Neurodiversity Part 6:
Research on Behavioral Systems

As mentioned in Part 2, human behavior research into introversion and extroversion does not align with the public view of these terms. It isn't culled down to how shy or outgoing a person is. And the research dating back to brain scans in the 1960's and 70's shows similarities to the public definition of neurodiversity (coined in the 1990's by Judy Singer.)

Part 3 looked at blood flow in the brain.
Part 4 went over cortical arousal.
Part 5 discussed anticipatory reactions.

And now we're taking a look at behavioral systems. After this, we'll have two more parts on a baseline model for neurodivergence, and how it relates to diagnoses like ASD and ADHD.

Also, here is a link to the seven executive functions listed in a Psychology Today article for reference.

Behavioral Inhibition & Activation Systems (BIS, BAS)
As a follow up to Eysneck’s work, JA Gray outlined the biopsychological theory of personality which included the behavioral inhibition and activation systems. (Source) It’s believed that an individual has access to both appetitive and aversion motivation as needed. However, Gray discussed how introverts were more sensitive to the inhibition system while extroverts were more sensitive to the activation one.

Here’s a high-level break down of the two systems.

Behavioral Inhibition System (BIS):

  • "Aversive motivational system" (Source)
  • "Inhibits behavior in response to signals of punishment, non-reward, and novelty." (Source)
  • "Associated with feelings of anxiety and avoidance behaviors." (Source)
  • "Higher BIS scores showed greater relative right prefrontal activation." (Source)
  • "People with high BIS sensitivity may not experience much anxiety and other negative effects if their environments (by chance or by design) do not present significant BIS-activating events." (Source)
  • "People with greater BIS sensitivity may recognize the potential for negative events more readily and may actively avoid such situations." (Source)

Behavioral Activation System (BAS):

  • "Appetitive motivational system" (Source)
  • "Activates behavior in response to signals of reward and nonpunishment." (Source)
  • "Associated with feelings of hope and approach behaviors." (Source)
  • "Higher BAS showed more relative left prefrontal activation." (Source)
  • "People with high BAS sensitivity may not experience substantial positive affect if their environments do not provide reward-eliciting events to activate the BAS." (Source)
  • "People with greater BAS sensitivity may seek out situations in which positive events are more likely to occur." (Source)

Again, this doesn't mean that introverts solely utilize the Behavioral Inhibition System or that extroverts rely only on the Behavioral Activation System. But it can help us understand why introverts may not be as likely to take risks as others, why they can be more sensitive to rejection, and even why they may anticipate negative outcomes in if they've had bad experiences before.

Ultimately, BIS and BAS reliance may affect the following executive functions: self-awareness, inhibition, nonverbal working memory, emotional regulation, motivational regulation, and planning and problem-solving.

Struggling with either aversive or appetitive motivation is something therapists can help with. (Feeling burned out or dealing with addiction are a few examples.) But it's also why it's important to understand how to structure rewards and consequences when trying to motivate yourself. If you are burned out, finding milestone rewards in the short-term (while making a long-term plan) can keep you from falling behind or self-sabotaging. Also knowing the types of things that can lead to addiction for you can help you find other alternatives. I'll cover that more in the serotonin- and dopamine-based rewards series.

Onto Part 7 >

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