Gray's biopsychological theory of personality

Gray's biopsychological theory of personality is a model of the general biological processes relevant for human psychology, behavior, and personality, proposed by research psychologist Jeffrey Alan Gray in 1970. The theory is well-supported by subsequent research and has general acceptance among professionals.

Gray hypothesized the existence of three brain-based systems for controlling a person's interactions with their environment: the behavioural inhibition system (BIS) and the behavioural activation system (BAS), and the fight, flight, or freezing system (FFFS). BIS is related to sensitivity to punishment and avoidance motivation. BAS is associated with sensitivity to reward and approach motivation. FFFS is associated with sensitivity to fear and how an individual responds to it. There is evidence that the Behavioral Inhibition and Behavioral Activations system are connected to mood control, with positive or negative emotions occurring when rewarded or punished. Those with a relatively high BAS are said to be extroverted and outgoing while those with a high BIS tend to be more reserved and introverted. Psychological scales have been designed to measure these hypothesized systems and study individual differences in personality. Neuroticism, a widely studied personality dimension related to emotional functioning, is positively correlated with BIS scales and negatively correlated with BAS scales.

The biopsychological theory of personality is similar to another one of Gray's theories, reinforcement sensitivity theory. The original version of Gray's reinforcement sensitivity theory of personality was developed in 1976 and Gray revised it independently in 1982. Then in 2000 further and more thorough revisions were made alongside McNaughton. The purpose of the revision was to adapt the theory according to new inputs of scientific findings since the 1980s. Reinforcement sensitivity theory arose from the biopsychological theory of personality. The Biopsychological Theory of Personality was created in 1970 after Gray disagreed with Hans Eysenck's arousal theory that dealt with biological personality traits. According to Eysenck, differences in extraversion are a result of differences in sensitivity of the ascending reticular activating system. People with less sensitive systems are not easily aroused and seek additional stimulation, resulting in an extraverted personality. People with more sensitive systems are overstimulated and try to avoid additional stimulation, resulting in an introverted personality. People with a sensitivity dependent system will engage fight, flight, or freezing (FFFS) depending on the amount and type of stimuli present. They will tend to deal with the amount of stimuli present (fight) or avoid the stimuli (flight), resulting in a more tolerant introverted personality. Individuals may also not react to the stimuli, in which case they freeze.

The development of the biopsychological theory of personality occurred during Gray's time at Oxford where he was a fellow and lecturer.

Gray's main critique of Eysenck's theory was that introverts are not more sensitive to conditioning, but are more responsive to non reward and punishment. The evidence Gray collected for his hypothesis on the biological basis of personality comes from blink tests done on humans and studies done on animals injected with sodium amobarbital. Using animal subjects allows researchers to test whether different areas of the brain are responsible for different learning mechanisms. Specifically, Gray's theory concentrated on understanding how reward or punishment related to anxiety and impulsivity measures. His research and further studies have found that reward and punishment are under the control of separate systems and as a result people can have different sensitivities to such rewarding or punishing stimuli.

The behavioral inhibition system (BIS), as proposed by Gray, is a neuropsychological system that predicts an individual's response to anxiety-relevant cues in a given environment. This system is activated in times of punishment, boring things, or negative events. By responding to cues such as negative stimuli or events that involve punishment or frustration, this system ultimately results in avoidance of such negative and unpleasant events. According to Gray's Theory, the BIS is related to sensitivity to punishment as well as avoidance motivation. It has also been proposed that the BIS is the causal basis of anxiety. High activity of the BIS means a heightened sensitivity to nonreward, punishment, and novel experience. This higher level of sensitivity to these cues results in a natural avoidance of such environments in order to prevent negative experiences such as fear, anxiety, frustration, and sadness. People who are highly sensitive to punishment perceive punishments as more aversive and are more likely to be distracted by punishments.

The physiological mechanism behind the BIS is believed to be the septohippocampal system and its monoaminergic afferents from the brainstem. Using a voxel-based morphometry analysis, the volume of the regions mentioned was assessed to view individual differences. Findings may suggest a correlation between the volume and anxiety-related personality traits. Results were found in the orbitofrontal cortex, the precuneus, the amygdala, and the prefrontal cortex.

The behavioral activation system (BAS), in contrast to the BIS, is based on a model of appetitive motivation - in this case, an individual's natural disposition to pursue and achieve goals. The BAS is aroused when it receives cues corresponding to rewards and controls actions that are not related to punishment, rather actions regulating approachment type behaviors. This system has an association with hope. According to Gray's theory, the BAS is sensitive to conditioned appealing stimuli, and is associated with impulsivity. It is also thought to be related to sensitivity to reward as well as approach motivation. The BAS is sensitive to nonpunishment and reward. Individuals with a highly active BAS show higher levels of positive emotions such as elation, happiness, and hope in response to environmental cues consistent with nonpunishment and reward, along with goal-achievement. In terms of personality, these individuals are also more likely to engage in goal-directed efforts and experience these positive emotions when exposed to impending reward. BAS is considered to include trait impulsivity that is also related to psychopathological disorders such as ADHD, substance use disorder, and alcohol use disorder. The higher the BAS score, or the higher the impulsive, the more it is likely to be related to psycho-pathological or dis-inhibitory disorders. Certain aspects of the dopaminergic reward system activate when reward cues and reinforcers are presented, including biological rewards such as food and sex. These brain areas, which were highlighted during multiple fMRI studies, are the same areas associated with BAS. The BAS is believed to play a role in romantic love.