Developmental psychology asks how people change across the lifespan. To answer, you must compare people of different ages — and there are exactly two ways to do it.
| Design | How it works | Strength | Characteristic flaw |
|---|---|---|---|
| Cross-sectional | Compare different people of different ages at one time | Fast, cheap | Cohort effect — age groups differ by generation (education, nutrition, era), not just age |
| Longitudinal | Follow the same people over many years | Cleanly separates aging from generation | Attrition — dropouts leave a biased (often healthier, more motivated) sample; slow and expensive |
A cross-sectional "decline with age" may really be a generational difference; a longitudinal "modest decline" may reflect the unusually hardy people who stuck around. Every design question on the exam turns on matching the design to its flaw.
Development begins at conception. The fertilized egg is a zygote (roughly the first two weeks); from about two weeks to two months it is an embryo, when the major organs form; from about nine weeks to birth it is a fetus. Memorize the order: zygote → embryo → fetus.
A teratogen is any agent that crosses the placenta and harms prenatal development — alcohol, nicotine, certain viruses and drugs, radiation. Timing matters: the embryonic period, when organs are forming, is the window of greatest vulnerability. The classic example is heavy prenatal alcohol exposure, which can produce fetal alcohol syndrome — physical abnormalities and lifelong cognitive deficits. Newborns arrive with survival reflexes already installed: rooting (cheek stroke → head turns, mouth opens), sucking, grasping, and the Moro (startle) response.
Attachment is the deep emotional bond between infant and caregiver. Harry Harlow (1958) raised infant monkeys with two surrogate "mothers": a bare wire cylinder that dispensed milk and a soft terrycloth cylinder that gave no food. The monkeys clung to the cloth mother nearly around the clock, visiting the wire mother only to feed — and ran to the cloth mother when frightened. Attachment is built on contact comfort, not nourishment. This overturned the "cupboard theory" that infants love whoever feeds them.
Mary Ainsworth measured attachment with the strange situation: a caregiver and infant enter an unfamiliar room, the caregiver leaves and returns, and researchers watch the reunion.
Two normal fears mark a formed attachment: stranger anxiety (about 8 months) and separation anxiety (peaking around 13–15 months).
Diana Baumrind mapped parenting on two axes — warmth and demand:
| Style | Warmth | Demand | Signature |
|---|---|---|---|
| Authoritative | High | High | Firm rules with explanation and responsiveness — best child outcomes |
| Authoritarian | Low | High | "Because I said so" — control without warmth |
| Permissive | High | Low | Loving but few limits |
| Uninvolved (neglectful) | Low | Low | Disengaged on both fronts |
The trap pair is authoritative vs. authoritarian: authoritative parents authorize with reasons and warmth; authoritarian parents are autocrats.
Jean Piaget argued children think in qualitatively different ways at different ages, building schemas (mental frameworks) through assimilation (fitting new information into an existing schema) and accommodation (changing the schema to fit reality).
| Stage | Age | Milestone / limitation |
|---|---|---|
| Sensorimotor | 0–2 | Knows the world through senses and actions; achieves object permanence (objects exist when unseen) |
| Preoperational | 2–7 | Language and pretend play, but egocentrism (cannot take another's perspective), animism, and failure of conservation |
| Concrete operational | 7–11 | Conservation mastered (quantity survives changes in shape), powered by reversibility — but logic works only on tangible things |
| Formal operational | 12+ | Abstract, hypothetical "what if" reasoning |
Conservation is the signature test: pour juice from a short, wide glass into a tall, narrow one and the preoperational child says the tall glass holds more, because she centers on height and ignores width. Note the trap: a 4-year-old who fails the juice task lacks conservation, not object permanence (that arrived in infancy).
Lev Vygotsky emphasized social and cultural guidance. His zone of proximal development (ZPD) is the gap between what a learner can do alone and what she can do with help from a more skilled person. Scaffolding is the temporary support the helper provides, gradually withdrawn as competence grows. Piaget's child is a lone scientist; Vygotsky's child is an apprentice — "with help" in a scenario almost always signals Vygotsky.
Lawrence Kohlberg scored the reasoning behind moral choices (famously about the Heinz drug-stealing dilemma), never the verdict itself:
The same verdict ("he should steal it") can appear at every level with different reasoning. Score the why.
Erik Erikson proposed eight conflicts spanning the whole lifespan:
| Age | Conflict |
|---|---|
| Infancy | Trust vs. mistrust |
| Toddlerhood | Autonomy vs. shame and doubt |
| Preschool | Initiative vs. guilt |
| Childhood (6–12) | Industry vs. inferiority |
| Adolescence | Identity vs. role confusion |
| Young adulthood | Intimacy vs. isolation |
| Middle adulthood | Generativity vs. stagnation |
| Late adulthood | Integrity vs. despair |
The exam grills the middle pair hardest: adolescence is about who am I (identity); young adulthood is about can I commit to another person (intimacy). You must know the I before you can build the us.
Adolescence opens with puberty — sexual maturation driven by a hormone surge. Primary sex characteristics are the reproductive structures themselves; secondary sex characteristics (facial hair, breast development, deepening voice) signal maturity without being reproductive organs. Menarche is the first menstrual period. Psychologically, the adolescent task is identity formation — testing values, roles, and plans (Erikson's identity vs. role confusion) — while the brain's emotional limbic system runs ahead of a prefrontal cortex that keeps maturing into the mid-twenties.
Physical abilities peak in the twenties and decline gradually, but cognition splits in two. Fluid intelligence — speed and novel problem-solving — tends to decline with age. Crystallized intelligence — vocabulary and accumulated knowledge — holds steady or grows into late life. [GRAPH: two lines plotted against age 20–80; the "crystallized" line rises gradually and plateaus late; the "fluid" line peaks in the mid-20s and declines steadily.] Memory ages selectively too: recall slips more than recognition. Cross-sectional studies historically overstated cognitive decline because of the cohort effect; longitudinal work (e.g., Schaie's Seattle Longitudinal Study) shows a gentler curve.
1. (C) Zygote → embryo → fetus. The fertilized cell (zygote) becomes the organ-forming embryo, then the growing fetus until birth. (A), (B), (D), and (E) each scramble the sequence — the common misconception is that "embryo" names the very first cell, when it actually names the organ-formation period. Fix: Zygote = the cell, embryo = organs form, fetus = grows to birth — Z-E-F, alphabetically last to first is wrong, chronological is Z→E→F.
2. (B) Contact comfort. The monkeys spent nearly all their time on the soft, foodless cloth mother and fled to it when scared — comfort of touch, not calories, built the bond. (A) is the "cupboard theory" Harlow refuted; (C) imprinting is Lorenz's finding in birds, not mammalian attachment; (D) restates the food explanation in behaviorist language — the data contradicted it; (E) both surrogates were equally unrelated, so relatedness explains nothing. Fix: Harlow = attachment comes from contact comfort; "loves whoever feeds them" is the refuted theory.
3. (A) Secure attachment. Distress at separation plus quick soothing and a return to play at reunion is the secure signature. (B) avoidant infants seem indifferent and ignore the returning caregiver; (C) resistant infants cling and angrily resist comfort without settling; (D) disorganized infants show no coherent strategy; (E) stranger anxiety is fear of unfamiliar people — Elena reacts to her mother's departure, not a stranger. Fix: Classify attachment by the REUNION — comforted = secure, ignores = avoidant, clings-and-fights = resistant.
4. (B) Conservation. Believing quantity changed because the container's shape changed is the textbook conservation failure of the preoperational stage. (A) object permanence develops in infancy and concerns hidden objects, not amounts — the classic mix-up; (C) theory of mind concerns others' beliefs, not quantities; (D) attachment is unrelated to this cognitive task; (E) assimilation is how schemas absorb new information, not a quantity concept. Fix: "Taller glass = more juice" = conservation failure (preoperational); hidden object = object permanence (infancy).
5. (A) The cohort effect. In a cross-sectional design the 80-year-olds differ from the 20-year-olds in generation — schooling, nutrition, test familiarity — so "decline" may be generational, not aging. (B) attrition plagues longitudinal designs, the reverse error; (C) placebo effects require a treatment, absent here; (D) experimenter bias isn't the built-in structural flaw of this design; (E) regression toward the mean concerns retesting extreme scorers, and no one was retested. Fix: Cross-sectional flaw = cohort effect; longitudinal flaw = attrition — match the flaw to the design.
6. (D) Conventional. Rosa reasons from law and social order — the conventional level's core. (A) preconventional reasoning cites punishment or self-interest ("he'd go to jail"); (B) postconventional appeals to principles above the law, the opposite direction; (C) "egocentric" is a Piagetian term, not a Kohlberg level; (E) formal operational is a cognitive stage, not moral reasoning. Fix: Punishment/self-interest = preconventional; law-and-order/approval = conventional; principle over law = postconventional — always score the WHY.
7. (A) Identity versus role confusion. Actively trying out careers, groups, and beliefs to answer "who am I?" is Erikson's adolescent conflict. (B) intimacy vs. isolation is the young adult task of committing to another person; (C) industry vs. inferiority is the school-age competence conflict; (D) trust vs. mistrust belongs to infancy; (E) generativity vs. stagnation is the midlife concern with the next generation. Fix: "Who am I?" = identity (adolescence); "Can I commit to another?" = intimacy (young adulthood).
8. (B) Zone of proximal development. Tasks impossible alone but achievable with guidance sit precisely in the ZPD. (A) formal operational is a Piagetian stage, not a task zone; (C) a critical period is a biological window (e.g., imprinting), misapplied here; (D) private speech is a child's self-guiding talk, not a range of tasks; (E) scaffolding is the tutor's support, not the zone the tasks occupy — the classic near-miss. Fix: ZPD = the tasks (can't alone, can with help); scaffolding = the help itself.
9. (E) Authoritative. High warmth plus high demand plus explanation defines authoritative parenting, linked to the best outcomes. (A) authoritarian has the rules but not the warmth or reasons — the near-identical-word trap; (B) permissive has warmth without firm rules; (C) uninvolved lacks both; (D) insecure-resistant is an attachment category, not a parenting style. Fix: Rules + warmth + reasons = authoritative; the authoritarian "autocrat" gives rules without reasons.
10. (D) An agent that crosses the placenta and harms prenatal development. That is the definition — alcohol, viruses, certain drugs, radiation. (A) genetic abnormalities are inherited, not environmental agents; (B) reflexes are normal newborn equipment; (C) pubertal hormones act a decade later; (E) infant nutrition occurs after birth, outside the prenatal window. Fix: Teratogen = outside agent, crossing the placenta, harming development BEFORE birth.
11. (E) Crystallized knowledge stays stable or grows while fluid reasoning declines. This split is the best-supported finding in cognitive aging. (A) decline is not uniform — that is exactly the misconception the fluid/crystallized distinction corrects; (B) reverses the finding (recall declines faster than recognition); (C) reverses fluid intelligence's trajectory; (D) reverses the pair — vocabulary is the durable ability. Fix: Fluid (novel speed) slips; crystallized (stored knowledge) stays — aging trades speed for accumulated expertise.
12. (C) Selective dropout may have left an unusually healthy sample. Attrition is the longitudinal design's built-in bias: 40 years of dropouts can leave hardy, motivated survivors who understate decline. (A) and (B) describe the cohort problem and the cross-sectional design — the other method's issue; (D) is false: tracking individual change is precisely what longitudinal designs do; (E) is false: 40 years spans most of adulthood. Fix: Before trusting a longitudinal result, ask who dropped out — attrition biases the later waves.
1. (C) Zygote → embryo → fetus. The fertilized cell (zygote) becomes the organ-forming embryo, then the growing fetus until birth. (A), (B), (D), and (E) each scramble the sequence — the common misconception is that "embryo" names the very first cell, when it actually names the organ-formation period. Fix: Zygote = the cell, embryo = organs form, fetus = grows to birth — Z-E-F, alphabetically last to first is wrong, chronological is Z→E→F.
2. (B) Contact comfort. The monkeys spent nearly all their time on the soft, foodless cloth mother and fled to it when scared — comfort of touch, not calories, built the bond. (A) is the "cupboard theory" Harlow refuted; (C) imprinting is Lorenz's finding in birds, not mammalian attachment; (D) restates the food explanation in behaviorist language — the data contradicted it; (E) both surrogates were equally unrelated, so relatedness explains nothing. Fix: Harlow = attachment comes from contact comfort; "loves whoever feeds them" is the refuted theory.
3. (A) Secure attachment. Distress at separation plus quick soothing and a return to play at reunion is the secure signature. (B) avoidant infants seem indifferent and ignore the returning caregiver; (C) resistant infants cling and angrily resist comfort without settling; (D) disorganized infants show no coherent strategy; (E) stranger anxiety is fear of unfamiliar people — Elena reacts to her mother's departure, not a stranger. Fix: Classify attachment by the REUNION — comforted = secure, ignores = avoidant, clings-and-fights = resistant.
4. (B) Conservation. Believing quantity changed because the container's shape changed is the textbook conservation failure of the preoperational stage. (A) object permanence develops in infancy and concerns hidden objects, not amounts — the classic mix-up; (C) theory of mind concerns others' beliefs, not quantities; (D) attachment is unrelated to this cognitive task; (E) assimilation is how schemas absorb new information, not a quantity concept. Fix: "Taller glass = more juice" = conservation failure (preoperational); hidden object = object permanence (infancy).
5. (A) The cohort effect. In a cross-sectional design the 80-year-olds differ from the 20-year-olds in generation — schooling, nutrition, test familiarity — so "decline" may be generational, not aging. (B) attrition plagues longitudinal designs, the reverse error; (C) placebo effects require a treatment, absent here; (D) experimenter bias isn't the built-in structural flaw of this design; (E) regression toward the mean concerns retesting extreme scorers, and no one was retested. Fix: Cross-sectional flaw = cohort effect; longitudinal flaw = attrition — match the flaw to the design.
6. (D) Conventional. Rosa reasons from law and social order — the conventional level's core. (A) preconventional reasoning cites punishment or self-interest ("he'd go to jail"); (B) postconventional appeals to principles above the law, the opposite direction; (C) "egocentric" is a Piagetian term, not a Kohlberg level; (E) formal operational is a cognitive stage, not moral reasoning. Fix: Punishment/self-interest = preconventional; law-and-order/approval = conventional; principle over law = postconventional — always score the WHY.
7. (A) Identity versus role confusion. Actively trying out careers, groups, and beliefs to answer "who am I?" is Erikson's adolescent conflict. (B) intimacy vs. isolation is the young adult task of committing to another person; (C) industry vs. inferiority is the school-age competence conflict; (D) trust vs. mistrust belongs to infancy; (E) generativity vs. stagnation is the midlife concern with the next generation. Fix: "Who am I?" = identity (adolescence); "Can I commit to another?" = intimacy (young adulthood).
8. (B) Zone of proximal development. Tasks impossible alone but achievable with guidance sit precisely in the ZPD. (A) formal operational is a Piagetian stage, not a task zone; (C) a critical period is a biological window (e.g., imprinting), misapplied here; (D) private speech is a child's self-guiding talk, not a range of tasks; (E) scaffolding is the tutor's support, not the zone the tasks occupy — the classic near-miss. Fix: ZPD = the tasks (can't alone, can with help); scaffolding = the help itself.
9. (E) Authoritative. High warmth plus high demand plus explanation defines authoritative parenting, linked to the best outcomes. (A) authoritarian has the rules but not the warmth or reasons — the near-identical-word trap; (B) permissive has warmth without firm rules; (C) uninvolved lacks both; (D) insecure-resistant is an attachment category, not a parenting style. Fix: Rules + warmth + reasons = authoritative; the authoritarian "autocrat" gives rules without reasons.
10. (D) An agent that crosses the placenta and harms prenatal development. That is the definition — alcohol, viruses, certain drugs, radiation. (A) genetic abnormalities are inherited, not environmental agents; (B) reflexes are normal newborn equipment; (C) pubertal hormones act a decade later; (E) infant nutrition occurs after birth, outside the prenatal window. Fix: Teratogen = outside agent, crossing the placenta, harming development BEFORE birth.
11. (E) Crystallized knowledge stays stable or grows while fluid reasoning declines. This split is the best-supported finding in cognitive aging. (A) decline is not uniform — that is exactly the misconception the fluid/crystallized distinction corrects; (B) reverses the finding (recall declines faster than recognition); (C) reverses fluid intelligence's trajectory; (D) reverses the pair — vocabulary is the durable ability. Fix: Fluid (novel speed) slips; crystallized (stored knowledge) stays — aging trades speed for accumulated expertise.
12. (C) Selective dropout may have left an unusually healthy sample. Attrition is the longitudinal design's built-in bias: 40 years of dropouts can leave hardy, motivated survivors who understate decline. (A) and (B) describe the cohort problem and the cross-sectional design — the other method's issue; (D) is false: tracking individual change is precisely what longitudinal designs do; (E) is false: 40 years spans most of adulthood. Fix: Before trusting a longitudinal result, ask who dropped out — attrition biases the later waves.