Jeffrey Alan Gray was known for his important contributions to many areas of psychology, latterly in his career, schizophrenia, stem-cell transplantation and a full-blown theory of the functions of consciousness. But his theory of anxiety and personality more generally – now known as Reinforcement Sensitivity Theory (RST) – is one of his greatest achievements and secures his place in the history books.

The high regard in which Jeffrey is held by colleagues world-wide was evident in the fact that all the authors I approached to contribute to this book readily agreed. I am grateful to them all for their scholarly chapters. I am especially grateful to William Revelle for agreeing to read all chapters before giving his reflections on the position of RST in the wider field of personality psychology. The contributors have given us much to consider, and in their work we may discern many of the landmarks that will surely characterize RST in the decades to follow.

This book testifies to the important developments that have taken place in Jeffrey's thinking over the years, as well as the thinking of others inspired by his ground-clearing work. As show-cased in this book, ‘Gray's theory’ is not a fossilized set of principles, assumptions and contentions; rather, it is a fecund scientific perspective that opens up new research possibilities. We witness this fecundity in the vitality and variety of theories and approaches that characterize RST research today, as well as in the variegated shoots of related reinforcement-based theories of motivation, emotion and personality.