Ch7. Developmental Psychology — The Mind from Birth to Old Age

What Is Developmental Psychology?

Developmental psychology studies how human beings change from birth to death — physically, cognitively, emotionally, and socially.

Core questions:
- Is development continuous or does it proceed in stages?
- Which matters more: genes (nature) or environment (nurture)?
- What drives change?

Piaget’s Stages of Cognitive Development

Jean Piaget argued that children actively construct knowledge rather than passively receive it.

Stage 1: Sensorimotor (0–2 years)
→ Exploring the world through senses and movement
→ Key milestone: object permanence (things still exist when out of sight)

Stage 2: Preoperational (2–7 years)
→ Language development, symbolic thinking
→ Egocentrism: difficulty seeing things from another's perspective

Stage 3: Concrete Operational (7–11 years)
→ Logical thinking about concrete objects (conservation achieved)
→ Able to classify and seriate

Stage 4: Formal Operational (12+ years)
→ Abstract and hypothetical reasoning
→ Scientific thinking develops

Erikson’s Psychosocial Stages

Erik Erikson proposed eight stages of development spanning the entire lifespan.

Stage	Age	Core Conflict	Successful Outcome
1	0–1 yr	Trust vs. Mistrust	Hope
2	1–3 yrs	Autonomy vs. Shame	Will
3	3–6 yrs	Initiative vs. Guilt	Purpose
4	6–12 yrs	Industry vs. Inferiority	Competence
5	Adolescence	Identity vs. Role Confusion	Fidelity
6	Young adulthood	Intimacy vs. Isolation	Love
7	Middle adulthood	Generativity vs. Stagnation	Care
8	Late adulthood	Ego Integrity vs. Despair	Wisdom

Attachment Theory

John Bowlby’s attachment theory: the emotional bond between an infant and caregiver forms the foundation for all subsequent development.

Mary Ainsworth's Attachment Styles (Strange Situation Procedure):

Secure Attachment (~60%):
- Distressed when caregiver leaves; quickly comforted when they return
- Forms when caregivers are consistently responsive

Anxious-Ambivalent Attachment (~20%):
- Extremely distressed on separation
- Angry and clingy even after reuniting

Avoidant Attachment (~15%):
- Little distress on separation or reunion
- Forms when caregivers are consistently rejecting or emotionally unavailable

Disorganized Attachment (~5%):
- No consistent strategy
- Associated with abuse or neglect

Language Development

0–6 months:  Babbling begins
12 months:   First words (mama, dada)
18–24 months: Vocabulary explosion — rapid word acquisition
2 years:     Two-word phrases ("more milk," "daddy go")
3–4 years:   Beginning to apply grammatical rules
5 years:     Near-adult sentence construction

Chomsky's Language Acquisition Device (LAD):
→ Humans are born with an innate capacity for language learning
→ Evidence of a universal grammar underlying all human languages

Adolescence — Identity Formation

Marcia's Identity Status Theory:

Identity Achievement: exploration followed by commitment
→ The healthiest status

Identity Moratorium: actively exploring, no commitment yet
→ Stressful but a sign of healthy development

Identity Foreclosure: commitment without exploration (adopts parents' values)
→ Prone to rigidity

Identity Diffusion: neither exploring nor committing
→ Associated with developmental difficulties

Adulthood and Old Age

Early adulthood (20s–30s):
- Forming intimate relationships (Erikson Stage 6)
- Establishing occupational identity
- Brain plasticity remains high

Middle adulthood (40s–50s):
- Generativity vs. stagnation
- Midlife reappraisal: reassessing life meaning
- Crystallized intelligence increases (experience-based problem solving)

Late adulthood (60s+):
- Ego integrity: accepting one's life as a whole
- Crystallized intelligence maintained; fluid intelligence declines
- Socioemotional selectivity theory: focus narrows to meaningful relationships

Piaget: sensorimotor → preoperational → concrete operational → formal operational Erikson: 8 conflicts — trust, autonomy, initiative, industry, identity, intimacy, generativity, integrity Attachment styles: secure (60%) / anxious (20%) / avoidant (15%) / disorganized (5%) Fluid intelligence declines with age; crystallized intelligence grows with experience