INTRODUCTION

Intelligence tests are about one hundred years old. If you agree with Boring (1923) that intelligence is what the intelligence tests measure, then the science of intelligence is one hundred years old. I will call this psychometrically defined intelligence. Empirically the study of psychometric intelligence is a booming field, for it has led to a very large literature, impressive technological developments, and coherent relationships among test scores (Carroll, 1993). However, it has a weakness.

A purely psychometric approach to intelligence lets the technology of measurement define the concept, rather than the concept defining an appropriate measurement technology. Along with many others, I prefer a more conceptual, less boring approach. The conceptual definition of intelligence as individual variation in mental competence has a longer history. In the sixteenth century the Spanish philosopher Juan Huarte de San Juan (Huarte, 1575/1991) proposed a multifaceted theory of intelligence that was not too far from today's crystallized–fluid distinction. In the nineteenth century, Galton (1883) used laboratory techniques for measuring individual differences in basic mental processes that are recognizable ancestors of paradigms used in today's laboratories. And for that matter, Binet, the founder of modern testing, was not entirely atheoretic (Sternberg, 1990). All interesting theories of intelligence try to go beyond test scores to connect individual differences with a theory of how the mind works. Developing such a theory is the province of cognitive psychology.