Stages of Human Development

PHASES OF DEVELOPMENT

  • Phase: Duration

    • Prenatal: Conception to 8 weeks

    • Fetus: 8 weeks to birth

    • Infancy: Birth to 15 months

    • Toddler: 15 months to 2 ½ years

    • Preschool: 2 ½ years to 6 years

    • Middle years: 6 to 12 years

    • Early adolescence: 12 to 14 years

    • Middle adolescence: 14 to 16 years

    • Late adolescence: 17 to 19 years

    • Young adulthood: 20 to 40 years

    • Middle adulthood: 40 to 65 years

    • Old age or late adulthood: 65 to 74 years (Young-old), Above 75 years (Old-old), Above 85 years (Oldest-old)

PRENATAL/FETAL LIFE

  • After implantation, the egg begins to divide and is known as an embryo.

  • By the end of 8 weeks, the shape is recognizably human and is now called a fetus.

  • Sex Differences: Boys are more vulnerable to developmental damage than girls; female fetuses exhibit greater vigor (possibly due to the second X chromosome).

  • Development of the Nervous System: Arises from the ectoderm.

FETAL LIFE

  • Extensive biological activity occurs in utero:

  • The fetus exhibits behaviors such as sucking on thumb and fingers, folding and unfolding its body.

    • Fetal Presentation:

    • Vertex presentation: Ideal position for birth (head first).

    • Breech presentation: Buttocks or legs first.

  • Behavioral Responses:

    • Fetal movements detected by 16 to 20 weeks; typically quiet when mothers move but become active when mothers rest.

    • By the 18th week, the fetus can hear.

    • Development of Sensory Features:

    • Retinal structures function by 20 weeks.

    • Eyelids open at 7 months, followed by the development of smell and taste.

  • Birth Reflexes:

    • Examples include the grasp reflex (17 weeks), Moro (startle) reflex (25 weeks), and sucking reflex (28 weeks).

INFANCY PERIOD

  • Average newborn weighs about 3,400g (7.5 lb).

  • Gestational Age Risks:

    • Preterm infants are at increased risk for learning disabilities, emotional problems, and child abuse compared to full-term infants (38-40 weeks).

    • Post-mature infants (born more than 2 weeks overdue) may have distinctive physical characteristics (long nails, scanty lanugo).

A. Primitive Reflexes Present at Birth

  • Include rooting reflex, grasp reflex, plantar (Babinski) reflex, knee reflex, abdominal reflexes, and startle reflex (Moro).

  • Most reflexes vanish by the fourth month; Babinski reflex usually disappears by the 12th month.

  • Survival Systems: Breathing, sucking, and swallowing are functional at birth.

  • Perceptual Abilities: Newborns can detect the smell of their mother’s milk and differentiate their mother's voice at 3 days of age.

B. Language and Cognitive Development

  • At birth, infants make noises (crying) but do not vocalize until about 8 weeks with guttural or babbling sounds.

  • At around 2 years, infants begin using symbolic play and language.

C. Emotional and Social Development

  • Infants start imitating facial movements at 3 weeks and develop a social smile by 2 months.

  • The emotional development parallels cognitive development, primarily governed by interactions with caregivers.

TODDLER PERIOD

A. Language and Cognitive Development

  • Vocabulary expands, toddlers can articulate their wants with simple phrases.

  • Engage in symbolic play, demonstrating a cognitive ability to represent and experiment with objects.

B. Emotional and Social Development

  • Increased differentiation of emotions; social referencing occurs where toddlers seek cues from parents on how to respond to events.

C. Sexual Development

  • Awareness of anatomical differences emerges. Gender identity begins manifesting by 18 months.

D. Toilet Training

  • Control of daytime urination should typically be complete by 2½ years; by 4 years, complete control of nighttime urination usually achieved.

E. Parenting Challenges

  • Parents face the challenge of balancing assertiveness with encouragement of autonomy.

PRESCHOOL PERIOD

  • Marked physical and emotional growth occurs; children reach half their adult height by age 3.

  • Mastery of socialization tasks includes bowel control, dressing, and temper control.

A. Language and Cognitive Development

  • Children's thinking is predominantly egocentric and intuitive.

B. Emotional and Social Behavior

  • Children begin to express complex emotions such as love, jealousy, and concern.

C. Sibling Rivalry

  • The birth of a sibling may evoke rivalry and influence sharing and cooperation skills.

D. Play

  • Engagement in pretend games reflects growing awareness of reality and fantasy.

MIDDLE YEARS

A. Language and Cognitive Development

  • Development of complex idea expression and logical exploration begins to dominate.

B. Emotional and Social Behavior

  • Children develop empathy and concern for others, indicating advanced emotional capacities.

C. Best Friend Relationships

  • With the emergence of same-sex friendships by age 10, these relationships are crucial for healthy psychological growth.

D. School Refusal

  • May manifest due to separation anxiety and is not an isolated issue.

E. Sex Role Development

  • Influenced by societal norms and parental expectations, differences between boys and girls affect peer interactions.

CHILDREN AND DIVORCE

  • Divorce impacts children differently depending on age; infants notice changes in parenting style; older children may feel responsible for the divorce.

DIVORCE

  • Children from divorced families often experience long-term emotional and behavioral challenges.

STEPPARENTS

  • Adjusting to a stepparent can be challenging; about 20% of adolescents in blended families express a desire to move out due to adjustment issues.

FAMILY FACTORS IN CHILD DEVELOPMENT

  • Family stability significantly affects children's mental health. Increased family discord correlates with higher incidences of emotional and behavioral issues.

ADVERSE EVENTS

  • Adverse childhood experiences impact development trajectories significantly alongside genetic predispositions.

DAYCARE

  • Daycare has mixed outcomes; children may have advanced cognitive skills but present challenges in assertiveness and toilet training compared to home-reared children.

PARENTING STYLES

  • Different styles of parenting (authoritarian, indulgent, authoritative) lead to varied outcomes in children's self-esteem and social behaviors.

DEVELOPMENT AND EXPRESSION OF PSYCHOPATHOLOGY

  • Early identification of developmental disorders is critical. Issues may not manifest until children face structured environments, like school settings.

REFERENCES

  • Ong, E. (2025). Normal Development & Aging [ppt]. UNP: College of Medicine.