©Arlene R. Taylor PhD
PET scan studies by Dr. Debra Johnson have shown that brain blood-flow rates differ in extroverts versus introverts. Some of the behavioral differences between extreme extroverts and extreme introverts may result from using different brain pathways that influence where the individual directs his/her focus—internally or externally.
Extraverts 16% *
*Eysenck Personality Questionnaire. Extraverts/extroverts, according to Eysenck's theory, are chronically under-aroused and bored and are therefore in need of external stimulation to bring them up to an optimal level of performance. About 16 percent of the population tend to fall in this range. Introverts, on the other hand, (also about 16 percent of the population) are chronically over-aroused and jittery and are therefore in need of peace and quiet to bring them up to an optimal level of performance. Most people (about 68 percent of the population) fall in the midrange of the continuum, an area referred to as ambiversion.
(http://en.wikipedia.org/wiki/Eysenck_Personality_Questionnaire) Accessed 12/13.