ABSTRACT. Leron and Hazzan show how some recent developments in cognitive psychology can help interpret empirical results from mathematics education. English states that students need to learn mathematics with understanding by actively building new knowledge from existing knowledge and experience. Bergeson et al. argue that students learning multiplication as a conceptual operation need exposure to a variety of models. Delbeke asserts that students with good conceptual understanding are able to perform successfully on near-transfer tasks and to develop procedures and skills they have not been taught. As Sigman puts it, formal ideas in mathematics reflect the workings of the brain like a massive collective cognitive experiment: mathematics is biology.