Abstract
The article calls for differentiating between three kinds of studies of students' conceptions in science—descriptive studies, explanatory studies, and studies attempting to foster conceptual change. Separate reviews of each of these categories of research are needed due to the different aims and the different theoretical and methodological issues pertaining to each category. Descriptive studies are reviewed in an attempt to illustrate the benefits of such a differentiation. The claims that students hold a limited number of preconceptions about science topics, and that these preconceptions, which sometimes hinder the acquisition of science concepts, often persist after instruction are found to be well supported in the literature. Some theoretical and methodological issues related to descriptive studies are discussed.