This paper discusses research on how concepts differ in their internal organization and how these differences interact with and affect cognitive processing in children. Two types of natural concepts are focused on: classes (nouns with class-inclusion organization, such as "trees,""students,""soldiers" and collections (nouns with part-whole structures, such as "forest,""army,""class,""team"). Collections are said to have a greater psychological integrity and to be easier to conceive as an aggregate or organized totality than classes. To test the psychological reality and implications of this distinction, several tasks that require treating objects as organized into aggregates rather than as individuals were given to children. Children's ability to answer the Piagetian class inclusion problem was considerably improved when the question was phrased in terms of collection rather than class labels. Similarly, children's performance on the number conservation problem was improved when the objects were described as collections rather than classes. Collection labels allowed children to use the cardinality principle on a number problem which they otherwise would have failed. These results indicate a relation between how children organized or represent information and their subsequent ability to operate on that representation. The problem on these tasks is that children do not have the ability to impose the appropriate organization, not that they need to be taught new skills. Details of the research are not provided. (Author/SS)