Developmental psychology studies how people change physically, cognitively, socially, and emotionally across the lifespan. This cheat sheet helps students compare major stage theories and identify the age ranges, conflicts, and outcomes linked to each theory. It is useful for reviewing AP Psychology, introductory psychology, and human development units.
The focus is on recognizing patterns, applying theories to examples, and avoiding confusion between similar models.
The most important frameworks include Piaget’s cognitive stages, Erikson’s psychosocial conflicts, Kohlberg’s moral reasoning levels, attachment styles, and parenting styles. Piaget explains how thinking changes, Erikson explains social and identity conflicts, and Kohlberg explains moral judgment. Attachment theory emphasizes early caregiver bonds, while parenting style research compares warmth and control.
Development is best understood as the interaction of biology, environment, culture, and individual experience.
Key Facts
- Piaget’s cognitive stages follow the sequence sensorimotor 0-2, preoperational 2-7, concrete operational 7-11, and formal operational 12 and older.
- Piaget’s rule summary is assimilation means fitting new information into an existing schema, while accommodation means changing a schema to fit new information.
- Erikson’s first five psychosocial stages are trust vs. mistrust 0-1, autonomy vs. shame 1-3, initiative vs. guilt 3-6, industry vs. inferiority 6-12, and identity vs. role confusion adolescence.
- Erikson’s later stages are intimacy vs. isolation young adulthood, generativity vs. stagnation middle adulthood, and integrity vs. despair late adulthood.
- Kohlberg’s moral reasoning levels are preconventional with self-interest, conventional with social approval and law, and postconventional with abstract principles.
- Attachment styles are often summarized as secure, anxious-ambivalent, avoidant, and disorganized, based on caregiver responsiveness and the child’s reaction to separation and reunion.
- Baumrind’s parenting style matrix uses warmth and control: authoritative is high warmth and high control, authoritarian is low warmth and high control, permissive is high warmth and low control, and neglectful is low warmth and low control.
- Nature and nurture interact, so development = genes plus environment plus timing plus culture, not genes alone or environment alone.
Vocabulary
- Schema
- A mental framework used to organize and interpret information.
- Object permanence
- The understanding that objects continue to exist even when they cannot be seen, heard, or touched.
- Conservation
- The understanding that quantity stays the same even when shape or appearance changes.
- Attachment
- A close emotional bond between a child and caregiver that affects feelings of safety and later relationships.
- Identity formation
- The process of developing a stable sense of self, values, goals, and social roles.
- Critical period
- A limited developmental window when certain experiences are especially important for normal development.
Common Mistakes to Avoid
- Confusing Piaget with Erikson is wrong because Piaget focuses on cognitive thinking stages, while Erikson focuses on social and emotional conflicts.
- Assuming all children reach stages at the exact same age is wrong because stage ages are approximate and development varies across individuals and cultures.
- Calling authoritarian and authoritative parenting the same is wrong because authoritarian parenting is strict with low warmth, while authoritative parenting combines firm rules with high warmth.
- Treating Kohlberg’s stages as rules for good behavior is wrong because the theory measures moral reasoning, not whether a person’s action is morally correct.
- Explaining development as only nature or only nurture is wrong because most traits and behaviors reflect interaction between genes, environment, timing, and culture.
Practice Questions
- 1 A 4-year-old believes the amount of juice changes when it is poured into a taller glass. Which Piaget stage is most likely, and what concept has the child not mastered?
- 2 A 15-year-old is mainly focused on forming personal values, beliefs, and future goals. Which Erikson stage best fits this example?
- 3 In a classroom of 32 students, 20 give a moral explanation based on obeying rules and gaining approval. What fraction of the class is showing conventional moral reasoning, and what is the percentage?
- 4 A child cries when the caregiver leaves but is quickly comforted when the caregiver returns. Which attachment style is most likely, and what evidence supports that conclusion?
Understanding Developmental Psychology Theories and Stages
Stage theories are useful maps, but they are not fixed schedules that every person follows exactly. A child may show advanced reasoning in one familiar area while needing concrete examples in another. Piaget's tasks often depend on language, attention, school experience, and whether the child understands the instructions.
Young children can sometimes succeed when a problem is made simpler or connected to something they know. Formal reasoning develops unevenly too. A teenager may debate fairness in a social issue but make impulsive choices when emotions are strong.
This does not make the theory useless. It teaches students to look at the kind of thinking a task requires, rather than treating age as a guarantee of ability.
Schemas are mental categories that help people organize experience. They explain why learning can feel easy at times and confusing at others. When new information fits an old schema, assimilation is possible.
When it does not fit, accommodation requires more effort because the person must revise a belief. A student who thinks all scientists work alone in laboratories may need to change that schema after learning about research teams. This process appears in everyday learning, including reading, friendships, and studying science.
Pay attention to examples where a person makes an error first. Errors can reveal the schema they were using before they received new evidence.
Erikson and Kohlberg focus on the meaning people give to social situations. Erikson's conflicts are not tests that are passed once and finished forever. Identity concerns can return during a career change, a move, or a major loss.
Likewise, moral reasoning is different from moral behavior. Someone may explain a high-level principle of justice yet still break a rule because of pressure from friends, fear, or personal benefit. Kohlberg also focused heavily on justice reasoning, while many real moral choices involve care, loyalty, responsibility, and culture.
In class examples, identify the reason for a choice. The action alone does not show the level of moral reasoning.
Attachment research examines patterns of seeking comfort and managing stress with caregivers. These patterns can influence later expectations in close relationships, but they are not permanent labels or predictions of a person's future. Responsive care can support security, while family stress, illness, poverty, conflict, or changes in caregivers can affect behavior.
Parenting styles work in a similar way. Warmth and rules matter, yet the same parenting behavior can have different meanings across cultures and family circumstances. Genes can influence temperament, which can affect how adults respond to a child.
Development is therefore a two-way process. Children shape their environments while environments shape children. When evaluating any theory, notice what it explains well, what evidence supports it, and what human differences it may leave out.