Human Development During the First Two Years After Birth


The first two years after birth are considered to be the most important ones from the perspective of the development of an individual. This period is critical due to the rapid growth of an infant and the evolution of the brain. The time is characterized by numerous milestones, which prove the correct development of a child from the perspectives of biosocial, cognitive, and psychological development. It is generally thought that environmental factors play the most significant roles in these processes and have a crucial impact on the future individuality of a person.

Biosocial Development during the First Two Years after Birth

Physical Development of a Child

In the first few days after birth, children typically lose several ounces. The growth is the most rapid during the first year of life. By the age of 4 months, the weight of healthy newborns doubles and, by a year, it triples (Berger, 2017). To compare the development of infants, there is a concept of percentile, which is “a point on a ranking scale of 0 to 100. The 50th percentile is the midpoint; half the people in the population being studied rank higher and half rank lower” (Berger, 2017, p. 284). In case, the result is higher or lower than norms, the infant should be consulted by a pediatrician. Little gain of weight can be a sign of poor nutrition, allergies, or other medical conditions, while obesity can be caused by overfeeding or genetic problems.

Newborn babies spend most of the time sleeping and it decreases as they grow. Little children spend the most time in REM (rapid eye movement) sleep, a stage “characterized by flickering eyes behind closed lids, dreaming, and rapid brain waves” (Berger, 2017, p. 285). When an infant is 3 or 4 months, they experience an increase in quiet sleep, also called slow-wave sleep (Berger, 2017). However, the patterns may vary due to genetic inclination or environmental factors, including the type of nutrition and parental behaviors.

There are also numerous debates about co-sleeping or sharing a bed with parents. For example, in the United States, the number of families practicing it doubled from 1993 to 2010, from 6.5 to 13.5 percent (Berger, 2017). Mothers often choose this way to react to the baby’s needs more quickly. However, experts are concerned with it as it doubles the chances of Sudden infant death syndrome (SIDS). Another important factor is that the patterns for future behaviors are established during the first two years, so in case children share a bed with their parents, they may continue coming there for many years.

Brain Development of a Child

During the first two years after birth, the brain of a child grows more rapidly than other organs. It demonstrates approximately 25 percent of adult weight at birth and reaches 75 percent in two years (Berger, 2017). The prenatal and postnatal development of the brain defines the later cognitive functions of a person. Nature has also thought about the mechanism of protecting this crucial organ with the help of head-sparing, guaranteeing that the brain has more time before it would begin to suffer from malnutrition, disrupting body growth (Berger, 2017). The brain of an individual at birth is characterized by the existence of extra neurons, which disappear as the result of the evolution, while others develop.

These complicated processes are happening during the first years of infants’ lives and the brain undergoes continuous formation while the child receives various experiences when communicating with other people or touching different objects. The brain of a human being cannot develop when there is a lack of opportunities for learning and exploration.

Skills Development

To develop motor skills during the first year, infants use their senses. After the child is born, they have all of them functioning: their eyes see, ears hear, noses can smell, tongues and skin are responsive. However, eyesight is not developed as newborns can focus only on things between 4 and 30 inches away but it is quickly developing, allowing a child to see faces clearly by the age of 2 months (Berger, 2017). The use of the senses leads to the development of motor skills as the first two years are the ones when the child learns to crawl, sit, and walk.

The norms for these experiences may also vary, but crawling and sitting usually begin at 6 months, while walking is expected at approximately one year. It is important to remember that in case one aspect of the system of senses and motor skills lags, it may influence other parts as well. Slow development of one of the elements may signal the problem, demanding a consultation with a specialist.

Cognitive Development during the First Two Years after Birth

Cognitive Development

Infant cognition is composed of early reflexes, senses, and body movements. A Swiss psychologist Jean Piaget, known for proving that during the first two years, babies learn actively, called it sensorimotor intelligence (Berger, 2017). There are several stages of cognitive development of infants: primary, secondary, and tertiary circular reactions (Berger, 2017). The primary type is divided into the stage, which lasts from birth to 1 month and is characterized by sucking and grasping, and the second stage, which lasts till 4 months, implies coordination of reflexes. Secondary circular reactions describe the child’s responses to objects and people.

There are also two stages: the first (from 4 to 8 months) is characterized by the baby reacting to the actions they like and the second (lasting to 12 months) implies becoming more purposeful in reacting to others and achieving the desired results. The third milestone is the most creative actions and ideas. The first stage here lasts from 12 to 18 months and involves exploration of the world, while the second stage, which lasts till the baby is two years, implies thinking before doing.

Information Processing

Understanding the cognition of infants is difficult as they cannot put their thoughts into words. Many researchers use the concept of the workings of a computer, including input, memory, programs, analysis, and output to receive an idea about the ways the human brain uses various experiences for cognition development (Berger, 2017). Studies have shown that information processing is advancing as the child grows.

For example, the cry is a reflex for a newborn and it requires no cognition, while later the child learns to use it to signal their needs, such as hunger. There are two specific aspects of infant cognition, affordances, implying perception or input, and memory, concerning brain organization or output (Berger, 2017). Affordance is an opportunity for interaction, which is offered by all objects and people, which becomes a stimulus for the baby to process new information. Memory is a tool, available to infants since birth, which is proven by the fact that children learn to recognize the voices and faces of their parents. The opportunities for information processing are increasing as the child grows and lead to their future development, including the acquisition of speech.

The Language Development

The ability of a person to use their native language at the age of two is surprising. According to specialists, “infants are acquiring much of their native language before they utter their first word” (Berger, 2017, p. 352). Babies listen to adults speaking and figure out the patterns, necessary for producing speech. Numerous studies have also shown that children of bilingual parents learn to distinguish between the languages in their early childhood (Berger, 2017).

It is corresponding with the theory of Piaget, who claimed that babies can think as the work of the brain enables people to communicate. The language skills of an infant are developing rapidly and when they are one year old, they are typically capable of understanding simple phrases and often begin to say their first words. The baby learns three or more names every day and by the age of two, most children can form sentences consisting of several words. Experts have been studying the processes in the brain, attempting to explain the quick development of the language, which led to the appearance of various theories, based on behaviorism, sociocultural concept, and evolutionary psychology.

The first one is represented by psychologist Skinner and implies a necessity to teach children as, according to his view, parents serve as tutors to their babies and help them with numerous repetitions of the same patterns (Berger, 2017). The second theory is called social-pragmatic, explaining that children learn to communicate due to the social nature of human beings (Berger, 2017). The last school, treating language acquisition from the perspective of evolutionary psychology, states that “it arises from the universal genetic impulse to imitate” (Berger, 2017, p. 366). This theory explains that it is also a reason why some children are more talkative than others at the same age.

The hypothesis became a basis for future research and later Noam Chomsky offered a conception that humans are born with a specific mental structure, responsible for learning a language, which is called a language acquisition device (LAD) (Berger, 2017). This system allows brains to develop and learn the grammar of the native language. However, none of the theories is proven to provide answers to all the questions about language development and there is a probability that it derives from a combination of all these ideas.

Psychological Development during the First Two Years after Birth

Emotional Development and the Importance of a Positive Environment

The emotional development of infants is complex as it moves from basic instincts to learned and, then, thought reactions. Newborns feel happy and relaxed when they are dry and fed. As they grow, they develop more emotions, such as smiling and laughing at the age of 3 or 4 months, anger at 4-8 months, and fear of unexpected happenings after the age of one year. The studies have also proved that abuse and negative emotions, such as sadness, “produce physiological stress (measured by cortisol levels)” and have a serious impact on infants (Berger, 2017, 377). Such an environment affects the brain and contributes to children becoming fearful and depressed.

As opposed to negativity, positive emotions help to increase the social awareness of infants, developing empathy and generosity. Infancy is also a time of the development of social bonds and the feeling of attachment to their parents. According to numerous types of research, the relationships with mothers and fathers define the future of the person, allowing them to grow successful and self-confident in case the environment in the family is favorable.

Theories of Infant Psychological Development

The fact that children are social and emotional beings led to the development of multiple theories of their psychological evolution. One of the conceptions is behaviorism, implying that infants learn from other people and copy their reactions and emotions (Berger, 2017). Another approach is cognitive, stating that thoughts determine the perspectives of a person, who develop working models, a set of assumptions used to organize perceptions and experiences, for different situations (Berger, 2017). However, one of the most popular theories was offered by Sigmund Freud and Erik Erikson and united biosocial and psychosocial development (Berger, 2017).

According to this concept, Freud distinguished two stages, oral and anal (Berger, 2017). The first one defines the first year of life as children exploring the world through the mouth, while the second is characterized by the satisfaction of bowel movements, which allows controlling them. Erikson highlighted two crises: trust versus mistrust, when “infants learn whether or not the world can be trusted to satisfy basic needs” and autonomy versus shame and doubt, which occurs with the emergence of self-awareness (Berger, 2017, p. 407). Both Freud and Erikson believed that the experiences during the first two years define the future individuality of the person.


The first two years after birth are the most significant ones, regarding the development of an individual from the perspectives of biosocial, cognitive, and psychological development. This is the period, which is characterized by the most rapid physical growth, brain advancement, and emotional evolution. During the first two years of life, an infant acquires all the basic skills, including the ability to walk, speak, and interact with other people. Multiple studies have proved that the experiences of a child at this age have a crucial impact on their future life, individuality, and problems.


Berger, K. S. (2017). The developing person through the life span (10th ed.). Worth Publishers.

Create a citation

Choose a citation style


StudyStroll. (2022, July 17). Human Development During the First Two Years After Birth.

Work Cited

"Human Development During the First Two Years After Birth." StudyStroll, 17 July 2022,

1. StudyStroll. "Human Development During the First Two Years After Birth." July 17, 2022.


StudyStroll. "Human Development During the First Two Years After Birth." July 17, 2022.


StudyStroll. 2022. "Human Development During the First Two Years After Birth." July 17, 2022.


StudyStroll. (2022) 'Human Development During the First Two Years After Birth'. 17 July.

Click to copy

A student like you wrote this sample on Human Development During the First Two Years After Birth. You may use this work for educational purposes. A correct citation is necessary if you want a fragment from the sample to be present in your paper.

Request for Removal

Send a removal request if you created this work and want it removed from the StudyStroll database.