1. The science of human development seeks to understand how and why people—all people, everywhere, of every age—change over time, and how and why they remain the same.
2. Development is multidirectional, multicontextual, multicultural, multidisciplinary, and plastic.
3. The science of human development is empirical, meaning that it focuses on data, facts, observation, and experimentation.
4. The scientific method consists of five basic steps: (1) formulate a research question, (2) develop a hypothesis, (3) test the hypothesis, (4) draw conclusions, and (5) make the findings available.
5. Replication of research findings verifies the findings and leads researchers to more definitive and extensive conclusions. In replicating research, scientists use different participants.
6. The nature–nurture debate is the question of how much of any characteristic is the result of genes (nature) and how much is the result of experience (nurture). Genes and environment affect every aspect of development.
7. The fact that nature and nurture interact helps clarify another question: whether or not timing is crucial. Research has shown that there are both critical periods and sensitive periods in development.
8. The value of understanding that nature and nurture interact also can be seen in research on the origins of violence in young people. One study found that mistreated boys were more likely to be overly aggressive if they had a particular variation in the MAOA gene (the low-MAOA gene). However, even if they inherited the gene that produces low levels of the enzyme monoamine oxidase A, boys who had not been mistreated tended to become peaceable adults.
9. The emphasis on the interaction between people and within each person is highlighted by the dynamic-systems theory, which stresses fluctuations and transitions.
II. The Life-Span Perspective
1. The life-span perspective views human development as multidirectional, multicon- textual, multicultural, multidisciplinary, and plastic.
2. Change is apparent in each aspect of life and in every direction. Research shows that some shifts are stagelike and other shifts are gradual.
3. The approach that emphasizes the influence of the systems, or contexts, that support the developing person is Urie Bronfenbrenner’s ecological-systems approach. According to this model, human development is supported by systems at four nested levels: the microsystem (immediate social setting), the exosystem (local, such as school and church), the macrosystem (cultural values, political processes, economic policies, and social conditions), and the chronosystem, which emphasizes the importance of his- torical time on development. A fifth system, the mesosystem, connects systems, for example, the interface between home and school. As a reflection of the impact of biolo- gy on development, Bronfenbrenner renamed his theory bioecological theory.
4. Developmentalists take a broad view of development, recognizing the influence on development of external forces, that is, the context of development. This larger perspective makes it imperative that development be understood in its social context, including its historical and socioeconomic contexts.
5. A cohort is a group of people born within a few years of each other who tend to share certain historical events and cultural shifts.
6. Socioeconomic status (SES) is determined by several overlapping variables, includ- ing income, wealth, education, place of residence, and occupation. Although low income obviously limits a person, other SES factors (such as education) can make poverty better or worse.
7. Culture affects development in a multitude of interrelated ways, from whether to cover your mouth when laughing to what to eat for breakfast.
8. An ethnic group is a collection of people who share certain attributes, such as ancestry, national origin, religion, and language.
9. Although race was once defined