Plain-language explanation.
Developmental psychology studies how people change across the lifespan — from birth through old age, examining cognitive, emotional, social, and physical development.
Core concepts and standard treatment.
Core developmental psychology covers Piaget (sensorimotor — object permanence; preoperational — egocentrism, conservation; concrete operational — logical operations; formal operational — abstract reasoning; schema, assimilation, accommodation, equilibration; underestimated infant abilities critique — Baillargeon), Vygotsky (ZPD — zone of proximal development; scaffolding — Wood, Bruner, Ross; MKO — more knowledgeable other; inner speech; language as tool for thought), attachment theory (Bowlby — monotropy, safe haven, secure base, internal working models; Ainsworth Strange Situation — secure, avoidant, ambivalent, disorganised; adult attachment — AAI), and moral development (Piaget — heteronomous vs autonomous morality; Kohlberg — pre-conventional, conventional, post-conventional; Gilligan — ethics of care; Haidt — moral intuition — social intuitionist model).
Deeper theory, debates and edge cases.
Advanced developmental psychology covers neurodevelopment (synaptogenesis — synaptic pruning — myelination — PFC late maturation; sensitive vs critical periods — Lenneberg language hypothesis; executive function development — Miyake; theory of mind — false belief task — Wimmer and Perner; autism and ToM — Baron-Cohen; Bronfenbrenner ecological systems theory — microsystem, mesosystem, exosystem, macrosystem, chronosystem), adolescence (Erikson — identity vs role confusion; Marcia — identity statuses — diffusion, foreclosure, moratorium, achievement; Arnett — emerging adulthood; Steinberg — dual systems model — limbic vs prefrontal risk-taking), and ageing (selective optimisation with compensation — Baltes; cognitive ageing — processing speed — Salthouse; wisdom — Staudinger; dementia — Alzheimer's — amyloid cascade; advance care planning).
How it is applied in practice.
At the developmental psychologist level, practitioners contribute to Child Development; lead longitudinal research (ALSPAC Bristol cohort; Millennium Cohort Study UCL; ABCD Study US adolescent brain; Dunedin Multidisciplinary Study); design early intervention (Sure Start evaluation — NESS; Perry Preschool — Heckman cost-benefit; Incredible Years — Webster-Stratton RCT; Triple P parenting programme); advise on SEND (EHCP — Education, Health and Care Plan; neurodiversity — autism, ADHD, dyslexia; inclusive education — UNESCO Salamanca); and contribute to youth justice (adolescent brain maturity — sentencing reform; YOT — youth offending teams; trauma-informed PACE — DDP — Daniel Hughes).