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A cross-sequential research study combines the best features of cross-sectional and longitudinal research by assessing multiple cohorts over time, enabling scientists to make comparisons that disentangle the effects of cohort and age (see Table 1.5). Consider the vocabulary study of children in Grades 1 through 7 once more. A cross-sequential design would begin by measuring vocabulary in first-, third-, fifth-, and seventh-grade children. The children are followed up 2 years later: the first graders are in third grade, the third graders are now in fifth grade, and the fifth graders are in seventh grade (assume the seventh graders graduated elementary school and have left the study). A new group of first-grade children are introduced to the study. Two years later, the first graders are in third grade, the third graders are in fifth grade, the fifth graders are in seventh grade, the seventh graders have aged out of the study, a new group of first-grade children are introduced to the study, and so on (Figure 1.6).

Description

Figure 1.6 Cross-Sequential Research Design

The cross-sequential design provides information about age, cohort, and age-related change. The cross-sectional data (comparisons of first through seventh graders during a given year) permit comparisons across age-groups. But, as we have seen, these cross-sectional comparisons may reflect cohort effects rather than developmental differences. The longitudinal data (annual follow-up of participants in Grades 1 through 7) allow researchers to examine age-changes; that is, how the group of first graders develop throughout elementary school. However, studying only one cohort can also be misleading. A cross-sequential design helps developmental scientists separate cohort effects from age-related change. Because several cohorts are examined at once and over time, researchers can determine the effect of cohort. The sequential design is complex, but it permits developmental scientists to effectively answer questions about development.

Table 1.5

In summary, scientists use the scientific method to systematically ask and seek answers to questions about human development. Researchers’ decisions about measures and research designs influence the information that they collect and the conclusions that they make about development. Researchers have responsibilities to conduct sound research and also to adhere to standards of ethical conduct in research, as the next section describes. See Table 1.5 for a comparison of research designs.