Reinforcement sensitivity theory (RST) proposes three brain-behavioral systems that underlie individual differences in sensitivity to reward, punishment, and motivation. While not originally defined as a theory of personality, the RST has been used to study and predict anxiety, impulsivity, and extraversion. The theory evolved from Gray's biopsychological theory of personality to incorporate findings from a number of areas in psychology and neuroscience, culminating in a major revision in 2000.Gray, J.A. and McNaughton, N., The Neuropsychology of Anxiety: An Enquiry into the Functions of the Septo-Hippocampal System, July 2003, (Oxford: Oxford University Press), and The revised theory distinguishes between fear and anxiety and proposes functionally related subsystems. Measures of RST have not been widely adapted to reflect the revised theory due to disagreement over related versus independent subsystems. Despite this controversy, RST informed the study of anxiety disorders in clinical settings and continues to be used today to study and predict work performance. RST, built upon Gray's behavioral inhibition system (BIS) and behavioral activation system (BAS) understanding, also may help to suggest predispositions to and predict alcohol and drug abuse. RST, a continuously evolving paradigm, is the subject of multiple areas of contemporary psychological enquiry.Corr, P.J., The Reinforcement Sensitivity Theory of Personality, April 2008, (Cambridge: Cambridge University),
Origins and evolution of the theory Gray's biopsychological theory of personality was informed by his earlier studies with Mowrer on reward, punishment, and motivation and Hans Eysenck's study of the biology of personality traits. Eysenck linked Extraversion to activation of the ascending reticular activating system, an area of the brain which regulates sleep and arousal transitions.
Eysenck's two original personality factors, Neuroticism and Extraversion, were derived from the same lexical paradigm used by other researchers (e.g., Gordon Allport, Raymond Cattell) to delineate the structure of personality. Eysenck's Extraversion-Arousal Hypothesis states that under low stimulation conditions, introverts (defined as low in Extraversion) will be more highly aroused than extraverts; however, under high stimulation, introverts may become over-aroused, which will feedback within the ascending reticular activating system and result in decreases in arousal. In contrast, extraverts tend to show greater increases in arousal under high stimulation. Eysenck also studied the relationship between neuroticism and activation of the limbic system using classical emotional conditioning models. His theory focused more on anxiety as a disorder than a personality trait. Eysenck's theory predicts that introverts are more likely to develop anxiety disorders because they show higher neuroticism and stronger emotional conditioning responses under high arousal. His theory was criticized because introverts often show the opposite pattern, weaker classical conditioning under high arousal, and some supporting data confounded personality traits with time of day.
Gray's biopsychological theory: behavioral activation and inhibition systems Unlike Eysenck, Gray believed that personality traits and disorders could not be explained by classical conditioning alone. Gray proposed the Biopsychological Theory of personality in 1970 based on extensive animal research.Larsen, R. J., & Buss, D. M. (2009). Personality Psychology: Domains of Knowledge about Human Nature. New York, NY: McGraw-Hill. His theory emphasized the relationship between personality and sensitivity to reinforcement (i.e. reward and punishment). Eysenck's theory emphasized Extraversion, Neuroticism, and arousal, while Gray's theory emphasized Impulsivity, Anxiety, approach motivation, and avoidance motivation.
In his original theory, Gray proposed two new dimensions to Eysenck's theory - anxiety and impulsivity. Gray's anxiety, or BIS, correlates with Eysenck's neuroticism. Gray's impulsivity, or BAS, correlates with Eysenck's extraversion. Even though Gray's original theory was modified later by Gray himself, the original theory still made some contributions to the study of biological systems and their role in personality. The largest of these contributions was that the biological central nervous system can be linked to a psychological reward system, composed of approach and inhibition systems.
Gray's model of personality was based on three hypothesized brain systems:
Behavioral activation system (BAS) The BAS includes brain regions involved in regulating arousal: cerebral cortex, thalamus, and striatum.De Pascalis, V., Fiore, A., Sparita, A. (1996). Personality, event-related potential (ERP) and heart rate (HR): An investigation of Gray's theory. Personality and Individual Differences, 20, 733-746. The system is responsive to conditioned and unconditioned reward cues. BAS regulates approach behaviors and is referred to as the reward system. It has also been called the "go" system because it motivates actions that lead to rewards. In general, individuals with a more active BAS tend to be more impulsive and may have difficulty inhibiting their behavior when approaching a goal.Gray, J. A. (1991). The neurophysiology of temperament. In J. Strelau & A. Angleitner (Eds.), Explorations in temperament: International perspectives on theory and measurement (pp. 105-128). New York, NY: Plenum. Furthermore, BAS is related to stimuli associated with the presence of reward and/or the cease of punishment, also understood as positive reinforcement.
Behavioral inhibition system (BIS) The BIS also includes brain regions involved in regulating arousal: the brain stem, and neocortical projections to the frontal lobe. BIS is responsive to punishment, novelty, uncertainty, and non-rewarding stimuli. BIS regulates avoidance behaviors and is often referred to as the punishment system. It has also been called the "stop" because it encourages inhibition of behaviors. Individuals with more active BIS may be vulnerable to negative emotions, including frustration, anxiety, fear, and sadness. Furthermore, BIS is related to stimuli associated with the presence of punishment and/or the cease of reward, also understood as negative reinforcement.
Fight/flight system (FFS) The FFS encourages extreme reactions in response to threats. These include reactions of rage, panic, and fight or flight, and is sensitive to unconditioned aversive stimuli. FFS is often referred to as the threat system. A common misunderstanding can be that FFS is a measure of one's reaction to lean more towards fighting or to lean more towards fleeing in response to perceived threats; however, FFS is a measure of one's intensity to respond with either fight or flight behavior, as opposed to reacting not so acutely to perceived threats. Individuals with more sensitive FFS are quicker to fight or flee in dangerous situations.
According to Gray, personality traits are associated with individual differences in the strengths of BAS (approach motivation) and BIS (avoidance motivation) systems. As it is defined for the remainder of the article, higher BAS/BIS refers to greater activation of that system.Zelenski, J. M., & Larsen, J. R. (1999). Susceptibility to affect: A comparison of three personality taxonomies. Journal of Personality, 67, 761-791.
Measures High BAS is generally associated with high extraversion, low neuroticism, and trait impulsivity, while high BIS is associated with low extraversion, high neuroticism, and trait anxiety. In addition to predicting trait standings, high BAS is associated with higher positive affect in response to reward, while high BIS is associated with higher negative affect in response to punishment. Studies in Gray's laboratory supported his prediction that extraverts, higher in BAS and lower in BIS than introverts, are more sensitive to rewards, experience higher levels of positive affect, and learn faster under rewarding conditions.
The most widely used measures of the approach (BAS) and avoidance (BIS) systems are the BIS/BAS scales developed by Carver and White in 1994. The Generalized Reward and Punishment Expectancies Scales (GRAPES) were also used to operationalize BIS and BAS. Both self-report measures (listed above) and behavioral measures (such as affective modulation of the eyeblink startle response) have been used to test predictions and provide mixed support for Gray's theory.
Critique These measures were constructed under the assumption that BIS, BAS and associated traits Anxiety and Impulsivity are independent. In contrast, Gray first described BIS and BAS as opposing systems with bidirectional inhibitory links in animal models. Thus, empirical results that claimed to falsify the theory may have relied on faulty predictions for independent, non-interacting systems. Gray's theory was also criticized because the boundary between FFS (threat response system) and BIS (punishment system) was difficult to define empirically, akin to differentiating between fear and anxiety. Matthews and Gilliland proposed separate cognitive systems underlying fear and anxiety and emphasized the need to study these systems outside of animal models. These critiques led to a major revision and renaming of the theory in 2000. The Reinforcement Sensitivity Theory (RST) redefined the three systems underlying anxiety, impulsivity, motivation, and reinforcement learning.
Reinforcement sensitivity theory Reinforcement sensitivity theory is one of the major biological models of individual differences in emotion, motivation, and learning. The theory distinguishes between fear and anxiety, and links reinforcement processes to personality.
Behavioral activation system (BAS) Proposed to facilitate reactions to all appetitive/rewarding stimuli and regulates approach behavior.
Behavioral inhibition system (BIS) Proposed to mediate conflict both within and between FFFS and BAS: FFFS (avoidance) and BAS (approach) (or BAS-BAS, FFFS-FFFS). These conflicts underlie anxiety.
Fight-flight-freeze system (FFFS) Proposed to mediate reactions to all aversive/ punishing stimuli (conditioned and unconditioned), regulates avoidance behavior, and underlies fear.
Improved measures The fight-flight-freeze system (FFFS) was expanded to include all aversive/punishment stimuli, conditioned and unconditioned. Similarly, the Behavioral Activation System (BAS) was expanded to include all appetitive/reward stimuli. The Behavioral Inhibition System (BIS) was defined as a conflict system activated whenever both BAS and FFFS are activated together or multiple inputs compete within the systems, thereby producing anxiety. If the systems are assumed to be functionally related, the effect of a given stimulus is dependent upon the strength of that stimulus, reactivity in the activated system, and strength of the competing system. Thus, for a reward, the behavior output from BAS is dependent on the strength of the reward, activation of the BAS, and inhibition strength of BIS. For example, if a reward outweighs a threat, the BIS should excite the BAS and inhibit the FFFS, which will likely result in approach behavior.