Concise answer
Developmental items are usually short scenarios that must be matched to a construct within a named theory. Piaget describes cognition in four stages defined by what the child can and cannot yet do; Erikson describes eight psychosocial crises stretching across the whole lifespan; Kohlberg scores the reasoning behind a moral choice, not the choice itself; Vygotsky adds the social scaffolding that Piaget underplayed. Attachment and parenting-style research supply the standard classification schemes, and the cross-sectional versus longitudinal contrast supplies the methodological item that shows up in every developmental section.
Definitions
- Object permanence
- The understanding that objects continue to exist when they cannot be seen, which develops during Piaget's sensorimotor stage.
- Conservation
- The understanding that quantity stays the same when appearance changes; failing it is the hallmark of the preoperational stage, and passing it marks concrete operational thought.
- Egocentrism
- The preoperational child's difficulty taking another person's point of view — a perspective-taking limit, distinct from centration on one salient feature.
- Zone of proximal development
- Vygotsky's term for the band of tasks a learner cannot complete alone but can complete with support from a more capable partner.
- Cohort effect
- A difference between age groups that comes from having grown up in different eras rather than from age itself; the standard threat to cross-sectional developmental research.
Intuition
Piaget's stages are easiest to hold as a list of things the child cannot yet do. In the sensorimotor stage the child cannot hold an object in mind once it is hidden. In the preoperational stage the child can use symbols but cannot mentally reverse an action, so a tall thin glass simply looks like more. In the concrete operational stage the child can reverse and conserve but needs the problem to be about real, tangible things. In the formal operational stage the child can reason about what would be true if something were the case. Each stage is defined by the ceiling, and the exam scenario is always someone bumping into that ceiling.
Kohlberg's levels are about the source of the rule, not about how nice the answer sounds. Preconventional reasoning cites consequences to the self: punishment or reward. Conventional reasoning cites other people and the law: approval, duty, social order. Postconventional reasoning cites principles that could stand above a particular law. Two people who make opposite choices can be scored at the same level, and one choice can be justified at all three.
The cross-sectional versus longitudinal trade-off is a trade of time against confounds. Testing 20-year-olds and 70-year-olds today is fast, but any difference could come from the seventy years of different history the older group lived through. Following one group for fifty years removes that confound and replaces it with attrition and cost.
Concept walkthrough
Start with the field's framing questions, because they organize the answer choices. Development is studied as a lifespan process, and the standard debates are nature versus nurture, whether change is continuous or occurs in discontinuous stages, and whether one universal course fits everyone. Stage theories, by definition, sit on the discontinuous side and generally claim a fixed order.
Piaget's cognitive theory is the most heavily tested. Children build schemata and revise them through assimilation, which fits new experience into an existing schema, and accommodation, which changes the schema to fit the experience. His four stages are sensorimotor (birth to about two), where object permanence develops; preoperational (about two to seven), where symbolic thought and pretend play appear but the child is egocentric, centers on one salient feature, and fails conservation; concrete operational (about seven to eleven), where reversible logical operations apply to tangible material; and formal operational (adolescence onward), where hypothetical and abstract reasoning become possible. Vygotsky's sociocultural account is the standard contrast: development is driven by interaction with more capable partners, and instruction aimed at the zone of proximal development pulls the learner forward.
Erikson recasts development as eight psychosocial crises: trust versus mistrust, autonomy versus shame and doubt, initiative versus guilt, industry versus inferiority, identity versus role confusion, intimacy versus isolation, generativity versus stagnation, and integrity versus despair. Two properties are frequently tested — the theory covers the entire lifespan rather than stopping at adolescence, and each stage is a task to be resolved rather than a skill to be acquired. Kohlberg, working from responses to moral dilemmas, sorted justifications into preconventional (self-interest, punishment and reward), conventional (approval, law, and social order), and postconventional (abstract principle) levels, and the exam's favorite point is that the level is read from the reasoning, never from the decision.
The social side of development supplies two classification schemes. From Ainsworth's Strange Situation come secure attachment (distress at separation, comfort and quick recovery on reunion), avoidant attachment (little distress, indifference on reunion), resistant or ambivalent attachment (extreme distress and both seeking and rejecting contact on reunion), and disorganized attachment (contradictory, confused behavior). Harlow's monkey studies are the standard evidence that contact comfort, not feeding, drives attachment. Baumrind's parenting styles pair demands with responsiveness: authoritative parents are demanding and responsive, authoritarian parents are demanding and unresponsive, and permissive parents are responsive but undemanding.
Finally, developmental questions often turn methodological. Cross-sectional studies compare different age groups at one moment, which is fast and cheap but confounds age with cohort; longitudinal studies follow the same people over time, which isolates change within individuals but costs years and loses participants to attrition. Because these designs are observational, a developmental finding rarely licenses a causal claim — the same caution that governs the correlational items in the measurement section.
After this page, you should be able to
- Assign a described child behavior to the correct Piagetian stage and name the specific construct — object permanence, egocentrism, centration, conservation, or abstract reasoning — that the behavior demonstrates.
- Match an age or life challenge to Erikson's psychosocial crisis for that period and state the two poles of the crisis.
- Score a moral justification at Kohlberg's preconventional, conventional, or postconventional level from the reasoning given rather than the action chosen.
- Classify attachment behavior from a Strange Situation description and distinguish Baumrind's three parenting styles.
- Choose between cross-sectional and longitudinal designs for a stated research goal and name the confound each design risks.
Formulas and assumptions
Piagetian stage ladder
sensorimotor (0-2, object permanence) -> preoperational (2-7, egocentrism, centration, no conservation) -> concrete operational (7-11, reversible logic on concrete material) -> formal operational (11+, abstract and hypothetical reasoning)
Variables
- stage: qualitative mode of thought, entered in a fixed order
- age ranges: approximate norms, not diagnostic cut-offs
Assumptions
- Ordered map of the stages described in OpenStax Psychology 2e Section 9.2, not a quantitative formula.
- Ages are textbook approximations; the exam tests the order and the defining ability, not the boundaries.
Kohlberg level test
reason cites consequences to self = preconventional; reason cites rules, approval, or law = conventional; reason cites principle above law = postconventional
Variables
- reasoning: the justification the person offers
- decision: the action chosen, which does not determine the level
Assumptions
- Levels are scored from the justification only; the same action can be justified at any level.
Parenting style grid
high demand + high responsiveness = authoritative; high demand + low responsiveness = authoritarian; low demand + high responsiveness = permissive
Variables
- demand: level of control and expectation
- responsiveness: warmth and attention to the child's needs
Assumptions
- Baumrind's classification as summarized in OpenStax Psychology 2e Section 9.3.
Developmental design trade-off
cross-sectional: many ages, one time, risks cohort confound; longitudinal: one group, many times, risks attrition
Variables
- cohort effect: difference caused by era of upbringing rather than age
- attrition: loss of participants over the course of a long study
Assumptions
- Both designs are observational; neither by itself establishes that age causes the change.
Worked example
Separating stage from construct in one scenario
A five-year-old watches an experimenter pour water from a short wide glass into a tall narrow glass and insists the tall glass now holds more water. Asked why she thinks her older brother would answer the same way, she says he would, because that is what she thinks. Name the Piagetian stage and the two distinct constructs on display.
- 1Fix the stage from the ability that is missing. The child cannot mentally reverse the pouring, so quantity is not conserved. Failure of conservation places her in the preoperational stage, roughly ages two to seven, which the age of five fits.
- 2Name the construct behind the water error. She judges the amount from one salient dimension — height — and ignores the compensating change in width. That is centration, and it is what produces the conservation failure.
- 3Name the construct behind the answer about her brother. Assuming another person shares her own view is a perspective-taking failure, which is egocentrism, not centration.
- 4Check the near miss. Concrete operational children pass conservation, so the stage above is ruled out by the water judgment itself; sensorimotor is ruled out because she is using language and symbols fluently.
She is in the preoperational stage. The water judgment shows centration and the resulting failure of conservation; the claim about her brother shows egocentrism.
Common traps
- Reading centration and egocentrism as the same thing. Centration is focusing on one dimension of a physical problem; egocentrism is failing to take another person's viewpoint.
- Scoring Kohlberg from the decision rather than the justification; a person who refuses to steal because it is illegal and a person who steals because a life outranks a property law are both making choices, but only the reasoning fixes the level.
- Assuming Erikson's stages stop in adolescence. Three of his eight crises fall in adulthood, and late-adulthood items usually target integrity versus despair.
- Calling a cross-sectional age difference a developmental change; without following the same people, a cohort effect explains the data equally well.
- Confusing resistant attachment with avoidant attachment. Avoidant infants show little distress and ignore the caregiver on reunion; resistant infants are highly distressed and both seek and reject contact.
Related pages and practice
Question depth and domain coverage vary by exam. Practice answers are checked after submission.
Sources
- GRE Subject Test Content and Structure — ETS. Accessed 2026-07-06. Use as a cited source for exam facts; do not imply affiliation or reproduce protected test material.
- Psychology 2e, Section 9.1: What Is Lifespan Development? — OpenStax. Accessed 2026-08-15. OpenStax textbook content is CC BY-NC-SA 4.0; attribute and avoid verbatim reuse beyond short cited references.
- Psychology 2e, Section 9.2: Lifespan Theories — OpenStax. Accessed 2026-08-15. OpenStax textbook content is CC BY-NC-SA 4.0; attribute and avoid verbatim reuse beyond short cited references.
- Psychology 2e, Section 9.3: Stages of Development — OpenStax. Accessed 2026-08-15. OpenStax textbook content is CC BY-NC-SA 4.0; attribute and avoid verbatim reuse beyond short cited references.
Sources and corrections
Sources last checked 2026-08-15Every source cited on this page was checked on the date shown, and we update the page when a source changes. If something looks wrong, tell us and we'll recheck it.