AP Psychology Unit 3 – Developmental Psychology (Fully Explained)

Developmental psychology studies how we change from birth to death physically, cognitively, and socially.

1. Prenatal Development

Development before birth goes:

  • Zygote → Embryo → Fetus

Exposure to teratogens (alcohol, drugs, stress) can harm development, like Fetal Alcohol Syndrome.

2. Infancy & Childhood – Physical Development

Babies are born with reflexes (rooting, sucking, grasping).
Motor skills develop in order (sit → crawl → walk).
The brain overproduces connections, then prunes unused ones.
Some abilities require critical periods (like language).

3. Cognitive Development – Piaget (How Thinking Changes)

Schemas

Schemas are mental frameworks — basically how we organize information about the world.
Example: a child’s “dog” schema might be “four legs, furry, barks.”

Assimilation

When you fit new information into an existing schema.
Example: calling a wolf a dog.

Accommodation

When you change or create a new schema because the old one doesn’t work.
Example: learning wolves and dogs are different.

Piaget’s Stages

  • Sensorimotor (0–2): learn through senses, develop object permanence

  • Preoperational (2–7): use symbols, egocentric, no conservation

  • Concrete Operational (7–11): logical thinking, conservation

  • Formal Operational (12+): abstract thinking

Kids move through these stages by assimilation and accommodation.

4. Social Development – Erikson’s Psychosocial Stages (Age Conflicts)

At each age, people face a major emotional challenge:

  • 0–1: Trust vs. Mistrust

  • 1–3: Autonomy vs. Shame

  • 3–6: Initiative vs. Guilt

  • 6–12: Industry vs. Inferiority

  • 12–18: Identity vs. Role Confusion

  • 18–40: Intimacy vs. Isolation

  • 40–65: Generativity vs. Stagnation

  • 65+: Integrity vs. Despair

5. Attachment

Attachment is the emotional bond between infant and caregiver.
Harlow proved contact comfort matters more than food.
Ainsworth identified attachment styles (secure vs. insecure).

6. Parenting & Temperament

Temperament is inborn (easy, difficult, slow-to-warm-up).
Parenting styles:

  • Authoritative (best)

  • Authoritarian

  • Permissive

  • Neglectful

7. Adolescence

Puberty happens before the brain finishes developing (frontal lobe), leading to impulsive behavior.
Main goal: identity formation (Erikson).

8. Adulthood & Aging

People focus on relationships, purpose, and reflection.
Crystallized intelligence increases, fluid decreases.

9. Moral Development – Kohlberg

  • Preconventional (punishment)

  • Conventional (rules)

  • Postconventional (ethics)

ONE-SENTENCE SUMMARY (AP TEST READY):

We develop across the lifespan through schemas, assimilation, accommodation, attachment, and psychosocial challenges, shaped by both biology and experience.