The purpose of this article is to elaborate Cottrill et al.'s (1996) conceptual framework of limit, an explanatory model of how students might come to understand the limit concept. Drawing on a retrospective analysis of 2 teaching experiments, we propose 2 theoretical constructs to account for the students' success in formulating and understanding…

A conservation problem of numerical equivalence which 80% of adults reliably fail and 40% of third graders pass was developed, and responses of 188 subjects (Grades 2, 3, 5, 7, 9, 11 and college) to it and related number conservation and probability problems indicated that the differences in nonconservation were rooted in subjects' different…

This paper reports two studies that examined changes in the participants' level of moral reasoning after exposure to the Kohlberg cognitive-developmental intervention model (1975). This approach focuses on universal moral principles which are manifested in a series of developmental stages. Knowledge of these stages provides one with an outline for…