among individuals. Newborns show reflexes such as rooting and sucking; by 2–4 months they lift the head, by about 6 months they may roll and sit with support, and by 9–12 months they may stand or walk with assistance.

Cognitive and sensory development includes rapid gains in perception, attention, and memory. Object permanence generally becomes evident between 8 and 12 months. Babies explore with hands and mouth, imitate actions, and learn through repetitive experiences.

Language and social development emerge in tandem. Vocalizations progress from cooing to babbling, with first words typically emerging near or after 12 months. Social interactions, emotional bonding, and early communication with caregivers lay the foundation for later learning. Sleep patterns become more regular but remain variable.

Healthcare considerations include growth monitoring, immunizations, safe sleep practices, and screening for developmental concerns. Variations exist across cultures and individual circumstances, but responsive caregiving supports healthy infancy.