Developmental Psychology: Key Concepts, Theories, and Brain Development

Developmental Psychology

The scientific study of human growth and change across the lifespan — physical, cognitive, social, and emotional.

WEIRD populations

Research is frequently conducted in Western, Educated, Industrialized, Rich, and Democratic societies, limiting generalizability.

Altricial

Human babies are born relatively helpless and require high parental investment for survival and development.

Sensitive periods

It shows when certain environmental inputs (like language or music) have the most lasting impact on development.

Innate knowledge

Plato argued that humans are born with innate knowledge — nature or nurture.

What did John Lock mean by “tabula rasa”?

The mind is a blank slate; experiences shape who we become (nurture).

Active Child Theory

Children play an active role in shaping their own development through their choices and interactions.

Continuity vs. Discontinuity debate

Whether development is gradual (continuous) or occurs in stages (discontinuous).

Sociocultural Context

The social, cultural, and environmental factors (family, peers, culture) that influence development.

Impact of research on child welfare

By informing education, healthcare, and policy decisions that promote well-being.

Stages of prenatal development

Zygote → Embryo → Fetus.

Differentiation

When cells begin to specialize to perform specific functions.

Teratogen

Any environmental agent that can harm the developing fetus (e.g., drugs, alcohol, radiation).

Sensitive periods and teratogens

Certain stages of development are more vulnerable to external damage.

Dutch Famine Study

Prenatal stress and nutrition can have lifelong effects on health — supporting fetal programming theory.

Cephalocaudal development

Growth from head-to-toe.

Proximodistal development

Growth from center to outer extremities.

Genotype

Genetic makeup.

Phenotype

Observable traits.

Epigenetics

The study of how environment affects gene expression without changing DNA sequence.

Heritability

The proportion of variation in traits among individuals that is due to genetic differences.

Endophenotypes

Internal processes (e.g., neural or biochemical markers) that link genes to behavior.

Brain lobes and functions

Frontal (decision-making), Parietal (spatial processing), Occipital (vision), Temporal (hearing & language).

Synaptic pruning

Elimination of unused neural connections to improve brain efficiency.

Experience-expectant vs. experience-dependent plasticity

Expectant = universal experiences (e.g., vision). Dependent = individual learning experiences (e.g., playing piano).

Sensation vs. perception

Sensation = detection of stimuli; Perception = interpretation of those stimuli.

Preferential-looking paradigm

Researchers measure which stimulus an infant looks at longer to infer discrimination or preference.

Perceptual narrowing

Infants start broadly sensitive to all stimuli but focus on familiar ones over time (e.g., own language or faces).

Infant reflexes

Rooting: helps find nipple; Sucking/Swallowing: enables feeding; Moro: startle reflex for protection; Grasping: cling to caregiver.

Motor development

Results from the interaction of neural, physical, and environmental factors.

Motor affordances

Opportunities for action that an environment provides (e.g., a chair affords sitting).

Statistical learning in infants

Recognizing patterns or probabilities in sounds/events to predict future occurrences.

Classical conditioning

Associating two stimuli.

Operant conditioning

Learning through consequences (reinforcement/punishment).

Observational learning

Learning by watching others' actions and outcomes.

Rational learning

Using prior experiences to make sense of new information or predict outcomes.

Speed of Development

The rate at which developmental milestones or changes occur; can vary between individuals and contexts.

Parental Investment

The time, energy, and resources parents devote to raising offspring to increase their chances of survival and success.

Plasticity

The brain's ability to change and adapt through experience, learning, or injury recovery.

Individual Differences

Variations among people within a group.

Group Differences

Compare averages across different groups.

Nature vs. Nurture

The debate over whether development is driven by genetics (nature) or environment and experience (nurture).

Continuity/Discontinuity

Whether development happens gradually (continuous) or in distinct stages (discontinuous).

Mechanisms of Change

The processes (biological, cognitive, emotional) that produce developmental changes.

Reliability

The consistency of a measurement or observation.

Validity

Whether a test or method measures what it claims to measure.

Cross-Sectional Design

Research comparing different age groups at one point in time.

Longitudinal Design

Research that studies the same individuals repeatedly over a period of time.

Conception

The union of sperm and egg to form a zygote.

Zygote

A fertilized egg cell that results from conception.

Embryo

The developing human from 2-8 weeks after conception.

Fetus

The developing human from 9 weeks until birth.

4th Trimester

The first 3 months after birth when infants adjust to life outside the womb.

Teratogens

Harmful substances that can cause birth defects (e.g., alcohol, drugs, infections).

Placenta

An organ that connects the fetus to the mother's uterus, delivering nutrients and removing waste.

Prenatal Stress Models

Theories examining how maternal stress affects fetal development and later health outcomes.

Genes

Segments of DNA that code for traits or proteins.

Transcription and Translation

Processes where DNA is converted to RNA (transcription) and then into proteins (translation).

Genotype and Phenotype

Genotype = genetic makeup; Phenotype = physical expression of genes.

Methylation

A chemical process that turns genes on or off by adding methyl groups to DNA.

Behavioral Genetics

The study of how genetics and environment contribute to behavior.

Quantitative Genetics Research Design

Methods like twin and adoption studies used to estimate genetic influence.

Molecular Genetics Research Design

Studies examining specific genes to understand their roles in traits or behavior.

Inheritance

The passing of genetic traits from parents to offspring.

Dominant-Recessive Patterns

Genetic traits where one allele (dominant) masks another (recessive).

Sex-Linked Inheritance

Traits linked to genes on sex chromosomes (e.g., color blindness).

Polygenic Inheritance

Traits influenced by multiple genes (e.g., height, intelligence).

Frontal Lobe

Brain region involved in planning, decision-making, and movement.

Parietal Lobe

Brain region for touch, spatial awareness, and attention.

Occipital Lobe

Brain region responsible for vision.

Temporal Lobe

Brain region for hearing, memory, and language.

Lateralization

The specialization of brain hemispheres for different functions.

Corpus Callosum

The bundle of nerve fibers connecting the two hemispheres of the brain.

Neuron

A nerve cell that transmits electrical and chemical signals.

Dendrites

Branch-like structures that receive signals from other neurons.

Cell Body

The part of the neuron containing the nucleus; integrates incoming information.

Axons

Long fibers that transmit electrical impulses to other neurons.

Myelin

A fatty sheath around axons that increases signal speed.

Terminal Ends

The tips of axons that release neurotransmitters to communicate with other cells.

Neurogenesis

The creation of new neurons.

Synaptogenesis

The formation of new synaptic connections between neurons.

Plasticity (in brain development)

The brain's ability to reorganize itself in response to experience or injury.

Experience-Expectant Plasticity

Brain development that depends on universal experiences (e.g., visual input).

Experience-Dependent Plasticity

Brain development shaped by individual, unique experiences (e.g., learning music).

Nurture (Acquired Knowledge): Aristotle

The mind is a clear slate; all knowledge comes from experiences.