9.3 Stages of Development

Stages of Development

Learning Objectives

  • By the end of this section, students will be able to:

    • Describe the stages of prenatal development and recognize the importance of prenatal care.

    • Discuss physical, cognitive, and emotional development that occurs from infancy through childhood.

    • Discuss physical, cognitive, and emotional development that occurs during adolescence.

    • Discuss physical, cognitive, and emotional development that occurs in adulthood.

Overview of Development

  • Development is continuous from birth until death.

  • Developmental psychologists typically divide human development into three main areas:

    • Physical Development

    • Cognitive Development

    • Psychosocial Development

  • Lifespan development is categorized into stages based on age, following Erikson’s framework, covering:

    • Prenatal

    • Infant

    • Child

    • Adolescent

    • Adult

Prenatal Development

  • Prenatal development unfolds in an orderly sequence from a one-cell structure to birth.

  • There are three stages of prenatal development:

    • Germinal Stage (Weeks 1–2)

    • Embryonic Stage (Weeks 3–8)

    • Fetal Stage (Weeks 9–40)

Germinal Stage (Weeks 1–2)

  • Conception: When sperm fertilizes an egg, forming a zygote (a one-cell structure).

  • Mitosis: The zygote divides into multiple cells (from 1 to billions) over a period of time (e.g., 100 cells by 5 days).

  • Over 50% of zygotes do not survive past the first two weeks of mitosis.

  • Cells begin to specialize to form organs and body parts. Implantation marks the end of this stage.

Embryonic Stage (Weeks 3–8)

  • After 7–10 days (about 150 cells), the zygote implants in the uterine lining, officially becoming an embryo.

  • Placenta Formation: Blood vessels grow, and the placenta connects the embryo to the mother, supplying nutrients and oxygen.

  • Key developments in this stage:

    • Heart begins to beat

    • Development of basic organ systems (e.g., brain via neural tube).

Fetal Stage (Weeks 9–40)

  • At 9 weeks the embryo is referred to as a fetus.

  • Early fetal development includes:

    • Sex organ differentiation by 12 weeks.

    • By 24 weeks, the fetus can weigh around 1.4 pounds and responds to sound.

    • Brain growth during weeks 16 to 28 results in nearly double the size.

    • By 36 weeks, the fetus weighs around 6 pounds and measures 18.5 inches.

    • Fetal development continues until about 40 weeks, reducing movement space; birth becomes imminent.

Prenatal Influences

  • Environmental and genetic factors profoundly influence fetal development.

  • Prenatal Care: Critical for monitoring the health of mother and fetus to reduce risks of complications.

  • Recommendations include:

    • Discuss pregnancy planning with a doctor.

    • Consider folic acid supplementation.

  • Teratogens: Environmental agents (biological, chemical, or physical) that can cause damage during prenatal development. Examples include:

    • Alcohol - Leading preventable cause of mental retardation (Fetal Alcohol Spectrum Disorders - FASD).

    • Other teratogens include nicotine, drugs (e.g., heroin, cocaine), radiation, and viruses.

Fetal Alcohol Spectrum Disorders (FASD)

  • Physical effects: Small head size, abnormal facial features.

  • Cognitive effects: Poor judgment, learning difficulties, low IQ scores.

  • Children born exposed to alcohol may have lifelong developmental problems.

Other Teratogens

  • Nicotine: Reduces fetal blood oxygen levels, associated with low birth weight and SIDS.

  • Other drugs and substances: Can include heroin, cocaine, methamphetamine, and various prescription medicines.

  • Critical Periods: Specific times during which exposure to teratogens can cause developmental issues, such as facial anomalies associated with FASD.

  • Maternal health is crucial, as anything ingested by the mother can affect fetal development.

Infancy Through Childhood

  • Newborn Characteristics:

    • Average weight: ~7.5 pounds; height: ~19.5 inches.

    • Reflexes include rooting, sucking, and grasping reflexes.

    • Reflexes typically decline by 4–5 months.

Physical Development

  • Rapid physical growth occurs in the first years:

    • Birth weight typically doubles by 6 months and triples by 1 year.

    • Growth patterns are not constant; growth slows between 4 and 6 years.

    • Girls experience a growth spurt by 8–9 years; boys follow suit later.

  • Brain Development:

    • All neurons are present at birth (about 100–200 billion).

    • Rapid growth occurs through blooming and pruning in neural connections.

  • Motor Development: Progression from reflexive to voluntary movements including:

    • Holding head up, sitting, crawling, and walking.

    • Fine and gross motor skills develop through milestones (Table 9.4).

Cognitive Development

  • Piaget’s Theory: Cognitive understanding evolves from interacting with the environment.

  • Object Permanence: Understanding that objects continue to exist while not being visible (achieved around 8 months).

  • Language development progresses from cooing to babbling, and first words develop by 12 months.

    • Vocabulary spurt occurs when children learn new words rapidly.

  • B.F. Skinner and Noam Chomsky's theories on language acquisition:

    • Skinner: Language learned through reinforcement.

    • Chomsky: Innate capacity for language (Language Acquisition Device - LAD).

Attachment and Social Development

  • Attachment: Defined as a long-standing emotional bond.

  • Harry Harlow’s Studies: Showed importance of comfort and security in attachment, beyond just nourishment.

  • John Bowlby: Developed attachment theory, defining it as critical for healthy social and emotional development, emphasizing responsive caregiving.

  • Mary Ainsworth’s Strange Situation: Identified attachment styles:

    • Secure Attachment: Child seeks parent for comfort, feels secure.

    • Avoidant Attachment: Little emotional response upon separation/reunion.

    • Resistant Attachment: Clingy yet rejective behavior towards caregiver.

    • Disorganized Attachment: Erratic behavior, often linked to trauma or abuse.

  • Self-Concept Development: Awareness of self begins around 18 months; expands through interactions and comparisons during childhood.

Adolescence

  • Defined roughly as ages 12 to 18, a time for establishing independence and forming identity.

  • Physical changes include:

    • Puberty: Begins with adrenarche and gonadarche; involves growth spurts and development of primary and secondary sexual characteristics.

    • Average ages for menarche (females) and spermarche (males).

Physical Variations

  • Early and late maturation can affect social status and self-esteem.

    • Early-maturing girls may face higher risks for depression and anxiety.

    • Early-maturing boys are often more popular but may engage in risky behaviors.

  • Brain development continues into early adulthood, particularly in the prefrontal cortex, impacting judgment and impulse control.

Cognitive Development

  • Adolescents show improvements in reasoning, abstract thinking, and understanding multiple perspectives.

  • Cognitive Empathy: Develops, allowing greater understanding of others’ thoughts and feelings.

Psychosocial Development

  • Erikson defines the challenge of adolescence as identity vs. role confusion.

  • Teens form identities in relation to peers and may distance themselves from parents.

  • Positive, supportive relationships with parents correlate with better outcomes.

Emerging Adulthood

  • New stage defined from 18 to mid-20s, characterized by identity exploration in love and work.

  • Variations in transitioning into adult roles exists between cultures.

Adulthood

  • Begins approximately at 20 years old, divided into early, middle, and late adulthood.

  • Physical Changes:

    • Early adulthood sees peak physical abilities and potential weight increases due to life changes such as childbirth.

    • Middle adulthood begins gradual physical decline, visible in skin elasticity and fertility shifts.

  • Cognitive Development:

    • Adult cognitive abilities vary; crystallized intelligence remains or increases, while fluid intelligence may decline in later adulthood.

  • Psychosocial Development:

    • Meaning is found through work and relationships, with familial connections leading to greater well-being.

    • Social support maintains importance as individuals age, contributing to lifelong fulfillment.

Conclusion

  • Human development is complex, involving physical, cognitive, and emotional dimensions across the lifespan. Recognizing these stages provides crucial insights for psychologists and caregivers alike, emphasizing the significance of supportive environments at every developmental stage.