This article has evolved through a few stages. It began as a talk that I gave at George
Andrews’s birthday conference at Penn State in the autumn of 1998. Its theme then was
that although there appear to be some studies in the literature of mathematics education
that support the ideas of cognitive-based teaching and learning of mathematics, in fact
these studies are seriously flawed in their methodology, or else lacking in proved
conclusions, so that in the final analysis there are not any studies that demonstrate the
effectiveness of such instruction.