Child Temperament and the Brain

The last several decades have produced growing insights into the complex relationships between the brain and child temperament.

You may recall both the joy and apprehension of looking into the face of your newborn. While appreciating the beautiful hair, the soft skin, and the sweet breath, you may have also wondered how daring your daughter would be, or how shy your son might turn out. You were probably making predictions while your child was still in the womb. Would those third-trimester flutter kicks in your belly translate into a 6-year-old speedster racing across your recently vacuumed carpet with mud-stained shoes? What personality would your child have, and how would that temperament develop?

While there is still much to learn about temperament, here is a summary of the current state of brain science on child temperament. 

What is Temperament? 

Temperament refers to the differences between individuals apart from their genetics, learning, and environmental influences.

For those familiar with A.A. Milne’s Winnie-the-Pooh, you will find many of the classic temperaments embodied in those characters. No one can mistake the melancholic presentation of Eeyore, or Tigger’s boundless extraversion and novelty-seeking pattern of behavior. 

The word, temperament, comes from the Latin temperare meaning “to mix.” Early philosophers supposed that four internal fluids created our personalities: phlegm, blood, yellow bile, and black bile. The ratio of these fluids, they believed, could be seen in an individual’s personality. The idea may seem a bit silly, but you can see how these terms still exist in the words we sometimes use to describe personalities:

  • The phlegmatic personality is easygoing and relaxed.
  • The sanguine personality is social and pleasure-seeking.
  • The choleric personality is hot or “fiery.”
  • The melancholic personality is thoughtful, sad, and analytical.

Biological Basis of Temperament

Science continues to look for internal explanations for these expressions of personality. However, rather than relying on a fluid-based biology, our current focus is on neurotransmitters, such as serotonin, dopamine, norepinephrine, and GABA (gamma-aminobutyric acid).

Neurotransmitters function like batons in a race. Instead of passing a stick from one track star to another, the brain passes these chemicals from one neuron (brain cell) to another. These chemical messengers have different effects on the brain. While they influence the brain, therapy and medication can also affect them. (We’ll talk more about neurotransmitters later).

Nature vs. Nurture

Some take for granted that we are born with a particular personality and temperament. People have debated the topic of “nature vs. nurture” for a long time. Many people who didn’t hold the Christian faith have debated and investigated child temperament development and debated whether a child is more impacted by nature vs. nurture, and their work has often been revealing. As someone once noted, “All truth is God’s truth.”

Studies in Nature vs. Nurture

In his book The Four Temperaments of Children, written in the late 19th century, Bernhard Hellwig incorporated the four main temperament styles described above. He then attempted to apply his theory to the children he observed.

Hellwig found that many children did not easily fit into a particular category. He hypothesized that their environment may play a significant and influential role in a child’s temperament development. This is one version of the ongoing “nature vs. nurture” debate. Is a child’s temperament development a result of internal causes? Or does the outside world shape the inward disposition?

Put another way, are we like blank pages on which the environment (parents, siblings, early childhood experiences, etc.) write and shape us? Or are we born like seedlings, holding within us strong traits which blossom with time? 

Anna Freud, psychoanalyst and youngest daughter of Sigmund Freud, described her position on “nature vs. nurture” in her book Normality and Pathology in Childhood. She claimed that a child’s inner constitution has an influence on that child’s vulnerability to mental health struggles.

Carl Jung, a Swiss psychiatrist and psychoanalyst, offers a unique perspective on personality. He describes it as existing along three axes: intuition-sensation, thinking-feeling, and introversion-extraversion. These terms are popular in personality assessments and have become widely known. Some of these assessments are still in use today, including the Myers-Briggs Personality Inventory. 

In the battle of “nature vs. nurture,” Jung argued that nature, not nurture, had a stronger influence on temperament. He supported this idea by observing siblings within a family. He recognized how siblings had different personalities despite sharing the same environment.

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Big Five Model of Personality Traits

Researchers in the early 20th century began to use statistical techniques to design and analyze scientific studies. Their work led to identification of the “Big Five” model of personality traits. This model remains in use today. These five traits are openness, conscientiousness, extraversion, agreeableness, and neuroticism.

These five traits are more in keeping with the “nature” side of the nature vs. nurture debate. In the second part of the 20th century, several researchers began looking more at learning and experience (nurture) as the means to understanding temperament. Ivan Pavlov demonstrated learning through association; B.F. Skinner through punishment and reward. 

Stella Chess and Alexander Thomas, child psychiatrists and husband-and-wife research team, added observations and data. They suggested that innate temperamental styles are at play and may explain why loving parents may struggle with extreme behavior challenges from their child while some children raised in difficult conditions can seem more resilient.

In the last 40 years, there has been substantial research that recognizes the biological roots of personality. Despite this explosion of research, the media often views and presents temperament and psychiatric disorders as separate rather than related.

Today, the prevailing view in psychiatry is that children have an innate tendency toward personality traits that can be shaped, positively and negatively, by the environment. Nature and nurture stand together, like two pillars. 

Differences in Temperament Between the Sexes

While extraversion (outgoing, sociability) in kids has been found to be nearly equal among females and males, closer observation suggests there are differences between the sexes.

Young males in several studies demonstrated a higher degree of thrill and novelty-seeking behavior. Males, overall, were more active. Among females, negative emotions, sociability, affiliation (empathy), and self-regulating ability were greater. Put another way: One might expect stronger self-control, social adeptness, and emphasis on peer relationships among young girls than young boys.

Interestingly, the differences in these personality traits mirror and match the rates of certain psychiatric conditions. For instance, anxiety and depressive disorders (associated with personality traits of sociability and affiliation) are more prevalent in girls (particularly in adolescence). Autism and ADHD are more common in boys. Of course, this isn’t to say that girls can’t experience autism or boys won’t deal with anxiety disorders, but there is a strong association between sex and certain mental health conditions.

Brain Anatomy and Temperament

The brain is a complex organ with elegant structural design, much like a piano. Certain brain regions are like keys on the keyboard which can produce particular notes or functions. However, these regions are not just individually important. Instead, they often work in an orchestrated manner to perform complex tasks.

Currents of chemicals, such as hormones and neurotransmitters, also impact the brain. The brain can be seen as a circuit and measured by the amount of energy it produces (think of the electroencephalogram or EEG used in sleep, seizure, and other evaluations). The last several decades have produced growing insights into the complex relationships between these various ways of seeing the brain and child temperament development. 

Important Brain Structures

Several brain structures have received particular attention in current research. They include the nucleus accumbens (important in experiencing reward), hypothalamus (the link between our hormones and the nervous system), and the amygdala (responsible for processing emotions). Of these three structures, the amygdala deserves special notice as it influences many different parts of the brain.

The amygdala controls the “fight or flight response.” It also has influence over an important structure called the ventral prefrontal cortex (vPFC). The vPFC is important in helping us make big decisions in a crisis, assessing risk, and helping us to move into action. Think of the amygdala as the ignition switch of the car which turns on the engine (the vPFC).

In babies said to have colic (recall the similarity to choleric temperament discussed earlier), reports show the amygdala to be hyperactive. This hyperactivity leads to signs of agitation like flailing, kicking, and crying. However, as this child gets older, this hyperactive firing in the amygdala may produce shyness, which may sound counterintuitive. But when we look below the surface of behavioral inhibition (shyness) we might see accelerated heart rate, increased breathing rate, and pupil dilation – measurements we would have also detected in infancy if the child would have let us.

By contrast, studies have shown that a “daredevil” or adventure-seeking child (like the one you may have in your house) may actually have decreased firing of the amygdala. This can be evidenced by a low resting heart rate when engaged in “high stimulus” activity, like doing backflips off your couch.

Functional Connectivity

While brain research has focused on recognizing the important role of these discrete brain regions (amygdala, vPFC, and hypothalamus), recent research has also shed light on how interconnected the brain’s communication can be. This brain talk is referred to as “functional connectivity.”

For instance, the amygdala also talks to a region of the brain called the anterior cingulate cortex (ACC). The ACC is responsible for impulse control and decision making. In animal studies, the ACC appears to be part of the brain’s “cooling” system, which calms down the amygdala when it is fired up. One MRI study showed that anxious adults tended to have less connectivity between the ACC and the amygdala. This led researchers to conclude that if the ACC and amygdala are not linked well, the amygdala remains fired up when activated. It is then unable to cool down, making the anxiety stronger. Other studies suggest that the size of different brain regions are associated with child temperament development.  

Brain Chemistry

How do the neurotransmitters norepinephrine, dopamine, and serotonin connect to personality? Dopamine is important in motivation, reward, and attention. These traits are linked to extraversion and novelty-seeking (thrill-seeking behaviors). Activities that rapidly increase dopamine stimulate the nucleus accumbens (reward center) and can be highly reinforcing. This means that we like doing more of those things.

Serotonin and norepinephrine have long been identified as important influences on mood and anxiety. These chemicals are associated with shyness, negative emotion, and extraversion. 

Another potential influencer of personality traits is oxytocin. This hormone, known for its importance in lactation, is also related to parental bonding/attachment and social affiliation/belonging. This has caused researchers to speculate about whether oxytocin levels during pregnancy influence child development and whether oxytocin could be used therapeutically. 

The current research suggests that while genes may have some influence, it is much lower than one might expect. The influence of genetics appears to be more influential later in life. Consider puberty, where the genetic code for powerful anatomic changes does not activate until more than a decade into one’s life. Likewise, a person might be genetically predisposed to Alzheimer’s disease, but that does not manifest until late in a person’s life.

Between Personality and Pathology 

Psychiatry has begun to recognize that many mental health disorders occur on a continuum. Rather than saying a disorder suddenly appears from nowhere, or that for various conditions “you either have it or you don’t,” the field has begun recognizing a spectrum in which the disorder may range from slightly impairing to profound. The previous version of the psychiatric diagnostic manual made a significant distinction between general disorders and personality disorders. The newest edition of the manual has discontinued this categorization. 

Is there a clear line that separates personality traits from a diagnosable mental health disorder? Several factors determine the “line.” These factors include age and level of development. (There are many reasons, including genetic conditions, that a child’s developmental level might not align with his or her age). For instance, the level of inattentiveness and novelty-seeking seen in a preschool-aged child would be cause for concern in a 17-year-old. A psychiatric evaluation involves understanding a typical range of personality and developmental features.

Here’s a way to conceptualize where the “line” lies. We each have varying degrees of certain temperament traits. These include negative affect (negative emotion that influences behavior), extraversion, sociability, and the ability to regulate one’s behavior. The intensity of these traits can lead to behaviors and moods that can result in either strengths or barriers. Consider, for example, a child with autism spectrum disorder. Difficulties in back-and-forth conversation and connection characterize ASD. This corresponds with the temperament trait of low sociability. 


Neurotransmitters can be involved in both child temperament development and mental health disorders. When a child is having psychological or emotional difficulties, a mental health professional must determine how much of the situation is personality and how much is pathology. 

If medication for a particular issue is called for, parents will often ask for something that will help their child “without changing them.” As a physician and a father, I completely understand it.

Unfortunately, there are books and movies that make it seem as if child psychiatrists are eager to turn children into “zombies” or strip away their feelings. This, of course, is unacceptable, and I often reassure parents that this is not the goal of treatment. In fact, I tell parents that if their child’s treatment makes them sedate or less “themselves,” we should change course. This is an unacceptable side effect of medication.

And it should go without saying: Medication should never be used to “treat” a child’s personality.

A Delicate Balance

Still, it’s important to recognize that if personality traits occur on a spectrum between normal to pathological, treatment – with or without medication – runs the risk of altering elements of personality. Putting it another way, turning off all symptoms while leaving someone’s personality completely unchanged requires a delicate balance. We see this in other areas of medicine. For example, eradicating cancer with medication involves, at least temporarily, losing healthy cells while primarily targeting malignant ones. The aim is to take care of the problem in a way that avoids negative side effects.

It is important to recognize that, especially in the lives of children, young brains are continuously developing. Because of this, the need for interventions should regularly be revisited.

Also, there is no blanket answer regarding whether to treat with medication or not. Ultimately, the decision should be arrived at prayerfully and with honest and thoughtful discussion with all parties involved.

Final Thoughts

While there is still much to learn about child temperament development, we are constantly discovering links between how the brain’s chemistry and anatomy has an impact on child temperament. The structure and behavior of the brain have a significant impact on child temperament, as well as, the nurturing of their environment. The nature vs. nurture debate has shown that both sides are equally as important to child temperament development and behavior.

© 2020 by Dr. Larry Mitnaul. All rights reserved. 

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