Stages of Development

Learning Objectives

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

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

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

    • Compare and contrast physical, cognitive, and emotional development that occurs during adolescence

    • Examine physical, cognitive, and emotional development that occurs in adulthood

Lifespan Development Overview

  • Continuous development from birth to death.

  • Development categorized into three areas:

    • Physical Development

    • Cognitive Development

    • Psychosocial Development

  • Development divided into specific stages according to age, mirroring Erikson’s stages:

    • Prenatal

    • Infant

    • Child

    • Adolescent

    • Adult

Prenatal Development

  • The process from conception to birth follows an orderly sequence and consists of three stages:

    • Germinal Stage (Weeks 1–2)

    • Embryonic Stage (Weeks 3–8)

    • Fetal Stage (Weeks 9–40)

Germinal Stage (Weeks 1–2)

  • Conception occurs when sperm fertilizes an egg to form a zygote.

    • Zygote: A one-cell structure with a set genetic makeup and determined sex.

  • Mitosis: The process of cell division that occurs during the first week after conception.

    • E.g., 100 cells after 5 days, billions by 9 months.

  • Less than half of all zygotes survive past the first two weeks.

  • Cells begin to specialize and form organs and body parts before the cells attach to the uterus lining, signaling the start of the embryonic stage.

Embryonic Stage (Weeks 3–8)

  • 7–10 days post-fertilization, the zygote becomes an embryo after implanting in the uterus lining.

    • Development of the placenta begins to provide nourishment and oxygen via the umbilical cord.

  • Early formation of basic structures distinguish head, chest, and abdomen shapes.

  • Key developments:

    • Heart starts beating.

    • Organs form and function begins.

    • Development of the neural tube, which becomes the spinal cord and brain.

Fetal Stage (Weeks 9–40)

  • At 9 weeks, the embryo becomes a fetus, taking on a more human-like shape.

  • Critical Developmental Milestones:

    • 9–12 weeks: Differentiation of sex organs.

    • 16 weeks: Approximately 4.5 inches long with developed fingers and toes.

    • 24 weeks: Weighs up to 1.4 pounds; internal organs are capable of limited function.

    • 36 weeks: Nearly ready for birth, weighing about 6 pounds and measuring 18.5 inches.

  • By 40 weeks, the fetus is fully developed, and labor is imminent.

Prenatal Influences

  • Genetic and Environmental Factors: Significant during all prenatal stages affecting fetal development.

  • Prenatal Care: Vital for monitoring health.

    • Discussing pregnancy planning lifestyle choices with a healthcare provider is essential (e.g., Folic acid intake).

  • Concern about equitable access to prenatal care across populations.

  • Placenta: Transfers everything ingested by the pregnant individual to the fetus [“eating for two”].

  • Teratogens: Any environmental agent causing fetal damage, e.g., alcohol, drugs, certain medications, radiation.

    • Fetal alcohol spectrum disorders (FASD) can occur due to excessive alcohol use in pregnancy, leading to:

    • Low IQ

    • Impulse control issues

    • Learning disabilities

Examples of Teratogens and Their Effects

  • Alcohol: Leading preventable cause of intellectual disabilities.

    • Fetal Alcohol Syndrome Facial Features:

    • Below-average head size, distinct eye opening, low nasal bridge, thin upper lip, indistinct philtrum.

  • Smoking: Reduces blood oxygen levels; associated with premature birth and SIDS.

  • Other Teratogens: Include drugs (heroin, cocaine) and certain infections (HIV, rubella).

  • Specific periods in pregnancy when exposure to teratogens is most harmful are termed critical or sensitive periods.

Reflexes and Sensory Capacities in Infancy

  • Every healthy newborn displays automatic reflexes, crucial for survival, including:

    • Rooting Reflex: Turns head toward cheek stimulation.

    • Sucking Reflex: Automatic sucking motions.

    • Grasping Reflex: Grasping of objects placed in baby's palms.

    • Moro Reflex: Reaction to falling sensations; spreading arms and then pulling them back.

  • Newborn Sensory Abilities:

    • Preferences for faces and human voices utilized for caregiver bonding; can distinguish mothers by scent.

Physical Development from Infancy to Childhood

  • Average weight at birth 7.5 pounds, with rapid growth rates:

    • Weight typically doubles in 6 months, triples in a year, quadruples by age 2.

    • Average length: 19.5 inches at birth, reaching 29.5 inches by 12 months.

  • Significant motor skills development occurring systematically through stages:

    • Head control, sitting, crawling, walking.

  • Brain Growth: 55% of adult size at age 2, reaching 90% by age 6.

  • Follow Piaget's cognitive development sequence, where rapid neural development fuels cognitive advances.

Developmental Milestones for Ages 2–5

Age (years)

Physical Skills

Personal/Social Skills

Language Skills

Cognitive Skills

2

Kicks a ball; walks up and down stairs

Plays alongside others; copies adults

Points to objects; basic sentence structure

Sorts shapes and colors; follows instructions

3

Climbs, runs, pedals tricycle

Takes turns; expresses many emotions

Names familiar objects; uses pronouns

Plays make-believe; uses toys with parts

4

Catches balls; uses scissors

Prefers group play

Knows songs, rhymes; begins writing letters

Names colors and numbers

5

Hops, swings; uses fork and spoon

Distinguishes real from pretend

Speaks in full sentences; counts to 10 or higher

Prints letters; copies basic shapes

Cognitive Development in Early Childhood

  • Piaget's theories critiqued; research shows understanding of objects early on.

    • E.g., infants can infer object properties from mere observations.

  • Cognitive Milestones:

    • Head shaking to indicate “no” around 6–9 months.

    • Understanding object permanence by around 8 months—critical for social interactions (e.g. hide and seek).

  • Developments in language skills:

    • Cooing and babbling transitioning to word formation by 12-18 months, indicating early sentence formation strategies.

Acquisition of Language

  • Children begin gesturing; advancement from cooing to babbling is culturally consistent.

  • By age 3:

    • Vocabulary of up to 1,000 words, capable of simple sentences.

    • Vocabulary Spurt: 10–20 new words a week.

  • Theories of language acquisition:

    • Behaviorist (B.F. Skinner) and Innate capacity (Noam Chomsky).

    • Current consensus suggests a blend of both theories.

Attachment and Psychosocial Development

  • Attachment Theory: Focus on the bond between infants and caregivers.

    • Harlow's monkey studies emphasized comfort over nourishment.

    • Bowlby's Attachment: Proposed the need for a secure base; healthy attachments depend upon caregiver responsiveness and mutual interactions.

  • Ainsworth’s Strange Situation: Identified attachment styles:

    • Secure Attachment: Caregiver responsiveness leads to exploration.

    • Avoidant Attachment: Child disregards the caregiver, showing disinterest.

    • Resistant Attachment: Clinginess combined with rejection of caregiver's interactions.

    • Disorganized Attachment: Erratic behavior; often linked with abuse.

Self-Concept and Milestones

  • Infant self-concept develops through interaction and milestones such as mirror recognition by 18 months.

  • Growth in social interactions and understanding of one’s identity begins as children approach school age; begins comparison with peers.

  • Development of a positive self-concept is crucial for healthy development, influencing confidence and behavior in school.

Adolescence and Its Developmental Stages

  • Physical Development: Puberty signaling the start of adolescence (12-18 years);

    • Includes rapid growth spurts and the maturation of primary/secondary sexual characteristics.

    • Puberty effects vary widely, impacting social dynamics and self-perception significantly.

  • Cognitive Development: Transitioning to abstract and hypothetical thought processes, characterized by a move beyond concrete thinking.

  • Psychosocial Development: Central focus on identity formation—shaped by peer influence, where adolescents explore independence from parents while maintaining connections to them.

Emerging Adulthood

  • Defined as a transitional period (18-mid 20s); varies by culture, exploring work, love, and self-support.

  • Adulthood Stages: Early, Middle, and Late, with distinct characteristics in physical and cognitive abilities.

    • Peak physical abilities in early adulthood, gradual decline in middle adulthood.

    • Cognitive abilities can remain stable but may experience declines in late adulthood, with a focus on maintaining mental and physical activity to mitigate declines.

    • The role of social relationships remains critical for well-being in adulthood.

Summary of Developmental Impacts

  • Healthy aging includes maintaining social connections, engaging in meaningful work, and confronting societal changes around independence.

  • Adverse influences discussed throughout development illustrate the complexities of identity, attachment, and personal growth across the lifespan.