Lifespan Development Articles, Research & Resources

Karina Thadani
Last updated:
Erin L. George, MFT
Erin L. George, MFT
Medical editor

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What Is Lifespan Development? 

Lifespan development is the process in which people grow and advance through different stages of life, including infancy, childhood, and adulthood. It encompasses these areas of growth:

  • Physical: Involves physical development (such as height changes, weight changes, and puberty)
  • Cognitive: Involves mental development (such as problem-solving, knowledge, and language skills)
  • Social: Involves learning to interact with other individuals and form relationships
  • Perceptual: Involves engaging with one's environment by using senses
  • Personality: Involves developing unique traits and behaviors that make oneself distinctive
  • Emotional: Involves learning about, expressing, and managing emotions (1)

Generally, these areas mature during the aging process. However, developmental disabilities can cause delays in this growth. Common examples include attention deficit hyperactivity disorder (ADHD), autism spectrum disorder, and dyslexia. (2)

If a parent suspects their child has a developmental delay, they may find it helpful to turn to a developmental psychologist. These professionals are knowledgeable about the human maturation process and can help identify and treat developmental disabilities. (3) While these disabilities may be diagnosed at any age, they're most commonly caught in the early stages of development. (4)

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Lifespan Development Stages 

Lifespan development begins when a human is conceived and continues until the end of their life. This long process can be divided into four distinct stages:

  • Prenatal. The prenatal stage refers to the development of a fetus in the womb. (5)
  • Infancy. The infancy stage begins once a child is born and continues until they're one year in age. (6)
  • Childhood. After infancy, adults go through childhood. This covers toddler years, elementary school years, and adolescence. (7)
  • Adulthood. Adulthood begins between the ages of 18 and 21. This stage lasts for the remainder of one's life. (8)

These stages are divided based on both age and key milestones. As humans progress from one stage to the next, they experience major shifts in all forms of development. For example, people learn and express new types of emotions as they grow from infants to toddlers and young children. (9)

It's important to note that these stages can be further broken down into smaller stages of development. For instance, there are key differences between young adults and elderly individuals (even though they both fall under the "adulthood" stage). Here's a closer look at each stage.

Prenatal Development 

Also known as fetal development, the prenatal stage is the first step of development. It begins at conception and continues throughout pregnancy or until birth. The pregnancy itself can be divided into the following stages:

The first trimester begins at conception, which occurs when an egg becomes fertilized by sperm. Over time, a water-tight sac called the amniotic sac grows around the fertilized egg (or embryo) to protect it. Then, the embryo begins developing features like eyes, blood cells, and bones. After about 8 weeks of development, the embryo is referred to as a fetus. The first trimester ends once the fetus is fully formed (after about 12 weeks). At this stage, it has all its limbs and organs.

The second trimester begins at week 13 and ends at around week 28. During this period, the fetus continues to develop. Facial features become more pronounced, and certain organs and systems (such as the nervous system) become functional. The fetus will generally also exhibit movement.

The third trimester starts after the seventh month of pregnancy. Throughout this stage, the body prepares the fetus for birth. In addition to completing development, it will gain weight. Toward the end of this stage, most fetuses shift position so that the head drops into the pregnant person's pelvis. This position change indicates the fetus is ready for birth. Once it's born, it becomes a baby and officially exits the prenatal stage. (10)

Infancy Development 

The next development stage is infancy, which begins when a child is born and continues until 1 year of age. This stage is marked by major milestones in physical and cognitive development, such as the following:

  • Motor function. In the beginning of infancy, most physical development involves the head and mouth (which is used for breastfeeding). Over time, the infant may begin flexing their hands and toes. Between 6 and 9 months of age, most infants start crawling. By 12 months, infants can usually stand and walk a few steps.
  • Sensory skills. Hearing is already developed by the time a baby is born. During infancy, the child develops other senses (such as touch, taste, and smell). Their vision also expands. At about 2 months of age, infants can start tracking objects and recognizing faces. Once they hit 4 to 6 months, they can start to see colors.
  • Language skills. Newborns rely on crying to communicate their needs (such as hunger or pain). As they develop, they may start cooing or making vowel sounds. By 12 months, infants can usually imitate sounds and say preliminary words (like "mama" or "dada").

After a year, infancy concludes and the childhood stage begins. (11)

Childhood Development 

Childhood development is a long stage that starts at 1 year of age and continues until around 18 years of age. It can be broken down into the following stages:

  • Toddler (1-3 years)
  • Preschooler (3-5 years)
  • Middle Childhood (6-11 years)
  • Adolescence (11-18 years)

The toddler years come with significant developments in motor skills, language, and behavior. Many toddlers begin walking and speaking and become more self-aware. They might start copying other people's behaviors and expressing new emotions, such as defiance. (12) As they enter preschool age, children often become more independent. They might express a desire to socialize more with other children or to try new things (like riding a tricycle). (13)

Middle childhood covers the elementary school years. Throughout this period, children develop greatly in physical, cognitive, and social areas. They grow in size, learn new topics (such as reading or math), and make new friends. (14)

At around 11 years, most children start going through puberty. This causes hormonal changes that affect both physical appearance and personality. For example, many children may grow facial hair or begin menstruation. Mood swings are also common. (15) As children progress through their teenage years, they complete puberty and finish growing. Personality-wise, they usually become more independent and responsible. (16)


The final stage of lifespan development is adulthood. Like childhood, this stage can be broken down into different categories:

  • Young adulthood
  • Middle adulthood
  • Late adulthood

Young adulthood starts between 18 and 21 years of age and continues until the mid-30s. At this point, body growth is usually completed, and physical health is at its peak (unless the young adult has a health condition). Brain development, on the other hand, continues until age 25. (17) During this stage, many people continue their education, begin careers, and settle down to start families.

As humans enter middle adulthood, they start exhibiting signs of aging, such as wrinkles and graying hair. They also develop an increased risk of health problems, including heart disease and diabetes. For those who were assigned female at birth, the ability to reproduce declines. (18) In terms of life accomplishments, many people have and raise children or further their careers throughout this period.

The final stage is late adulthood, which begins in the mid-60s. As adults age, both physical and mental well-being may decline. Potential health problems include decreased immune strength, arthritis, heart disease, and Alzheimer's disease. Even with these risks, many older adults remain active and healthy. They might retire and start traveling or spend more time with family. The development cycle completes at the end of a person's life. (19)