What is Gray’s Biopsychological Theory of Personality?


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

Gray hypothesized the existence of two brain-based systems for controlling a person’s interactions with their environment: the behavioural inhibition system (BIS) and the behavioural activation system (BAS). BIS is related to sensitivity to punishment and avoidance motivation. BAS is associated with sensitivity to reward and approach motivation. 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.

Brief History

The biopsychological theory of personality is similar to another one of Gray’s theories, reinforcement sensitivity theory. The Biopsychological Theory of Personality was created after Gray disagreed with Hans Eysenck’s arousal theory that dealt with biological personality traits. Eysenck looked at the ascending reticular activating system (ARAS) for answering questions about personality. The ARAS is part of the brain structure and has been proposed to deal with cortical arousal, hence the term arousal theory. Eysenck compared levels of arousal to a scale of introversion versus extraversion. The comparison of these two scales was then used to describe individual personalities and their corresponding behavioural patterns. Gray disagreed with Eysenck’s theory because Gray believed that things such as personality traits could not be explained by just classical conditioning. Instead, Gray developed his theory which is based more heavily on physiological responses than Eysenck’s theory.

Gray had a lot of support for his theories and experimented with animals to test his hypotheses. 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.

Behavioural Inhibition System

The behavioural 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 non-reward, 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.

Behavioural Activation System

The behavioural activation system (BAS), in contrast to the BIS, is based on a model of appetitive motivation – in this case, an individual’s 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 behaviours. 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 non-punishment 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 non-punishment 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. The physiological mechanism for BAS is not known as well as BIS, but is believed to be related to catecholaminergic and dopaminergic pathways in the brain. Dopamine is a neurotransmitter commonly linked with positive emotions, which could explain the susceptibility to elation and happiness upon achieving goals which has been observed. People with a highly active BAS have been shown to learn better by reward than by punishment, inverse to BIS as mentioned above. 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.

Compare and Contrast

Together, the two systems work in an inverse relationship. In other words, when a specific situation occurs, an organism can approach the situation with one of the two systems. The systems will not be stimulated at the same time and which system is dominant depends on the situation in terms of punishment versus reward. This phenomenon of the differentiation between the two systems is thought to occur because of the distinct areas in the brain that becomes activated in response to different stimuli. This difference was noted years ago through electrical stimulation of the brain.

The behavioural activation system and behavioural inhibition system differ in their physiological pathways in the brain. The inhibition system has been shown to be linked to the septo-hippocampal system which appears to have a close correlation to a serotonergic pathway, with similarities in their innervations and stress responses. On the other hand, the activation, or reward system, is thought to be associated more with a mesolimbic dopaminergic system as opposed to the serotonergic system.

The two systems proposed by Gray differ in their motivations and physiological responses. Gray also proposed that individuals can vary widely in their responsiveness of the behavioural inhibition system and the behavioural activation system. It has been found that someone who is sensitive to their BIS will be more receptive to the negative cues as compared to someone who is sensitive to their BAS and therefore responds more to cues in the environment that relate to that system, specifically positive or rewarding cues. Researchers besides Gray have shown interest in this theory and have created questionnaires that measure BIS and BAS sensitivity. Carver and White have been the primary researchers responsible for the questionnaire. Carver and White created a scale that has been shown to validly measure levels of individual scores of BIS and BAS. This measure focuses on the differences in incentive motivations and aversive motivations. As previously mentioned these motivations correlate to impulsivity and anxiety respectively.


Since the development of the BAS and BIS, tests have been created to see how individuals rate in each area. The questionnaire is called the Behavioural Inhibition System and Behavioural Activation System Questionnaire.

People can be tested based on their activation of either systems by using an EEG. These tests will conclude whether a person has a more active BIS or BAS. The two systems are independent of each other.

These tests can determine different things about a person’s personality. They can determine if a person has more positive or negative moods. Using psychological test scales designed to correlate with the attributes of these hypothesized systems, neuroticism has been found to be positively correlated with the BIS scale, and negatively correlated with the BAS scale.

According to Richard Depue’s BAS dysregulation theory of bipolar disorders, now doctors and other professionals can determine if a person with bipolar disorder is on the brink of a manic or depressive episode based on how they rate on a scale of BAS and BIS sensitivity. Essentially, this dysregulation theory proposes that people with BAS dysregulation have an extraordinarily sensitive behavioural activation system and their BAS is hyper-responsive to behavioural approach system cues. If a person with bipolar disorder self-reports high sensitivity to BAS, it means that a manic episode could occur faster. Also, if a person with bipolar disorder reports high sensitivity to BIS it could indicate a depressive phase. A better understanding of BAS dysregulation theory can inform psychosocial intervention (e.g. cognitive behavioural therapy, psychoeducation, interpersonal and social rhythm therapy, etc.).

The BAS/BIS Questionnaire can also be used in the cases of criminal profiling. Previous research as reported by researchers MacAndrew and Steele in 1991 compared two groups on opposite spectrum levels of fear and the response of a variety of questions. The two groups in the study varied on levels of BIS, either high or low, and were selected by the researchers. One group was composed of women who had experienced anxiety attacks and together made up the high BIS group. The low BIS group was composed of convicted prostitutes who had been found to take part in illegal behaviour. Main findings showed that the responses to the questionnaires were distinctly different between the high BIS group and the low BIS group, with the convicted women scoring lower. Results from this study demonstrate that questionnaires can be used as a valid measurement to show differences in the behavioural inhibition systems of different types of people. Gray also introduced his SPSRQ questionnaire to measure sensitivity to reward (SR) and sensitivity to punishment (SP) in anxiety (2012). It is a specifically designed questionnaire linking to Gray’s theory referencing the SR to the BAS and the SP to the BIS.

Future Research or Implications

As mentioned previously, psychological disorders have been analysed in terms of the behavioural inhibition and activation systems. Understanding the differences between the systems may relate to an understanding of different types of disorders that involve anxiety and impulsivity. To date, there are many types of anxiety disorders that deal with avoidance theories and future research could show that the behavioural activation system plays a large role in such disorders and may have future implications for treatment of patients.

What is Behavioural Neuroscience?


Behavioural neuroscience, also known as biological psychology, biopsychology, or psychobiology, is the application of the principles of biology to the study of physiological, genetic, and developmental mechanisms of behaviour in humans and other animals.

Brief History

Behavioural neuroscience as a scientific discipline emerged from a variety of scientific and philosophical traditions in the 18th and 19th centuries. In philosophy, people like René Descartes proposed physical models to explain animal as well as human behaviour. Descartes suggested that the pineal gland, a midline unpaired structure in the brain of many organisms, was the point of contact between mind and body. Descartes also elaborated on a theory in which the pneumatics of bodily fluids could explain reflexes and other motor behaviour. This theory was inspired by moving statues in a garden in Paris. Electrical stimulation and lesions can also show the affect of motor behaviour of humans. They can record the electrical activity of actions, hormones, chemicals and effects drugs have in the body system all which affect ones daily behaviour.

Other philosophers also helped give birth to psychology. One of the earliest textbooks in the new field, The Principles of Psychology by William James, argues that the scientific study of psychology should be grounded in an understanding of biology.

The emergence of psychology and behavioural neuroscience as legitimate sciences can be traced from the emergence of physiology from anatomy, particularly neuroanatomy. Physiologists conducted experiments on living organisms, a practice that was distrusted by the dominant anatomists of the 18th and 19th centuries. The influential work of Claude Bernard, Charles Bell, and William Harvey helped to convince the scientific community that reliable data could be obtained from living subjects.

Even before the 18th and 19th century, behavioural neuroscience was beginning to take form as far back as 1700 B.C. The question that seems to continually arise is: what is the connection between the mind and body? The debate is formally referred to as the mind-body problem. There are two major schools of thought that attempt to resolve the mind–body problem; monism and dualism. Plato and Aristotle are two of several philosophers who participated in this debate. Plato believed that the brain was where all mental thought and processes happened. In contrast, Aristotle believed the brain served the purpose of cooling down the emotions derived from the heart. The mind-body problem was a stepping stone toward attempting to understand the connection between the mind and body.

Another debate arose about localisation of function or functional specialisation versus equipotentiality which played a significant role in the development in behavioural neuroscience. As a result of localisation of function research, many famous people found within psychology have come to various different conclusions. Wilder Penfield was able to develop a map of the cerebral cortex through studying epileptic patients along with Rassmussen. Research on localisation of function has led behavioural neuroscientists to a better understanding of which parts of the brain control behaviour. This is best exemplified through the case study of Phineas Gage.

The term “psychobiology” has been used in a variety of contexts, emphasizing the importance of biology, which is the discipline that studies organic, neural and cellular modifications in behaviour, plasticity in neuroscience, and biological diseases in all aspects, in addition, biology focuses and analyses behaviour and all the subjects it is concerned about, from a scientific point of view. In this context, psychology helps as a complementary, but important discipline in the neurobiological sciences. The role of psychology in this questions is that of a social tool that backs up the main or strongest biological science. The term “psychobiology” was first used in its modern sense by Knight Dunlap in his book An Outline of Psychobiology (1914). Dunlap also was the founder and editor-in-chief of the journal Psychobiology. In the announcement of that journal, Dunlap writes that the journal will publish research “…bearing on the interconnection of mental and physiological functions”, which describes the field of behavioural neuroscience even in its modern sense.

Relationship to Other Fields of Psychology and Biology

In many cases, humans may serve as experimental subjects in behavioural neuroscience experiments; however, a great deal of the experimental literature in behavioural neuroscience comes from the study of non-human species, most frequently rats, mice, and monkeys. As a result, a critical assumption in behavioural neuroscience is that organisms share biological and behavioural similarities, enough to permit extrapolations across species. This allies behavioural neuroscience closely with comparative psychology, evolutionary psychology, evolutionary biology, and neurobiology. Behavioural neuroscience also has paradigmatic and methodological similarities to neuropsychology, which relies heavily on the study of the behaviour of humans with nervous system dysfunction (i.e. a non-experimentally based biological manipulation).

Synonyms for behavioural neuroscience include biopsychology, biological psychology, and psychobiology. Physiological psychology is a subfield of behavioural neuroscience, with an appropriately narrower definition.

Research Methods

The distinguishing characteristic of a behavioural neuroscience experiment is that either the independent variable of the experiment is biological, or some dependent variable is biological. In other words, the nervous system of the organism under study is permanently or temporarily altered, or some aspect of the nervous system is measured (usually to be related to a behavioural variable).

Disabling or Decreasing Neural Function

  • Lesions: A classic method in which a brain-region of interest is naturally or intentionally destroyed to observe any resulting changes such as degraded or enhanced performance on some behavioural measure. Lesions can be placed with relatively high accuracy “Thanks to a variety of brain ‘atlases’ which provide a map of brain regions in 3-dimensional “stereotactic coordinates.
    • Surgical lesions: Neural tissue is destroyed by removing it surgically.
    • Electrolytic lesions: Neural tissue is destroyed through the application of electrical shock trauma.
    • Chemical lesions: Neural tissue is destroyed by the infusion of a neurotoxin.
    • Temporary lesions: Neural tissue is temporarily disabled by cooling or by the use of anaesthetics such as tetrodotoxin.
  • Transcranial magnetic stimulation: A new technique usually used with human subjects in which a magnetic coil applied to the scalp causes unsystematic electrical activity in nearby cortical neurons which can be experimentally analysed as a functional lesion.
  • Synthetic ligand injection: A receptor activated solely by a synthetic ligand (RASSL) or Designer Receptor Exclusively Activated by Designer Drugs (DREADD), permits spatial and temporal control of G protein signalling in vivo. These systems utilise G protein-coupled receptors (GPCR) engineered to respond exclusively to synthetic small molecules ligands, like clozapine N-oxide (CNO), and not to their natural ligand(s). RASSL’s represent a GPCR-based chemogenetic tool. These synthetic ligands upon activation can decrease neural function by G-protein activation. This can with Potassium attenuating neural activity.
  • Psychopharmacological manipulations: A chemical receptor antagonist induces neural activity by interfering with neurotransmission. Antagonists can be delivered systemically (such as by intravenous injection) or locally (intracerebrally) during a surgical procedure into the ventricles or into specific brain structures. For example, NMDA antagonist AP5 has been shown to inhibit the initiation of long term potentiation of excitatory synaptic transmission (in rodent fear conditioning) which is believed to be a vital mechanism in learning and memory.
  • Optogenetic inhibition: A light activated inhibitory protein is expressed in cells of interest. Powerful millisecond timescale neuronal inhibition is instigated upon stimulation by the appropriate frequency of light delivered via fibre optics or implanted LEDs in the case of vertebrates, or via external illumination for small, sufficiently translucent invertebrates. Bacterial Halorhodopsins or Proton pumps are the two classes of proteins used for inhibitory optogenetics, achieving inhibition by increasing cytoplasmic levels of halides (Cl) or decreasing the cytoplasmic concentration of protons, respectively.

Enhancing Neural Function

  • Electrical stimulation: A classic method in which neural activity is enhanced by application of a small electric current (too small to cause significant cell death).
  • Psychopharmacological manipulations: A chemical receptor agonist facilitates neural activity by enhancing or replacing endogenous neurotransmitters. Agonists can be delivered systemically (such as by intravenous injection) or locally (intracerebrally) during a surgical procedure.
  • Synthetic Ligand Injection: Likewise, Gq-DREADDs can be used to modulate cellular function by innervation of brain regions such as Hippocampus. This innervation results in the amplification of γ-rhythms, which increases motor activity.
  • Transcranial magnetic stimulation: In some cases (for example, studies of motor cortex), this technique can be analysed as having a stimulatory effect (rather than as a functional lesion).
  • Optogenetic excitation: A light activated excitatory protein is expressed in select cells. Channelrhodopsin-2 (ChR2), a light activated cation channel, was the first bacterial opsin shown to excite neurons in response to light, though a number of new excitatory optogenetic tools have now been generated by improving and imparting novel properties to ChR2

Measuring Neural Activity

  • Optical techniques: Optical methods for recording neuronal activity rely on methods that modify the optical properties of neurons in response to the cellular events associated with action potentials or neurotransmitter release.
    • Voltage sensitive dyes (VSDs) were among the earliest method for optically detecting neuronal activity. VSDs commonly changed their fluorescent properties in response to a voltage change across the neuron’s membrane, rendering membrane sub-threshold and supra-threshold (action potentials) electrical activity detectable. Genetically encoded voltage sensitive fluorescent proteins have also been developed.
    • Calcium imaging relies on dyes or genetically encoded proteins that fluoresce upon binding to the calcium that is transiently present during an action potential.
    • Synapto-pHluorin is a technique that relies on a fusion protein that combines a synaptic vesicle membrane protein and a pH sensitive fluorescent protein. Upon synaptic vesicle release, the chimeric protein is exposed to the higher pH of the synaptic cleft, causing a measurable change in fluorescence.
  • Single-unit recording: A method whereby an electrode is introduced into the brain of a living animal to detect electrical activity that is generated by the neurons adjacent to the electrode tip. Normally this is performed with sedated animals but sometimes it is performed on awake animals engaged in a behavioural event, such as a thirsty rat whisking a particular sandpaper grade previously paired with water in order to measure the corresponding patterns of neuronal firing at the decision point.
  • Multielectrode recording: The use of a bundle of fine electrodes to record the simultaneous activity of up to hundreds of neurons.
  • fMRI: Functional magnetic resonance imaging, a technique most frequently applied on human subjects, in which changes in cerebral blood flow can be detected in an MRI apparatus and are taken to indicate relative activity of larger scale brain regions (i.e., on the order of hundreds of thousands of neurons).
  • PET: Positron Emission Tomography detects particles called photons using a 3-D nuclear medicine examination. These particles are emitted by injections of radioisotopes such as fluorine. PET imaging reveal the pathological processes which predict anatomic changes making it important for detecting, diagnosing and characterising many pathologies.
  • Electroencephalography: Or EEG; and the derivative technique of event-related potentials, in which scalp electrodes monitor the average activity of neurons in the cortex (again, used most frequently with human subjects). This technique uses different types of electrodes for recording systems such as needle electrodes and saline-based electrodes. EEG allows for the investigation of mental disorders, sleep disorders and physiology. It can monitor brain development and cognitive engagement.
  • Functional neuroanatomy: A more complex counterpart of phrenology. The expression of some anatomical marker is taken to reflect neural activity. For example, the expression of immediate early genes is thought to be caused by vigorous neural activity. Likewise, the injection of 2-deoxyglucose prior to some behavioural task can be followed by anatomical localisation of that chemical; it is taken up by neurons that are electrically active.
  • MEG: Magnetoencephalography shows the functioning of the human brain through the measurement of electromagnetic activity. Measuring the magnetic fields created by the electric current flowing within the neurons identifies brain activity associated with various human functions in real time, with millimetre spatial accuracy. Clinicians can noninvasively obtain data to help them assess neurological disorders and plan surgical treatments.

Genetic Techniques

  • QTL mapping: The influence of a gene in some behaviour can be statistically inferred by studying inbred strains of some species, most commonly mice. The recent sequencing of the genome of many species, most notably mice, has facilitated this technique.
  • Selective breeding: Organisms, often mice, may be bred selectively among inbred strains to create a recombinant congenic strain. This might be done to isolate an experimentally interesting stretch of DNA derived from one strain on the background genome of another strain to allow stronger inferences about the role of that stretch of DNA.
  • Genetic engineering: The genome may also be experimentally-manipulated; for example, knockout mice can be engineered to lack a particular gene, or a gene may be expressed in a strain which does not normally do so (the ‘transgenic’). Advanced techniques may also permit the expression or suppression of a gene to occur by injection of some regulating chemical.

Other Research Methods

Computational models, i.e. using a computer to formulate real-world problems to develop solutions. Although this method is often focused in computer science, it has begun to move towards other areas of study. For example, psychology is one of these areas. Computational models allow researchers in psychology to enhance their understanding of the functions and developments in nervous systems. Examples of methods include the modelling of neurons, networks and brain systems and theoretical analysis. Computational methods have a wide variety of roles including clarifying experiments, hypothesis testing and generating new insights. These techniques play an increasing role in the advancement of biological psychology.

Limitations and Advantages

Different manipulations have advantages and limitations. Neural tissue destroyed as a primary consequence of a surgery, electric shock or neurotoxin can confound the results so that the physical trauma masks changes in the fundamental neurophysiological processes of interest. For example, when using an electrolytic probe to create a purposeful lesion in a distinct region of the rat brain, surrounding tissue can be affected: so, a change in behaviour exhibited by the experimental group post-surgery is to some degree a result of damage to surrounding neural tissue, rather than by a lesion of a distinct brain region. Most genetic manipulation techniques are also considered permanent. Temporary lesions can be achieved with advanced in genetic manipulations, for example, certain genes can now be switched on and off with diet. Pharmacological manipulations also allow blocking of certain neurotransmitters temporarily as the function returns to its previous state after the drug has been metabolised.

Topic Areas

In general, behavioural neuroscientists study similar themes and issues as academic psychologists, though limited by the need to use nonhuman animals. As a result, the bulk of literature in behavioural neuroscience deals with mental processes and behaviours that are shared across different animal models such as:

  • Sensation and perception.
  • Motivated behaviour (hunger, thirst, sex).
  • Control of movement.
  • Learning and memory.
  • Sleep and biological rhythms.
  • Emotion.

However, with increasing technical sophistication and with the development of more precise non-invasive methods that can be applied to human subjects, behavioural neuroscientists are beginning to contribute to other classical topic areas of psychology, philosophy, and linguistics, such as:

  • Language.
  • Reasoning and decision making.
  • Consciousness.

Behavioural neuroscience has also had a strong history of contributing to the understanding of medical disorders, including those that fall under the purview of clinical psychology and biological psychopathology (also known as abnormal psychology). Although animal models do not exist for all mental illnesses, the field has contributed important therapeutic data on a variety of conditions, including:

  • Parkinson’s disease, a degenerative disorder of the central nervous system that often impairs the sufferer’s motor skills and speech.
  • Huntington’s disease, a rare inherited neurological disorder whose most obvious symptoms are abnormal body movements and a lack of coordination. It also affects a number of mental abilities and some aspects of personality.
  • Alzheimer’s disease, a neurodegenerative disease that, in its most common form, is found in people over the age of 65 and is characterised by progressive cognitive deterioration, together with declining activities of daily living and by neuropsychiatric symptoms or behavioural changes.
  • Clinical depression, a common psychiatric disorder, characterised by a persistent lowering of mood, loss of interest in usual activities and diminished ability to experience pleasure.
  • Schizophrenia, a psychiatric diagnosis that describes a mental illness characterised by impairments in the perception or expression of reality, most commonly manifesting as auditory hallucinations, paranoid or bizarre delusions or disorganised speech and thinking in the context of significant social or occupational dysfunction.
  • Autism, a brain development disorder that impairs social interaction and communication, and causes restricted and repetitive behaviour, all starting before a child is three years old.
  • Anxiety, a physiological state characterised by cognitive, somatic, emotional, and behavioural components. These components combine to create the feelings that are typically recognised as fear, apprehension, or worry.
  • Drug abuse, including alcoholism.