Biological Determinants and Animal Behavior Applications

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Biological Determinants and Animal Behavior Applications

Psychology of Personality · Chapter 6: Biological and Evolutionary FoundationsSection 6.3 · lesson 37 of 8310 min · free with a free account

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In this lesson

Systems that shape behaviour, and are remodelled by it.

  • Name the biological systems linked to personality traits
  • Summarise Eysenck's arousal account of extraversion
  • Explain what behavioural syndromes in animals show
  • State why causal direction is hard to establish here

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Everything said in the video, section by section (1,249 words). Read along, or search it.

Biological and Evolutionary Foundations

Biological Determinants

Suppose you find that people high in a trait also differ in some brain system. The obvious reading is that the biology is causing the trait. But experience remodels those same systems, continuously. So the arrow could point either way, and often points both ways at once. That problem sits underneath everything in this section. We will name the biological systems linked to personality traits. Summarize Eysenck's arousal-based account of extraversion. Look at what stable temperament in other species actually shows. And be clear about why causal direction is so hard to establish here.

Get Concrete

Beyond Genes in the Abstract

The previous section dealt in heritability estimates, which are abstract by design. This one deals in machinery. Personality is shaped by concrete biological systems. Brain structures. Neurotransmitters. Hormones. The proposal is that differences in the sensitivity of these systems matter. And that they help explain why people vary in extraversion, impulsivity, and emotional stability. Take one example. Individual differences in reward-related brain circuits. These are associated with how strongly a person seeks novelty and social stimulation. Note the word associated. It will keep appearing, and it is not a synonym for causes.

The Systems

Several Inputs, One Temperament

It is worth holding the main systems in view together. Dopamine, associated with reward and approach behaviour. Serotonin, associated with mood regulation and impulse control. Cortisol, a stress hormone tied to the stress response. Testosterone, associated with dominance. And the amygdala, involved in fear processing. All of them feed into what we observe as temperament. But notice the shape of that. Several inputs, converging. Which is why no one of them can be read off from a person's behaviour.

The Links

What Each System Is Associated With

Take the links one at a time, as the source states them. Dopamine is linked to reward sensitivity and approach behaviour. In trait terms, to novelty seeking and extraversion. Serotonin is linked to mood regulation and impulse control. In trait terms, to emotional stability. Stress hormones such as cortisol are associated with reactivity under threat, and with anxiety. Hormones like testosterone have been associated with dominance and competitiveness. And the amygdala, through fear processing, is linked to behavioural inhibition. Now the warning that belongs with all of this. These systems do not act in isolation. Personality emerges from their balance and interaction. Not from any single chemical. Which is why the popular version, where one chemical explains one trait, is always too simple.

Both Ways

The Inputs Are Not Fixed Inputs

Here is the complication that reorganizes everything else in the section. These biological systems are themselves shaped by experience. Repeated stress can recalibrate cortisol responses. Rewarding or depriving environments can alter dopamine signalling over time. So the biological determinants of personality are not fixed inputs. They are living systems. They influence behaviour, and they are remodeled by it. That is why the causal question here is genuinely hard. If you find a difference in someone's stress response, you have not learned where it came from. It could be a starting condition. It could be a record of what they have lived through. Any claim that biology causes a trait has to survive that ambiguity first.

Eysenck

The Introvert Is Already Stimulated Enough

Several influential trait theories are grounded directly in biology. The best known is Eysenck's account of extraversion. He proposed that extraversion reflects differences in cortical arousal. That is, differences in baseline brain activation. Introverts, on this account, are more easily over-stimulated. And so are inclined to avoid intense input. Extraverts seek out stimulation, in order to reach a comfortable level. The elegant part is what the two groups have in common. Both are regulating toward a comfortable level of arousal. They differ in where that level starts. Not in what they are trying to achieve.

Two Systems

Sensitive to Reward, Sensitive to Punishment

Other models work from two systems rather than one dimension. A behavioural approach system, sensitive to reward and incentive. And a behavioural inhibition system, sensitive to punishment and threat. These are linked to traits such as impulsivity and anxiety. The useful feature is that the two systems are treated as independent. Which means a person can be strongly drawn toward rewards. And strongly alarmed by threats. At the same time, without contradiction. Underneath both Eysenck and these models sits one general principle. Stable traits often correspond to stable differences in how nervous systems respond. To reward, to threat, and to stimulation.

Why It Helps

Testable Predictions, Imperfect Maps

So what are these biologically anchored theories actually good for? Their real value is that they generate testable predictions. Predictions connecting brain function to behaviour. Which means predictions that can come back wrong, and sometimes do. That is worth more than explanatory reach. But state the limit alongside the strength. No theory maps a trait perfectly onto a single brain system. What the evidence supports is a broad correspondence. Not a one-to-one translation between a trait and a piece of biology. Keep the two claims attached to each other. A broad correspondence is a genuine finding. It is also a much weaker claim than the popular retelling makes it sound.

Not Only Us

Animals Have Stable Individual Differences Too

Personality-like consistency turns out not to be unique to humans. Researchers have documented stable individual differences in other species. These are often called animal temperament, or behavioural syndromes. And they have been found in species ranging from insects to primates. Animals reliably differ in boldness, aggression, sociability, and exploration. Now the property that makes this interesting. These differences predict behaviour across situations. Much as human traits do. That cross-situational consistency is exactly what makes something trait-like. Rather than just a reaction to whatever is happening at the time.

What It Buys

Experiments You Cannot Run on People

Comparative study is valuable for two quite different reasons. The first is methodological. It allows controlled breeding and experimentation that is impossible in humans. Which helps isolate genetic and neural contributions. The second is theoretical. It reveals evolutionary continuity. Suggesting the biological machinery underlying temperament is ancient, and widely shared. You can see the everyday version of this without a laboratory. Dog breeders and trainers routinely observe stable temperament differences. Some dogs are consistently bold and exploratory. Others are cautious and reserved, across many situations. And the traffic runs both ways. Animal findings inform theories of human personality, and are informed by them.

The Ledger

Strengths and the Limits That Come With Them

Set the strengths and the limits side by side, because they belong together. The approach grounds personality in measurable physiological systems. It connects psychology to neuroscience and genetics. It produces falsifiable hypotheses. And animal and twin research add converging evidence. Now the limits, which must be respected rather than mentioned in passing. Correlations between biology and behaviour are often modest. The direction of causation can be unclear, since experience itself shapes the brain. And reducing personality entirely to biology risks neglecting culture, learning, and meaning. So the most defensible position is a layered one. Treat biological systems as one essential layer of a larger, interactive account. Essential, and one layer. Not the whole account.

Consolidate

Tendencies, Not Destinies

Recognizing the biological substrate does explain real things. Why some traits emerge early, and remain stable. Why certain dispositions run in families. And why temperament can be observed before culture and learning have had much chance to operate. It also clarifies why purely environmental accounts of personality are incomplete on their own. But the same evidence cautions against fatalism, and this is the part to carry away. Because the systems involved are responsive to experience. Biological predisposition sets tendencies rather than destinies. So when a trait is tied to a brain or hormone system, remember two qualifiers. The link is usually probabilistic. And it is bidirectional. Biology shapes behaviour, and experience reshapes biology. Neuroscience and genetics describe the starting conditions, and the ongoing constraints. Within which experience, choice and culture continue to shape the person.

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FAQ

Questions students ask us

About Biological Determinants and Animal Behavior Applications

Which brain chemicals and hormones are linked to personality?
Dopamine is linked to reward sensitivity, novelty seeking, and extraversion; serotonin to mood regulation, impulse control, and emotional stability; cortisol to stress reactivity and anxiety; and testosterone to dominance and competitiveness. The amygdala, through fear processing, is tied to behavioral inhibition. These are associations, not single causes: traits emerge from many interacting systems, and experience such as chronic stress can reshape them.
What is Eysenck's arousal theory of extraversion?
Hans Eysenck proposed that extraversion reflects differences in cortical arousal, or baseline brain activation. Introverts are more easily over-stimulated, so they tend to avoid intense input, while extraverts seek stimulation to reach a comfortable level. Both groups are regulating toward a comfortable level of arousal; they differ in where their baseline starts. The theory matters because it makes testable predictions linking brain function to behavior.
What are the behavioral approach system and behavioral inhibition system?
These are two biological systems, associated with Jeffrey Gray's reinforcement sensitivity theory. The behavioral approach system responds to reward and incentive and is linked to impulsivity, while the behavioral inhibition system responds to punishment and threat and is linked to anxiety. Because the systems are treated as independent, a person can be strongly drawn to rewards and strongly alarmed by threats at the same time.
Do animals have personalities?
Many animals show stable individual differences, often called animal temperament or behavioral syndromes, in species ranging from insects to primates. Individuals differ reliably in boldness, aggression, sociability, and exploration, and these differences predict behavior across situations, as human traits do. Dog breeders, for example, see consistently bold or cautious dogs. Animal research allows controlled breeding and suggests the biology of temperament is ancient and widely shared.

About the Psychology of Personality course

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Psychology of Personality (Psychology 300) carries a NCCRS credit recommendation for 3 semester credits. ACE and NCCRS have over 2,100 cooperating colleges that will consider accepting credits; the final decision is with the universities.
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