The Reinforcement Sensitivity Theory is a theory of personality that proposes that there are 3 systems in the brain regulating that underlie individual differences in sensitivity to reward, punishment, and motivation. Proposed in the 1970s by the British psychologist Jeffrey Alan Gray, the theory was not initially envisioned as a theory of personality. However, in the years since, it has been widely used as such. The systems in the brain proposed by this theory are the behavioral activation system (or BAS, describing how easily one is motivated by rewards), the behavioral inhibition system (or BIS, describing how strongly one responds to punishment or anticipation of punishment, roughly corresponding to trait anxiety), and the fight-flight-freeze system (or FFFS, describing how strongly a person reacts to threats)