Guidepost 1: What purposes do theories serve?

• A theory is used to explain data and generate hypotheses that can be tested by research.

Guidepost 2: What are three basic theoretical issues on which developmental scientists differ?

• Developmental theories differ on three basic issues: the relative importance of heredity and environment, the active or passive character of development, and the existence of stages of development.
• Some theorists subscribe to a mechanistic model of development; others to an organismic model.

Guidepost 3: What are five theoretical perspectives on human development, and what are some theories representative of each?

• The psychoanalytic perspective sees development as motivated by unconscious emotional drives or conflicts. Leading examples are Freud's and Erikson's theories.
• The learning perspective views development as a result of learning based on experience. Leading examples are Watson's and Skinner's behaviorism and Bandura's social learning theory.
• The cognitive perspective is concerned with thought processes. Leading examples are Piaget's cognitive-stage theory, the information-processing approach, and the cognitive neuroscience approach.
• The evolutionary/sociobiological perspective, represented by E. O. Wilson, focuses on the adaptiveness, or survival value, of behavior. It includes a number of disciplines, such as ethology and evolutionary psychology. Developmental evolutionary psychologists seek to identify behaviors that are adaptive at particular ages.
• The contextual perspective focuses on interaction between the individual and the social context. Leading examples are Bronfenbrenner's and Vygotsky's theories.

Guidepost 4: How do developmental scientists study people, and what are some advantages and disadvantages of each research method?

• Research can be either quantitative or qualitative, or both.
• To arrive at sound conclusions, quantitative researchers use the scientific method.
• Random selection of a research sample can ensure generalizability.
• Three forms of data collection are self-reports (diaries, interviews, and questionnaires); behavioral and performance measures; and observation.
• Two basic qualitative designs used in developmental research are the case study and the ethnographic study. Cross-cultural research can indicate whether certain aspects of development are universal or culturally influenced.
• Two quantitative designs are the correlational study and experiment. Only experiments can firmly establish causal relationships.
• Experiments must be rigorously controlled so as to be valid and replicable. Random assignment of participants can ensure validity.
• Laboratory experiments are easiest to control and replicate, but findings of field experiments may be more generalizable beyond the study situation. Natural experiments may be useful in situations in which true experiments would be impractical or unethical.
• The two most common designs used to study age-related development are longitudinal and cross-sectional. Cross-sectional studies compare age groups; longitudinal studies describe continuity or change in the same participants. The sequential study is intended to overcome the weaknesses of the other two designs.
• A microgenetic study allows direct observation of change over a short period of time.

Guidepost 5: What ethical problems may arise in research on humans?

• Ethical issues in research include the rights of participants to informed consent, avoidance of deception, protection from harm and loss of dignity, and guarantees of privacy and confidentiality.