The BIS/BAS/Fight Flight Freeze system

Author: Ulrich Brennecke
Review: Dipl.-Psych. Waldemar Zdero

Mammals react differently to stress. Some react more with attack and fight, others with flight or playing dead.
These differences in stress reactions are not very hereditary, but rather randomly distributed personality patterns. They were developed in the course of evolution to increase the probability of survival of groups. Heterogeneous groups have a higher chance of survival than homogeneous groups. This principle can be found today in industrial psychology. Groups with different personality types are more productive in the long term, especially if they can understand and recognize the different characteristics.

Gray’s fight/flight stress model distinguishes between 3 functional stress response systems.

• the BAS system controls the attack
• the FFFS type controls escape and playing dead
• the BIS system is responsible for balancing BAS and FFFS.
  High activation of BIS is associated with anxiety and introversion, while high activation of BAS causes impulsivity and extraversion.
  The BAS is controlled by the dopaminergic system, while the BIS is controlled by the noradrenergic-cholinergic-serotonergic neurotransmitters. The FFFS, which triggers flight, fight or flight to death, is controlled in the periaqueductal gray area of the brain.

• 1. The BIS/BAS/FFS system according to Gray
  • 1.1. Reinforcement Sensitivity Theory (RST)
    • 1.1.1. The modified RST (Gray, 2000)
    • 1.1.2. The original RST (Gray, 1990)
• 2. Behavioral Inhibition System (BIS)
  • 2.1. BIS according to the old RST
    • 2.1.1. Activation of the BIS
    • 2.1.2. Effects of the BIS
  • 2.2. The BIS according to the new RST
  • 2.3. BIS and neurophysiological correlates
• 3. Behavioral Activation System (BAS)
  • 3.1. BAS according to old and new RST
  • 3.2. Effects of the BAS
  • 3.3. Neurophysiological correlates of the BAS system
• 4. Fight-Flight-Freeze-System (FFFS) according to new RST

1. The BIS/BAS/FFS system according to Gray¶

Mammals do not react uniformly to stress.
According to the fight/flight stress model (by Connor (1932) and later Gray, who combined it with the BIS/BAS model, → RST from 1990, revised 2000), there are 2 to 3 main groups of stress reactions:

The BAS type reacts to stress by attacking.
The FFFS type reacts to stress by fleeing or playing dead.
According to the revised Reinforcement Sensitivity Theory (RST) by Gray (2000), the BIS system no longer reacts to external stimuli, but only becomes active when the BIS and the FFFS system have both been activated. The BIS system is responsible for balancing BAS and FFFS.

The original Fight/Flight system has been expanded to include the Freeze component to create the FFFS.

1.1. Reinforcement Sensitivity Theory (RST)¶

Whether BIS and BAS are independent of each other, i.e. BIS and BAS can both be low or at different levels (according to Gray), or whether BIS and BAS are the poles of a uniform unit within which they correlate with each other depending on the state (Corr), i.e. are rigidly connected to each other rather like a playground seesaw, was disputed. However, the question should be obsolete with the newer RST, because with this BIS and FFFS must necessarily be active at the same time in order to be able to offer the BIS alternative courses of action. More recent voices consistently consider the systems to be independent of each other.⁵⁶

1.1.1. The modified RST (Gray, 2000)¶

In 2000, Gray modified the reinforcement sensitivity theory (RST) he postulated, particularly with regard to the task of the BIS.

According to the modified RST, the BAS and FFFS are activated simultaneously and independently of each other by new stimuli. The BAS reacts to reward stimuli, the FFFS to all Forms of punishment stimuli. The BIS, on the other hand, is no longer activated by stimuli themselves, but only by simultaneous activation of the BAS and FFFS. The BIS is then activated by conflicts between BAS and FFFS and serves to weigh up which system should be given preference for action. At the same time, the BIS activates attention to the environment in order to obtain cues for decision-making.⁷⁸

Impulsivity can then be described as high extraversion with high emotional instability (neuroticism), which leads to a high sensitivity to reward (highly reactive BAS).

1.1.2. The original RST (Gray, 1990)¶

The “old” RST, according to which the BAS system should react to reward stimuli, the BIS to punishment stimuli and non-reward, and the FFS to existentially threatening stimuli, with these three systems acting independently of each other, could not conclusively explain a number of reactions.

2. Behavioral Inhibition System (BIS)¶

2.1. BIS according to the old RST¶

The Behavioral Inhibition System correlates with personality traits⁹

• Anxiety
  • As a weakened form of neuroticism
  • Marker for the sensitivity to punishment (Trait Sensitivity of Punishment, SP)
• Introversion (as the antithesis of BAS extraversion)
• Fear

The BIS reflects susceptibility to punishment, non-reward and unknown stimuli (conditioned aversive stimuli).

2.1.1. Activation of the BIS¶

The BIS is activated by

• Conditioned stimuli for
  • Punishment
  • Frustrating non-reward
  • New, unexpected stimuli

These trigger a behavioral inhibition via the BIS.

The BIS is noradrenergic-cholinergic-serotonergic controlled¹⁰ and can be impaired by anxiolytics.¹¹

2.1.2. Effects of the BIS¶

In a diary study, people with high BIS reported more negative experiences and experienced them more negatively than comparison groups.¹²
People with high BIS evaluate negative social experiences more negatively. They invest more to avoid them and experience negative experiences more intensely.¹³, page 227, with further evidence))

People with high BIS are more likely to set negative goals. Example in the social domain: “I don’t want to be alone” instead of “I want to have a partner”.¹³, page 227, with further evidence))

Nevertheless, the choice of (here: social) goals is a better predictor of (here: social) success than the degree of sensitivity to punishment or reward (BIS and BAS).¹³, page 227, with further evidence))

2.2. The BIS according to the new RST¶

See above under 1.1.1.

2.3. BIS and neurophysiological correlates¶

A higher BIS correlates with greater right prefrontal activation, shows lower NK activity (NK = natural killer cells) and reacts more strongly to negative emotional stimuli.¹⁴

Neurologically, Gray locates the BIS in the septo-hippocampal system (SHS),¹⁵ consisting of

• Hippocampus (limbic system)¹⁵
• Septal cores¹⁵
• Connections to the cingulate cortex, part of the frontomedial PFC¹⁵
• Connections to the PFC¹⁵
• Amygdala¹⁶

An activated BIS increases non-specific arousal, which leads to a focus of attention on currently relevant events.¹⁷
High anxiety and increased sensitivity to punishment are characterized in particular by a high synchronization of the hippocampus and amygdala in the theta EEG frequency band.¹⁸ With a reduction in anxiety through new conditioning, the synchronization of hippocampus and amygdala decreases at the same time.¹⁹²⁰

Depression and anxiety disorders are associated with a sensitized BIS.²¹ A sensitized BIS is associated with increased sensitivity to punishment and an enlarged hippocampus and amygdala.²²¹⁸

Anxiolytics (anxiety-reducing drugs) reduce the excitability of the amygdala.²³

However, the BIS system can also be impaired by anxiolytics.²⁴

The BIS is regulated by the neurotransmitters

• Noradrenaline¹⁵²⁵¹⁷
• Serotonin¹⁵²⁵¹⁷
• Acetylcholine²⁵

where noradrenaline and serotonin are linked to the activity of the hypothalamic-pituitary-adrenal axis (HPA axis) and lead to the release of cortisol from the adrenal gland.²⁶ In healthy children, activation of the BIS in response to punishment is associated with increased cortisol levels following difficult situations.²⁷

Chiossi summarizes the neurological correlates of BIS.²⁸

3. Behavioral Activation System (BAS)¶

3.1. BAS according to old and new RST¶

According to Gray’s Reinforcement Sensitivity Theory (RST), Drive, Reward Responsiveness, Fun Seeking²⁹ correlate with the degree of activation of the BAS to a particular stimulus.
The BAS reacts to conditioned stimuli for reward and non-punishment, which leads to approach behavior and generally to behavioral activation.³⁰³¹

The Behavioral Activation System correlates with the personality trait impulsivity as a weakened form of extraversion and reflects sensitivity to reward incentives.³²³³

When the BAS is activated, this leads to a feeling of reward similar to that experienced after the consumption of cocaine, amphetamines, heroin or alcohol.³⁴ These rewards are all linked to the dopaminergic system.

3.2. Effects of the BAS¶

In a diary study, people with a high BAS reported more positive experiences than a comparison group.¹²
People with a high BAS are more likely to set positive goals. Example in the social domain: “I want to meet new people” instead of “I don’t want to be alone”.¹³, page 227, with further evidence))
Nevertheless, as already written, the choice of (here: social) goals is a better predictor of (here: social) success than the degree of sensitivity to punishment or reward (BIS and BAS).¹³, page 227, with further evidence))

3.3. Neurophysiological correlates of the BAS system¶

The BAS is primarily dopaminergically controlled by the mesocortical pathway.²⁵

The BAS is controlled neurologically by processes that take place in the brain areas

• Basal ganglia
  • Pallidum
    • Dorsal
    • Ventral
  • Striatum
    • Dorsal
    • Ventral
• Dopaminergic nerve pathways

lie.³⁵

The fact that the BAS is primarily dopaminergically controlled by the mesocortical pathway²⁵ explains the vulnerability of the reward system in ADHD due to the dopaminergic dysfunctions known to occur in ADHD.

A start of the BAS is reflected in an increase in the heart rate³⁶³⁷ and an increase in skin conductance as well as changes in the startle reflex.³⁸

Children with the ADHD-HI subtype and with social disorders were found to have reduced activity of the BIS and increased activity of the BAS.³⁹²⁶ Under the new RST, not the BIS but the FFFS is likely to be reduced.
The response to recurring reward stimuli was reinforced, even if these had been replaced by aversive stimuli in the meantime. ⁴⁰

4. Fight-Flight-Freeze-System (FFFS) according to new RST¶

The FFFS correlates with panic and fear (threat), i.e. unconditioned aversive stimuli. Primary negative reinforcers are supported by negative emotions such as horror, panic and anger and trigger flight, freeze or fight.⁴¹
The FFFS is anchored in the vegetative nervous system.

The recognized therapy method of mindfulness-based stress reduction (MBSR) for ADHD has a vegetative effect.

The fight-flight-freeze mechanism (first described by Gray) is controlled in the periaqueductal gray of the brain (central cave gray). The control mechanism is still unknown.⁴²