HOW DOES THE BRAIN MAP AND FUNCTION OF AN INTROVERT DIFFER TO THAT OF AN EXTROVERT?

Shreya Verma (OHS)

The brain of an elephant is three times larger than a human brain, yet humans are so much more advanced than elephants. Intrigued by this, scientist embarked on their journey of human brain mapping. Mapping the very object that controls every single person on Earth to discover exactly which parts of the brain correspond to their specific functions. What part makes us analytical? What part makes us emotional? What makes some quieter than others? The idea of brain mapping was initially considered in the 1880s when Angelo Mosso invented the ‘human circulation balance’ which was the first neuroimaging machine. It non-invasively measured the distribution of blood in the brain when performing emotionally or intellectually stimulating tasks. This was the basis for more advanced and safer neuroimaging techniques that are present now, such as magnetic resonance imaging (MRI) and positron emission tomography (PET) scans, which are able to monitor the brain whilst performing different activities, and therefore observe how different people’s brains react to the same events. The terms ‘extrovert’ and ‘introvert’ were derived by Carl Jung, a Swiss psychologist, who explained ‘extroverts’ to be those who gain energy from social interaction and ‘introverts’ to be those who find social events draining. Although these terms are fairly subjective and definitely not as black and white as they are defined; there must be some variance in brain function to depict such different personality traits in terms of extroversion and introversion. This, therefore, shows the complexity of the human brain, as, unlike an organ such as the liver, it is able to change and cater its functions, in terms of personality and emotions, depending on the person and of course the person’s genes. Thus, this allows scientists and psychologists to link the variety of personality differences, such as those in extroverts and introverts, to brain function. Research has shown that the brain of an extrovert requires more dopamine than an introverts’ in order to feel the same amount of happiness, which explains why extroverts are typically looking for more social interaction and additional conversation to release dopamine. Alternatively, introverts’ brains are a lot more sensitive to dopamine, and so feel over stimulated when they get too much of it. Instead, PET scans have shown an increased blood flow through the acetylcholine pathway in introverts, which is a chemical released when performing a stimulating activity such as reading a book. Although both acetylcholine and dopamine are typically ‘happy hormones’; dopamine is responsible for the more urgent jolts of happiness that we get when taking risks, whilst acetylcholine allows us to feel content and relaxed. Importantly, the dopamine pathway is shorter than the acetylcholine pathway which tells us that extroverts are likely to gain happiness from events quicker than introverts are. These differences in pathways monitored by brain imaging and mapping also play a part in proving the typical stereotype that introverts are prone to over thinking. As mentioned, the greater blood flow through the dopamine pathway in extroverts means that outside information, such as a voice, travels quickly through areas in the brain that control sight, sound, taste and touch. For introverts, however, information travels along the acetylcholine pathway, which, as it’s longer, allows the external material to pass through multiple areas of the brain. These include the right front insular which regulates empathy; the Broca’s area which controls speech; the right and left frontal lobes which allow judgement and impulsiveness and the hippocampus which controls memory. Hence, as information is assessed by multiple stations in the brain of an introvert, a significant amount of thinking occurs. This perhaps suggests why introverts become overstimulated quickly too. Furthermore, due to the fact that the majority of introverts are over thinkers, a growing population of researchers suggest that they are therefore more prone to mental health disorders, such as depression. The fact that introverts are likely to isolate themselves from others also contributes to this. However, there are arguments likewise implying that extroverts are more likely to experience depression, as they are essentially searching for more dopamine from external sources, which is unlikely to be present at all times. Thus, this shows that the link between personality traits and mental health problems are key in not only development of research around the topic, but also in helping those who are struggling with their mental health. Additionally, research has shown that extroverts lack grey matter in their prefrontal cortex, whilst it appears significantly thicker and larger in introverts. Grey matter is supposedly the most interesting part of the brain, as this is where the information from sensory neurones is processed, and so the area that is associated with decision making. The fact that introverts have more of this confirms their ability to sit quietly and think over situations well, whilst extroverts much rather jump into risks without assessing them. All of these factors contribute to what makes extroverts extroverted and introverts introverted. The fact that their brains and biological pathways differ tells us that a person is born with the innate ability to be

extroverted or introverted. However, often we meet people who resemble themselves as both an extrovert and an introvert, or an ambivert. Studies have shown that typically younger people on the whole are more extroverted, and become progressively introverted as they age. From evolution’s point of view, it’s favourable for one to be more extroverted when they’re young as it makes it easier to find someone and mate. Thus, this helps to explain those ambivert personalities as even introverts can express extrovert qualities in their youth. Although, nevertheless, introversion and extroversion and definitely not two mutually exclusive categories and it is easy for a person to possess characteristics of both. The fact that people in general become more introverted with age, however, sparks the question of why and what changes occur in the brain for this to happen…

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