Abstract
In this chapter we review the approach-avoidance process theory of personality proposed by Jeffrey Alan Gray (1970, 1973), now widely known as reinforcement sensitivity theory (RST). We begin by placing RST in the broader context of theory and research concerning approach and avoidance motivation. We then provide a snapshot of the animal research upon which the brain-behavior systems of RST were based. Next we discuss the vexed issue of how these systems might manifest themselves in personality space, and we review the latest empirical tests of RST as an explanation of personality variation. Finally, we consider applications of RST beyond personality: specifically, we review current opinion on the relevance of RST to psychopathology and clinical dysfunction and the potential for RST to underlie achievement motivation in learning and performance contexts. We conclude by looking to the future and highlighting a major challenge that we believe RST now faces.