First Published in 1974. This volume is a collection of the papers presented at the Ninth Annual Symposium on Cognition, held at Carnegie-Mellon University in May 1973. The subject of the symposium was knowledge, or rather its internal representation in human memory, or in computer systems. Of all the recent symposia in this series, this one represents a meeting of the minds, in that all of the participants were strongly oriented toward information processing theories of cognition.