Learning Targets:

Outline the stages of prenatal development and discuss the impact of teratogens on this process.
Identify some of the capabilities of newborns and describe how researchers investigate infants' cognitive abilities.
Describe significant developmental changes in the brain and motor skills during infancy and early childhood.
Explain how an infant's brain starts to process and store memories.

Courtesy of the AP psychology course and exam description, effective fall 2024. (n.d.).

Prenatal Development

Prenatal development begins at conception and occurs in three distinct phases. Conception is the release of the mother's egg and fertilization by one of two hundred million sperm released by the father. Once sperm has penetrated an egg, you have a zygote (the single cell formed at conception from the union of the egg cell and the sperm cell). Once the zygote is formed, you enter the germinal period of development. This phase lasts approximately two weeks. When the zygote is formed, it is no longer than a period at the end of a sentence in a textbook. As a zygote, your cells (a combination of chromosomes from mom and dad) begin to divide rapidly, and your heart begins to beat. During this rapid cell division, some structures that house and protect the developing fetus will form, eventually implanted in the mother's uterine wall. Less than half of all zygotes survive these first two weeks. If the zygote does survive over nine months, the single cell will develop into a newborn baby.

Image of an embryo

The embryonic period is crucial to development. It begins around three weeks and lasts until about eight weeks. The brain is the first major organ to form. The central nervous system begins to create, and the nervous system, legs, arms, eyes, ears, and teeth. During this stage, you start to look human. Genes on your sex chromosomes will trigger the development of your sex organs. Toward the end of this period, your bones begin to form.

The last and longest development phase is called the fetal stage, lasting around nine to thirty-seven weeks. The main task during this time is preparing for life outside the womb. Your organs continue to grow, the fetus increases in size, reflexes begin in preparation for life outside the womb, and you begin to put on fat. By six months of gestation, a fetus has developed sufficiently to potentially survive outside the womb with significant medical assistance, although earlier births require substantial medical intervention. During the final two months, a fetus will double in size with an extra three pounds of fat to prepare for temperature regulation outside of the womb.

During fetal development, the fetus is housed in an amniotic sac and is connected to the mother through the umbilical cord. The umbilical cord acts as a lifeline or filter. Through it the fetus receives nourishment and oxygen, and it is necessary to remove waste.

Teratogens

During prenatal development, many things can go wrong. While the placenta and umbilical cord act as filters to the developing fetus, sometimes harmful agents the mother either ingests or is exposed to travel through the placenta and affect the child in a harmful way. These chemical agents that can harm the prenatal environment are called teratogens. They can cause abnormal development or even birth defects. The earlier the exposure to the teratogen, the more severe the effects.

One typical example is alcohol. Alcohol use during pregnancy can lead to what is called Fetal Alcohol Syndrome (FAS). It is the number one cause of intellectual disability and is present in 1% of all births.

FAS is characterized by physical and cognitive abnormalities. Additionally, it causes damage to the CNS, low birth weight, and behavioral problems.

FAS Facial Characteristics: small eye openings, smooth philtrum, thin upper lip

The Newborn

Infants possess remarkable abilities that researchers study to understand the early stages of cognitive development. One method used is habituation, where infants show decreasing interest with repeated exposure to a stimulus, indicating their ability to recognize familiar patterns. This ability is crucial as babies can exhibit boredom when faced with repetitive stimuli, showcasing their ability to differentiate between sensory inputs. Infants exhibit a preference for stimuli that promote social interaction, such as turning towards human voices and gazing longer at face-like images. These behaviors provide valuable insights into infants' mental abilities and their inclination towards social responsiveness from the earliest stages of life.

Complete the newborn reflexes activity below.

Visual Cliff

Research utilizing the visual cliff apparatus has shown that infants are able to perceive depth early on, which impacts their understanding of the world around them. This innovative tool allows psychologists to assess infant responses and understand how physical development influences cognitive processes and behavior throughout early life. By understanding the connection between physical growth and mental processes in infancy and childhood, we can gain valuable insights into developing crucial cognitive skills and behaviors during this formative period.

Maturation

Physical development in infancy and childhood follows a standard sequence, although the timing of milestones can differ among individuals. Fine and gross motor coordination are critical physical and psychological milestones during this period. As children grow, their motor skills improve, enabling them to gain independence by mastering essential abilities for their development. Maturation is the natural and biological process of changing over time in an individual, independent of any specific environment or social influences. As a result of natural aging, it describes the progression of physical, cognitive, and emotional abilities. Many developmental milestones are influenced by maturity, including motor skills, language acquisition, social development, and abstract thinking. Maturation suggests that, regardless of external factors, individuals undergo inherent and predictable changes throughout their lives.

Brain Development

During infancy, the brain undergoes an extraordinary period of growth and development. While in the mother's womb, the brain rapidly produces nerve cells at a staggering rate of almost a quarter million per minute. By 28 weeks, the number of neurons in the brain reaches its peak. Interestingly, by the time a baby is born, they already have most of the brain cells they will ever have. However, after birth, the brain experiences a burst of growth as neural networks branch out, facilitating the development of various abilities. The most rapid brain growth occurs from three to six years old, particularly in the frontal lobes responsible for planning. Areas associated with thinking, memory, and language are among the last to mature. This developmental process highlights the critical period during which skills such as language acquisition must be nurtured or synaptic pruning will take place. Synaptic pruning is like a "use it or lose it" process in the brain, where unused neural connections are trimmed away while frequently used ones are strengthened, helping the brain work more efficiently.

Motor Development

Throughout infancy, the developing brain plays a crucial role in developing motor skills. These skills are categorized into two main types: fine motor skills, which involve using small muscles in the body, and gross motor skills, which require the coordination of larger muscles for whole-body movements. As infants grow and their muscles and nervous systems mature, they gradually exercise these abilities. While there may be occasional exceptions, fine and gross motor skills development typically follows a universal sequence. For instance, infants will first learn to grasp objects before mastering the art of building towers. Similarly, they will naturally progress from rolling over to sitting up. It is essential to understand that these milestones are not merely based on imitation but are a direct result of the nervous system's maturation process.

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