Читать книгу Infants and Children in Context - Tara L. Kuther - Страница 76

A cross-sectional research study compares groups of children of different ages at a single point in time. For example, to examine how vocabulary improves in elementary school, a researcher might measure the vocabulary size of children in first, third, fifth, and seventh grades. The resulting comparison describes how the vocabulary of first-grade children differs from older children in Grades 3, 5, and 7. However, the results do not tell us whether the observed age differences in vocabulary reflect age-related or developmental change. In other words, we don’t know whether the first graders will show the same pattern of vocabulary ability and use as the seventh graders, 6 years from now, when they are in seventh grade.

Cross-sectional research permits age comparisons, but participants differ not only in age but also in cohort, limiting the conclusions researchers can draw about development. A cohort is a group of people of the same age who are exposed to similar historical events and cultural and societal influences. Although the first-grade and seventh-grade children may attend the same school, they are different ages and different cohorts and thus may have different experiences. For example, suppose the elementary school changed the language curriculum, leading the first-grade children to be taught a new, improved curriculum, whereas the seventh graders received the old curriculum. The first graders and seventh graders therefore have different experiences because they were taught different curricula. Any differences in vocabulary may be due to age but also to different experiences. Therefore, cross-sectional research is an important source of information about age differences (how the first graders differ from seventh graders), but it cannot provide information about age change (whether the first graders will show similar development as the seventh graders).