This book develops a theory of style from a cognitive psychology approach. Notions of style were explored from the point of view of design processes, with a focus on how a style of design, especially an individual style, emerges. Special attention was given to the psychological mechanisms that cause the formation of a style. An operational definition, the degree to which a style could have been recognized, and the measurement of a unique style were fully developed in order to create a fundamental theory of style, justified through psychological experiment. The concepts from this book are broadly applicable to readers from the fields of design and design professions, providing insight towards the improvement and strengthening of their own design style.