I. Foundations of Developmental Psychology
1. What Is Development & Child Development
● Development
○ Systematic, organized changes over time in:
■ Physical body: size, brain, motor skills, puberty.
■ Cognition: thinking, reasoning, memory, language.
■ Emotion & social behavior: relationships, regulation, personality.
○ Includes:
■ Growth (gains, improvements).
■ Decline (aging, sensory loss) later in life.
● Child Development
○ Focus = conception through adolescence.
○ Goal = understand:
■ How children change (trajectories).
■ Why they change (biological, cognitive, social, cultural, historical causes).
2. Major Themes & Classic Theorists
2.1 Nature vs Nurture – Classic Thinkers
● Plato – Nature
○ Children born with innate ideas and knowledge.
○ Education = helping them “remember” or express what’s already inside.
● Aristotle – Nurture
○ Children’s minds shaped by experience.
○ No built-in ideas; observation and environment build knowledge.
● John Locke – Nurture, “Tabula Rasa”
○ Newborn = blank slate.
○ All traits, behaviors, and knowledge come from:
■ Parenting.
■ Education.
■ Life experiences.
○ Emphasizes discipline, habits, training.
● Jean-Jacques Rousseau – Nature + “Natural Goodness”
○ Children are innately good.
○ Development unfolds naturally, like plants growing.
, ○ Adults should interfere as little as possible; follow the child’s lead.
● John Watson – Behaviorist (Extreme Nurture)
○ Claimed with full control of environment he could train any healthy infant into any kind
of specialist.
○ Focused only on observable behavior.
○ Learning through conditioning and reinforcement.
2.2 Quantitative vs Qualitative Change
● Quantitative Change
○ Gradual, continuous change in amount:
■ Height, weight.
■ Vocabulary size.
■ Memory span.
○ Same underlying process; just more or less of it.
● Qualitative Change
○ Change in kind or structure:
■ New ways of thinking (e.g., Piaget’s stages).
■ Nonverbal → using language.
■ Concrete thinking → abstract thinking.
○ Stage-like: distinct shifts rather than smooth.
2.3 Sociocultural Context
● Sociocultural context = the broad environment shaping development:
○ Historical time:
■ Growing up pre-internet vs post-smartphone.
■ COVID-era vs pre-COVID.
○ Physical surroundings:
■ Urban vs rural.
■ Noise, crowding, pollution, neighborhood safety.
○ Socioeconomic status (SES):
■ Income, education, occupation, neighborhood.
■ Affects nutrition, healthcare, schooling quality, stress, enrichment.
● Explains why same-age kids can look totally different in skills and outcomes.
,II. Research Methods in Developmental
Psychology
3. Scientific Method
1. Form a research question.
2. Review past research/theories.
3. Form a hypothesis (testable prediction).
4. Design a study (participants, measures, procedures).
5. Collect data.
6. Analyze with statistics.
7. Interpret results (support vs contradict hypothesis).
8. Report findings (papers, talks).
9. Replicate/extend to see if it holds up.
4. Key Example: Romanian Adoption Study
● Children raised in extremely deprived orphanages (minimal caregiving, stimulation).
● Adopted into nurturing families at different ages:
○ Adopted earlier (e.g., before ~6 months):
■ Better recovery in IQ, social behavior, attachment.
○ Adopted later (e.g., after ~2 years):
■ More persistent cognitive, emotional, social problems.
● Takeaways:
○ Sensitive periods matter: timing of experience is crucial.
○ Early severe deprivation can have long-lasting effects, but early intervention helps.
5. Research Strategies: Correlational & Experimental
5.1 Correlational Research
● Goal: examine relationships between naturally occurring variables.
● Correlation coefficient r:
○ Range: -1 to +1.
○ Positive (r > 0): both go up or down together (e.g., study time & grades).
○ Negative (r < 0): one up, one down (e.g., stress & sleep quality).
○ r ≈ 0: no linear relationship.
● Correlation ≠ causation:
, ○ Direction problem: X → Y or Y → X?
○ Third-variable problem: Z (e.g., parenting style) affects both X and Y.
5.2 Experimental Research
● Goal: test causality by manipulating one variable.
● Key parts:
○ Independent Variable (IV): the thing you change (e.g., teaching method).
○ Dependent Variable (DV): the outcome you measure (e.g., test score).
○ Control Group: no manipulation or baseline treatment.
○ Random Assignment: participants randomly assigned to conditions → balances
pre-existing differences, increases internal validity.
● Types of Experiments:
○ Lab Experiments:
■ High control, strong causal claims.
■ Low realism/generalizability (artificial situation).
○ Field Experiments:
■ Manipulation in real-world settings (schools, homes).
■ More realistic, but less control.
○ Natural/Quasi-Experiments:
■ Groups created by events or policies, not random assignment (e.g., different
schools, laws).
■ Realistic but weaker causal claims.
5.3 Reliability & Validity
● Reliability = consistency.
○ Test-retest: same person, similar score across time.
○ Inter-rater: different observers give similar ratings.
● Validity = does it measure what it claims to measure?
○ A “reading test” that mostly measures IQ, not reading, has low validity for reading.
○ A measure can be reliable but not valid (consistently wrong).
6. Designs for Studying Development Over Time
● Cross-sectional:
○ Different ages measured at one time (5 vs 10 vs 15).
○ Pros: quick, cheap.
○ Cons: cohort effects — differences might be due to generation, not age.
● Longitudinal:
○ Same individuals tracked over time.
○ Pros: shows true developmental change and individual trajectories.
1. What Is Development & Child Development
● Development
○ Systematic, organized changes over time in:
■ Physical body: size, brain, motor skills, puberty.
■ Cognition: thinking, reasoning, memory, language.
■ Emotion & social behavior: relationships, regulation, personality.
○ Includes:
■ Growth (gains, improvements).
■ Decline (aging, sensory loss) later in life.
● Child Development
○ Focus = conception through adolescence.
○ Goal = understand:
■ How children change (trajectories).
■ Why they change (biological, cognitive, social, cultural, historical causes).
2. Major Themes & Classic Theorists
2.1 Nature vs Nurture – Classic Thinkers
● Plato – Nature
○ Children born with innate ideas and knowledge.
○ Education = helping them “remember” or express what’s already inside.
● Aristotle – Nurture
○ Children’s minds shaped by experience.
○ No built-in ideas; observation and environment build knowledge.
● John Locke – Nurture, “Tabula Rasa”
○ Newborn = blank slate.
○ All traits, behaviors, and knowledge come from:
■ Parenting.
■ Education.
■ Life experiences.
○ Emphasizes discipline, habits, training.
● Jean-Jacques Rousseau – Nature + “Natural Goodness”
○ Children are innately good.
○ Development unfolds naturally, like plants growing.
, ○ Adults should interfere as little as possible; follow the child’s lead.
● John Watson – Behaviorist (Extreme Nurture)
○ Claimed with full control of environment he could train any healthy infant into any kind
of specialist.
○ Focused only on observable behavior.
○ Learning through conditioning and reinforcement.
2.2 Quantitative vs Qualitative Change
● Quantitative Change
○ Gradual, continuous change in amount:
■ Height, weight.
■ Vocabulary size.
■ Memory span.
○ Same underlying process; just more or less of it.
● Qualitative Change
○ Change in kind or structure:
■ New ways of thinking (e.g., Piaget’s stages).
■ Nonverbal → using language.
■ Concrete thinking → abstract thinking.
○ Stage-like: distinct shifts rather than smooth.
2.3 Sociocultural Context
● Sociocultural context = the broad environment shaping development:
○ Historical time:
■ Growing up pre-internet vs post-smartphone.
■ COVID-era vs pre-COVID.
○ Physical surroundings:
■ Urban vs rural.
■ Noise, crowding, pollution, neighborhood safety.
○ Socioeconomic status (SES):
■ Income, education, occupation, neighborhood.
■ Affects nutrition, healthcare, schooling quality, stress, enrichment.
● Explains why same-age kids can look totally different in skills and outcomes.
,II. Research Methods in Developmental
Psychology
3. Scientific Method
1. Form a research question.
2. Review past research/theories.
3. Form a hypothesis (testable prediction).
4. Design a study (participants, measures, procedures).
5. Collect data.
6. Analyze with statistics.
7. Interpret results (support vs contradict hypothesis).
8. Report findings (papers, talks).
9. Replicate/extend to see if it holds up.
4. Key Example: Romanian Adoption Study
● Children raised in extremely deprived orphanages (minimal caregiving, stimulation).
● Adopted into nurturing families at different ages:
○ Adopted earlier (e.g., before ~6 months):
■ Better recovery in IQ, social behavior, attachment.
○ Adopted later (e.g., after ~2 years):
■ More persistent cognitive, emotional, social problems.
● Takeaways:
○ Sensitive periods matter: timing of experience is crucial.
○ Early severe deprivation can have long-lasting effects, but early intervention helps.
5. Research Strategies: Correlational & Experimental
5.1 Correlational Research
● Goal: examine relationships between naturally occurring variables.
● Correlation coefficient r:
○ Range: -1 to +1.
○ Positive (r > 0): both go up or down together (e.g., study time & grades).
○ Negative (r < 0): one up, one down (e.g., stress & sleep quality).
○ r ≈ 0: no linear relationship.
● Correlation ≠ causation:
, ○ Direction problem: X → Y or Y → X?
○ Third-variable problem: Z (e.g., parenting style) affects both X and Y.
5.2 Experimental Research
● Goal: test causality by manipulating one variable.
● Key parts:
○ Independent Variable (IV): the thing you change (e.g., teaching method).
○ Dependent Variable (DV): the outcome you measure (e.g., test score).
○ Control Group: no manipulation or baseline treatment.
○ Random Assignment: participants randomly assigned to conditions → balances
pre-existing differences, increases internal validity.
● Types of Experiments:
○ Lab Experiments:
■ High control, strong causal claims.
■ Low realism/generalizability (artificial situation).
○ Field Experiments:
■ Manipulation in real-world settings (schools, homes).
■ More realistic, but less control.
○ Natural/Quasi-Experiments:
■ Groups created by events or policies, not random assignment (e.g., different
schools, laws).
■ Realistic but weaker causal claims.
5.3 Reliability & Validity
● Reliability = consistency.
○ Test-retest: same person, similar score across time.
○ Inter-rater: different observers give similar ratings.
● Validity = does it measure what it claims to measure?
○ A “reading test” that mostly measures IQ, not reading, has low validity for reading.
○ A measure can be reliable but not valid (consistently wrong).
6. Designs for Studying Development Over Time
● Cross-sectional:
○ Different ages measured at one time (5 vs 10 vs 15).
○ Pros: quick, cheap.
○ Cons: cohort effects — differences might be due to generation, not age.
● Longitudinal:
○ Same individuals tracked over time.
○ Pros: shows true developmental change and individual trajectories.
