Overview of Developmental Psychology

Scientific study of change & continuity across the lifespan

What is Developmental Psychology?

Developmental psychology is the scientific study of how and why people change over time. It explores systematic, age-related changes in physical, cognitive, and socio-emotional domains from conception to late adulthood, emphasising both growth and decline.

For example, developmental psychology explores how:

  • Infants develop motor skills
  • How teenagers form their identities?
  • why older adults maintain or lose cognitive abilities?

Core Questions

  1. Nature vs Nurture – How do genes and environment interact?
  2. Continuity vs Discontinuity – Is change gradual or stage-like?
  3. Stability vs Plasticity – Are early traits enduring or malleable?
  4. Individual vs Context – How do culture, technology, and historical time shape trajectories?

Major Developmental Stages

Foundational terms for understanding lifespan development

Developmental psychologists commonly divide the lifespan into stages defined by age and typical maturational events.
Stage Approx. Age Key Attainments Hallmark Tasks
Prenatal (conception to birth): This period includes the:
  1. Germinal (first 2 weeks)
  2. embryonic (weeks 3–8)
      The embryo/fetus becomes sensitive to environmental factors:
      • Nutrition
      • Toxins
      • Maternal health
  3. Fetal (weeks 9–40) stages of development.
    • The fertilized egg (zygote) undergoes cell division and differentiation.
    • Fundamental organs and body structures form
 Object permanence, goal-directed actions A-not-B task
Infancy 0–2 years Symbolic play, language explosion, egocentrism Three-mountain task
Pre-operational 2 – 7 yrs Symbolic play, language explosion, egocentrism Three-mountain task
Concrete Operational 7 – 11 yrs Conservation, decentration, class inclusion Liquid & clay conservation tasks
Formal Operational 12 yrs + Abstract reasoning, hypothetico-deductive logic Pendulum problem
The major stages are as follows: Formal Operational 12 yrs + Abstract reasoning, hypothetico-deductive logic Pendulum problem . 6–11 years School-aged children grow steadily in height and strength. Cognitive development advances to Piaget’s concrete operational stage: children think logically about concrete information (understanding conservation, categorization). Socially, peer relationships and teamwork become important. Erikson called this the industry vs. inferiority stage, as children gain competence through school and social skills. Developmental research in this period looks at literacy, peer group norms, and the impact of school environments talkspace.com . Adolescence (12–18 years): Marked by puberty, adolescence brings rapid physical changes (growth spurt, sexual maturation). Cognitively, many enter Piaget’s formal operational stage, developing abstract and hypothetical thinking. Social-emotionally, teens face Erikson’s identity vs. role confusion: they explore values, goals and personal identity. Peer influence intensifies and autonomy from parents grows. Adolescents often experience emotional ups and downs due to hormonal changes and social pressures talkspace.com . Early Adulthood (19–40 years): Early adults typically reach peak physical health and strength, though fertility and metabolic health begin gradual declines. Cognitive development stabilizes (many argue development of postformal thought and wisdom). This stage centers on establishing careers, intimate relationships, and family life (Erikson’s stage of intimacy vs. isolation). Success in early adulthood is often measured by achievement of life goals like higher education, employment, marriage, and parenthood talkspace.com . Middle Adulthood (41–65 years): Middle-aged adults experience further aging: visible signs of aging appear, and health risks (e.g. menopause for women) increase. Many maintain cognitive abilities while gaining expertise and practical intelligence. Psychosocially, Erikson’s generativity vs. stagnation involves nurturing the next generation and contributing to society. Adults may reassess life goals and seek purpose (career change, community involvement). Researchers study midlife health, career plateau or changes, and social roles (e.g. caring for aging parents) talkspace.com . Late Adulthood (65+ years): Late adulthood involves significant variability. Physical functioning may decline (strength, sensory acuity, health issues), and neurocognitive changes (some memory slowing, though crystallized intelligence can remain high). Socially and emotionally, individuals cope with retirement, possible widowhood, and reflecting on life (Erikson’s integrity vs. despair). Current research examines aging processes (dementia vs. successful aging), intergenerational relationships, and how to support cognitive and emotional well-being in late life talkspace.com . Each stage is characterized by domain-specific milestones but is also influenced by earlier development. For example, secure infant attachment can affect social relationships in adolescence and beyond. Developmental psychologists study normative changes (shared by most individuals) and individual differences at each stage. (The examples above are drawn from empirical studies and developmental texts courses.lumenlearning.com talkspace.com .)

Theoretical Frameworks

Classic & contemporary models that organise lifespan findings

Theoretical Frameworks & Stage Models

In-depth tables of age ranges, core conflicts, & hallmark achievements

Piaget – Cognitive-Constructivist Stages

Big idea : Children are little scientists who actively build mental models of the world. Development proceeds through four qualitatively different stages, each unlocking new logical operations that let the child think in increasingly abstract ways.

Stage Approx. Age Key Attainments Hallmark Tasks
Sensorimotor 0 – 2 yrs Object permanence, goal-directed actions A-not-B task
Pre-operational 2 – 7 yrs Symbolic play, language explosion, egocentrism Three-mountain task
Concrete Operational 7 – 11 yrs Conservation, decentration, class inclusion Liquid & clay conservation tasks
Formal Operational 12 yrs + Abstract reasoning, hypothetico-deductive logic Pendulum problem

Children progress via assimilation() & accommodation(), constructing increasingly complex schemas.

Erikson – Psychosocial Stages

Big idea : Personality evolves through eight lifespan “crises.” At each age we must balance two opposing forces (e.g. Trust ↔ Mistrust); successful resolution leaves us with a virtue (hope, will, purpose…) that fuels later growth.

# Conflict Virtue Gained Age Span
1 Trust vs Mistrust Hope 0 – 18 m
2 Autonomy vs Shame Will 18 m – 3 yrs
3 Initiative vs Guilt Purpose 3 – 5 yrs
4 Industry vs Inferiority Competence 6 – 11 yrs
5 Identity vs Role Confusion Fidelity 12 – 18 yrs
6 Intimacy vs Isolation Love 18 – 40 yrs
7 Generativity vs Stagnation Care 40 – 65 yrs
8 Integrity vs Despair Wisdom 65 yrs +

Successful resolution produces a psychosocial virtue that scaffolds the next stage.

Big idea : Behaviour is driven by unconscious instinctual energy (libido). As this energy shifts to different body zones across childhood, we face conflicts; how we resolve them shapes adult personality traits.

Freud – Psychosexual Stages

Stage Age Erogenous Focus Fixation Outcome (if unresolved)
Oral 0 – 18 m Mouth, sucking Oral-dependent habits (smoking, overeating)
Anal 18 m – 3 yrs Bladder & bowel control Anal-retentive or expulsive traits
Phallic 3 – 6 yrs Genitals (Oedipal focus) Vanity, recklessness
Latency 6 – 12 yrs Dormant libido Difficulties with intimacy
Genital 12 yrs + Mature sexuality Balanced personality

Freud framed development as resolution of instinctual energy (libido) conflicts; modern views treat it as historical context.

Kohlberg – Moral Reasoning Stages

Big idea : Moral judgment matures in three levels (pre-, conventional, post-) that reflect widening concern—from self-interest to societal rules to universal principles of justice. Progress depends on cognitive growth and social dialogue.

Level Stage Reasoning Focus
Pre-conventional 1. Obedience / Punishment Avoid punishment
2. Instrumental Relativist Self-interest, rewards
Conventional 3. Interpersonal Concordance “Good-boy/girl” approval
4. Law & Order Maintain social order
Post-conventional 5. Social Contract Mutual benefit, rights
6. Universal Ethical Principles Abstract justice / conscience

Progression is not strictly age-bound; few adults reach Stage 6. Moral judgment ≠ moral behaviour.

Bronfenbrenner – Bio-ecological Systems (PPCT)

Big idea : Development is the product of ever-changing interactions (proximal processes) between a person and nested environmental systems—from family to culture to historical era.

  1. Microsystem – family, school, peers
  2. Mesosystem – interactions between microsystems (e.g., parent-teacher)
  3. Exosystem – indirect environments (parent workplace)
  4. Macrosystem – cultural ideologies, laws
  5. Chronosystem – time & historical change (e.g., digital era)

Later PPCT revision emphasises Proximal Processes, Person, Context, Time. No discrete stages but shifts as nested contexts evolve.

Vygotsky – Sociocultural Theory

Big idea : Learning is fundamentally social. Adults and peers “scaffold” the child within the Zone of Proximal Development, and external cultural tools (language, symbols) gradually become internal mental functions.

Development occurs through internalisation() of culturally mediated tools (language, symbols). The Zone of Proximal Development defines the gap between solo ability & guided potential. Staged change is fluid rather than discrete.

Contemporary Stage-Linked Perspectives

  1. Lifespan Cognitive Neuroscience – sensitive periods & neuroplastic “spurts”.
  2. Bowlby & Ainsworth Attachment – pre-attachment → clear-cut → reciprocal.
  3. Loevinger Ego Development – impulsive → autonomous stages.
  4. Arnett (Emerging Adulthood) – 18-25 yrs as distinct exploration stage.

Contemporary Perspectives

  1. Dynamic-Systems & Embodiment
  2. Neuroconstructivism & Sensitive Periods
  3. Life-Course & Aging Theories

Research Designs & Methods

How developmental scientists generate evidence

Longitudinal, Cross-Sectional & Sequential

// pseudocode – accelerated longitudinal design participants = recruit_birth_cohorts(years=[2015,2017,2019]) for wave in range(6): measure(participants, variables=["cognition","pubertyHormones"])

Sequential designs combine the strengths of cross-sectional and longitudinal approaches to separate age, cohort, and period effects.

Microgenetic and Experience-Sampling

High-frequency observations capture moment-to-moment change (e.g., videotaping soilution of a conservation task or smartphone ESM of adolescent mood).

Ethics

Special protections include assent, parental consent, minimal risk protocols, and mandated reporting for vulnerable populations.

Developmental Stages & Milestones

Key physical, cognitive & socio-emotional changes

Prenatal Period (Conception → Birth)

  1. Germinal – rapid cell division, implantation
  2. Embryonic – organogenesis; teratogen sensitivity
  3. Fetal – growth, neural connectivity, fetal learning (e.g., maternal voice)

Infancy & Toddlerhood (0–2 yrs)

Domain 6 mo 12 mo 24 mo
Motor Sits unaided Crawls / cruises Runs, climbs
Cognitive Object permanence emerging First words Symbolic play
Social Social smile Joint attention Self-recognition

Milestones are averages—individual variability is expected.

Early Childhood (3–6 yrs)

  1. Rapid vocabulary growth & “why” questions
  2. Make-believe play supports theory-of-mind
  3. Initiative vs Guilt psychosocial task
  4. Importance of unstructured play for self-regulation

Middle Childhood (7–11 yrs)

  1. Concrete-operational logic; conservation mastered
  2. Industry vs Inferiority; peer acceptance central
  3. Executive-function improvement supports academic skills

Adolescence (12–18 yrs)

  1. Pubertal hormone surge reshapes limbic & prefrontal circuits, elevating risk-taking
  2. Identity vs Role Confusion; exploration of values & sexuality
  3. Digital media exposure linked to impulsivity & sleep disruption

Emerging & Young Adulthood (18–40 yrs)

  1. Neurological maturation plateaus ≈ 25 yrs
  2. Intimacy vs Isolation; establishing career & partnership
  3. Brain remains plastic—skill acquisition, neurogenesis in hippocampus

Middle Adulthood (40–65 yrs)

  1. Generativity vs Stagnation; parenting & mentorship
  2. Crystallised intelligence peaks; slight decline in processing speed
  3. Hormonal transitions (menopause, andropause) influence health

Late Adulthood (65+ yrs)

  1. Integrity vs Despair; life-review fosters wisdom
  2. Selective optimisation with compensation strategies maintain function
  3. Differentiated trajectories: “young-old” vs “old-old” cognitive paths

Special Topics

Cross-cutting issues shaping modern development

Digital-Age Childhood

OECD data show adolescents averaging 49 hrs/week on screens, linked to mental-health risks and cognitive inflexibility; policy recommends family media plans and tech-company accountability.

Neurodiversity & Atypical Paths

Developmental psychopathology frames ADHD, ASD, and learning disorders as variations in brain networks, advocating early intervention and strength-based supports.

Global Health & Equity

WHO emphasises nurturing care (nutrition, security, responsive caregiving) during the first 1000 days to avert inter-generational inequality.