A psychologist, H. J. Eysenck, and his colleagues at the University of London have spent years studying the differences between extraverts and introverts and have concluded that the primary distinction between the two is due to differences in arousability.
Eysenck notes that “extraverts may be characterized by low cortical arousal levels, introverts by high cortical arousal levels…these differences might be caused in turn by differential threshold levels in the reticular formation, whose main function is of course the control of arousal (and inhibition) levels in the cortex.”
What does this mean? The research shows that extroverted people have a low cortical arousal, so they are driven to seek stimulation that allows them to function normally. At the same time, introverted people possess such high cortical arousal levels that they seek to avoid stimulation so they can function normally. Extroverts are (outward-turning) stimulus seekers and introverts are (inward-turning) stimulus avoiders.
Apparently, there is “voluminous evidence” for Eysenck’s theory that helps us better understand these two personality types. Of course, neither of them are better than that other; they are each simply attempting to compensate (often unconsciously) for the natural levels of cortical levels that exist (or don’t exist) in their brain system.
Eysenck and his colleagues have also studied numerous factors relating to introversion and extroversion. The chart below displays discoveries made in one of those studies that relate to the four temperaments as they apply to factors of stability and instability in the studies of introversion and extroversion.
I thought you might find it interesting. Let me know in the comments where you land, or if you even find such charts compelling.
I find myself solidly on the Introverted side, and slightly leaning toward Unstable. (Should I be worried?)
The problem with descriptions like this and particularly with the images is that it inclines individuals to believe they fit in one quadrant or another. In reality we are looking at spectrums and the lines in the diagram should rightfully be removed.
I am on the introverted side; but how I respond at any given time depends entirely upon the situation. I tend to be most comfortable one-on-one and small groups. I have always held leadership positions, but prefer to work collegially and by consensus. I am talkative if it is an area of expertise or one I have interest in, otherwise I have no need to take up airtime. In short, though introverted, I can and have shown all the characteristics of an extrovert in particular situations. O much so that individuals who have seen me only or primarily in those situations are surprised that I am actually an introvert who very much enjoys quiet, peace, alone time, etc.