This book discusses the implications of new information technologies and cognitive psychology for mathematical problem solving research and practice.Based on a NATO Advanced Research Workshop held in Portugal in 1991, it offers both empirical research and theoretical papers. The book includes a thorough discussion on the nature and purpose of problem solving as a mathematical activity, providing a view of the importance of complementary activities such as investigations, conjecturing and problem posing. It focuses on cognitive processes, instruction, classroom processes, and the teacher's role, and contains new assessment and teacher education proposals. At a time of important reform movements, when emphasis is put on the role of new information technologies, the book provides an up-to-date view of the developmental work being done on computerized learning environments in the discipline of mathematics, as well as on the efforts to introduce them in educational practice.