Unit 3.1: Themes and Methods in Developmental Psychology

Aspects That Tend to Show STABILITY:

• Temperament: Basic emotional reactivity patterns established early in life
• Core personality traits: Five-factor model traits (openness, conscientiousness, extraversion, agreeableness, neuroticism)
• Intelligence: Relative ranking on cognitive abilities tends to remain stable
• Attachment patterns: Early relationship styles often persist

Areas That Typically Show CHANGE:

• Physical abilities: Strength, speed, sensory acuity change with age
• Cognitive skills: Knowledge, expertise, wisdom accumulate over time
• Social roles: Student → employee → parent → retiree
• Emotional regulation: Ability to manage emotions typically improves
• Attitudes and beliefs: Often shift with experiences and maturity

NATURE (Biological/Genetic Influences):

• Heredity: Traits passed from parents through genes
• Maturation: Biologically programmed sequences of growth (walking, puberty)
• Temperament: Innate personality tendencies
• Physical characteristics: Height potential, eye color, predispositions
• Brain structure: Neural organization and development patterns

NURTURE (Environmental/Experiential Influences):

• Parenting and family dynamics: Caregiving styles and relationships
• Culture and society: Values, norms, expectations
• Education and learning: Formal and informal instruction
• Nutrition and healthcare: Physical environment quality
• Life experiences: Trauma, enrichment, opportunities

Modern Understanding: Interaction Model

Contemporary psychologists recognize that nature and nurture work together interactively. Genes provide potential ranges, but environment determines where within that range development occurs. Example: Genetic potential for height is influenced by nutrition; genetic predisposition for intelligence is expressed differently based on educational opportunities.

CONTINUOUS Development (Gradual Change)

Development is a smooth, ongoing process like climbing a ramp — changes are quantitative (more of the same).

Characteristics:

• Gradual, incremental changes over time
• No clear boundaries between developmental phases
• Skills build upon each other steadily
• Differences are matters of degree, not kind

Examples: Height/weight growth, vocabulary expansion, gradual improvement in motor skills

DISCONTINUOUS Development (Stage-Like Change)

Development occurs in distinct stages like climbing stairs — changes are qualitative (different kinds of thinking/behavior).

Characteristics:

• Development occurs in distinct, identifiable stages
• Each stage has unique characteristics and capabilities
• Transitions between stages are relatively abrupt
• Earlier stages provide foundation for later ones
• Cannot skip stages in the sequence

Examples: Piaget's cognitive stages (sensorimotor → preoperational → concrete operational → formal operational), Erikson's psychosocial stages, Kohlberg's moral development stages

How It Works:

Researchers study multiple age groups (e.g., 20-year-olds, 40-year-olds, and 60-year-olds) all at the same time and compare their performance on various measures.

Example: Testing memory in groups of participants aged 20, 40, 60, and 80 years old — all tested in 2025.

✅ ADVANTAGES:

• Quick results: Data collected at one time point
• Cost-effective: Less expensive than longitudinal studies
• Large sample sizes: Easier to recruit many participants
• No attrition: Participants don't drop out over time
• No practice effects: Participants only tested once
• Useful for: Identifying age differences and patterns

❌ DISADVANTAGES:

• Cohort effects (MAJOR LIMITATION): Differences between age groups may reflect generational experiences rather than true developmental changes
• Cannot track individual change: Only shows group differences, not how individuals develop
• No causal inferences about development: Can't determine if aging causes differences
• Doesn't show stability vs. change over time

How It Works:

Researchers recruit a group of participants and test them multiple times over months, years, or even decades as they age.

Example: Testing the same group of people at ages 20, 30, 40, 50, and 60 to track how their memory changes over 40 years.

✅ ADVANTAGES:

• Tracks true individual change: Shows how the same people develop over time
• Controls for cohort effects: All participants share the same generational experiences
• Reveals patterns of stability vs. change: Best for determining which traits persist vs. shift
• Better causal understanding: Can see how earlier experiences affect later outcomes
• Rich, detailed data: Deep understanding of developmental trajectories
• Tests continuous vs. discontinuous development: Can identify gradual changes or stage-like shifts

❌ DISADVANTAGES:

• Time-consuming: Takes years or decades to complete
• Very expensive: Requires long-term funding and resources
• Attrition (dropout): Participants move away, lose interest, or die before study completion
• Practice effects: Repeated testing may improve performance artificially
• Outdated measures: Tests designed at study start may become obsolete
• Limited to one cohort: Results may not generalize to other generations

How It Works:

Researchers recruit several age cohorts and follow each group over time, then compare both within-group changes and between-group differences.

Example: Recruit 20-, 30-, and 40-year-olds in 2025, then test all three groups again in 2030 (when they're 25, 35, and 45) and in 2035 (when they're 30, 40, and 50).

✅ ADVANTAGES:

• Reduces cohort effects: Multiple cohorts allow comparison across generations
• Faster than pure longitudinal: Don't have to wait entire lifespan
• Tracks individual change: Still follows people over time
• More comprehensive: Combines strengths of both methods