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Developmental Psychology Unit 1: Theories and Research Methods

Developmental psychology studies how people change and stay the same from conception to death. This unit gives you the big theories and the research designs that every later unit relies on.

Covers: The lifespan perspective and domains, Classic developmental debates, Psychoanalytic and psychosocial theories, Learning and social cognitive theories, Piaget, Vygotsky and information processing, Ecological and ethological theories, Research designs and ethics

Study guide

Developmental psychologists study change across the whole lifespan in three broad domains: physical (body, brain, motor skills, health), cognitive (thinking, memory, language, problem solving) and socioemotional (emotions, personality, relationships). The domains interact: a toddler who learns to walk explores more, which feeds cognitive growth and changes how parents respond. Paul Baltes described the lifespan perspective, which holds that development is lifelong, multidirectional (gains and losses happen together), plastic (open to change), multidisciplinary and embedded in history and culture. Influences can be normative age-graded (puberty, retirement), normative history-graded (a pandemic or recession that hits a whole cohort) or non-normative (a lottery win or an early parent death).

Three classic debates organize the field. Nature versus nurture asks how much development reflects genes and biology versus experience; modern researchers stress that the two always interact. Continuity versus discontinuity asks whether change is gradual and quantitative, like a tree growing taller, or happens in qualitatively different stages, like a caterpillar becoming a butterfly. Stage theorists such as Piaget and Erikson favor discontinuity, while learning and information-processing theorists favor continuity. Stability versus change asks whether early traits, such as a shy temperament, persist into adulthood or can be reshaped. Expect test questions that describe a researcher's claim and ask which side of a debate it supports.

The grand theories each take a different angle. Freud's psychoanalytic theory proposed psychosexual stages (oral, anal, phallic, latency, genital) driven by unconscious conflicts. Erik Erikson revised it into eight psychosocial stages, each built around a crisis such as trust versus mistrust or identity versus role confusion, extending development into old age. Behaviorists such as John Watson and B. F. Skinner explained development through classical and operant conditioning, while Albert Bandura's social cognitive theory added observational learning and self-efficacy. Jean Piaget proposed four cognitive stages built through assimilation and accommodation, and Lev Vygotsky emphasized social interaction, the zone of proximal development and scaffolding. Information-processing theory compares the mind to a computer that gains speed and capacity gradually.

Urie Bronfenbrenner's bioecological model places the child within nested systems: the microsystem (family, school), the mesosystem (links between microsystems, such as parent-teacher contact), the exosystem (settings that affect the child indirectly, such as a parent's workplace), the macrosystem (culture, laws, values) and the chronosystem (change over time). Ethological theory, from Konrad Lorenz and John Bowlby, looks at behavior shaped by evolution and at critical or sensitive periods. Evolutionary developmental psychology asks how traits such as attachment helped ancestors survive. A good answer on a test matches a scenario to the theory whose central mechanism best explains it, not just to a famous name.

Research designs answer different questions. Correlational studies show whether two variables are related but cannot show cause, because a third variable may explain both. Experiments randomly assign participants to conditions and manipulate an independent variable, so they can support causal claims. To study age, cross-sectional designs compare different age groups at one time (fast, but confounded by cohort effects), longitudinal designs follow the same people over years (show individual change, but suffer attrition and practice effects), and sequential designs combine both by following several cohorts. Ethical research with children requires parental informed consent, the child's own assent, protection from harm, confidentiality and debriefing.

Key ideas

• Development spans physical, cognitive and socioemotional domains that constantly influence one another.
• Baltes's lifespan perspective treats development as lifelong, multidirectional, plastic, multidisciplinary and contextual.
• Stage theories (Freud, Erikson, Piaget) assume discontinuity; learning and information-processing theories assume continuous change.
• Vygotsky argued that learning is social and happens best within the zone of proximal development with scaffolding.
• Bronfenbrenner's nested systems explain how settings the child never enters, such as a parent's job, still shape development.
• Only true experiments with random assignment support cause-and-effect conclusions.
• Cross-sectional studies risk cohort effects, longitudinal studies risk attrition, and sequential designs reduce both problems.

Formulas and rules

Common mistakes

• Treating a strong correlation as proof that one variable causes the other.
• Confusing the mesosystem (links between two microsystems) with the exosystem (a setting the child is not in).
• Mixing up Freud's psychosexual stages with Erikson's psychosocial stages.
• Calling a study longitudinal when it compares different age groups at a single time point.
• Assuming a negative correlation is weaker than a positive one; r = -0.70 is stronger than r = +0.40.

Before the test, make sure you can

• Explain the three domains of development and the main claims of the lifespan perspective.
• Identify which side of the nature-nurture, continuity-discontinuity and stability-change debates a claim supports.
• Match Erikson's crises and Piaget's stages to their age ranges.
• Distinguish behaviorism, social cognitive theory, Piagetian theory and Vygotsky's sociocultural theory.
• Classify a setting into the correct level of Bronfenbrenner's model.
• Choose the best research design for a question and name its main weakness.
• Interpret the sign and strength of a correlation and explain why it cannot show cause.
• Describe the ethical protections required in research with children.

Words to know

Lifespan perspective

Baltes's view that development is lifelong, multidirectional, plastic, multidisciplinary and shaped by context.

Normative history-graded influence

An event that affects a whole generation at the same time, such as a war or pandemic.

Non-normative influence

An unusual life event that happens to a particular person, such as a serious accident.

Continuity vs. discontinuity

Debate over whether development is gradual and quantitative or occurs in qualitatively distinct stages.

Psychosocial stages

Erikson's eight stages, each centered on a social crisis whose resolution shapes later development.

Social cognitive theory

Bandura's theory that people learn by observing models and that self-efficacy guides behavior.

Assimilation

Piaget's term for fitting new information into an existing schema.

Accommodation

Piaget's term for changing a schema to fit new information.

Zone of proximal development

Vygotsky's range between what a child can do alone and what the child can do with skilled help.

Scaffolding

Support that an adult or more skilled peer adjusts to the learner's level and gradually withdraws.

Microsystem

The settings a person directly participates in, such as family, classroom and peer group.

Exosystem

Settings the person does not enter that still affect them, such as a parent's workplace or a school board.

Chronosystem

The dimension of time in Bronfenbrenner's model, including life transitions and historical change.

Critical period

A fixed window in which an experience must occur for normal development; a sensitive period is a more flexible optimal window.

Cohort effect

A difference between age groups caused by their different historical experiences rather than by age itself.

Attrition

Loss of participants over the course of a longitudinal study, which can bias results.

Sequential design

A design that follows several cohorts over time, combining cross-sectional and longitudinal approaches.

Assent

A child's own agreement to take part in research, sought in addition to parental consent.

Sample practice questions

30 more questions like these, from level 1 to 5, are in the practice set.