©Arlene R. Taylor PhD

The terms Extroversion, Ambiversion, and Introversion refer to the brain’s innate set-point of alertness and indicate the amount of stimulation in the environment that is optimum for a given brain. Think of your set-point as the typical, innate, stable level at which your brain and body function most energy-efficiently. Located in the first brain layer, Reticular Activating System (RAS) is believed to create this set-point, referred to by some as a person’s arousal or alertness level.

Some believe that a person’s position on the Extroversion-Ambiversion-Introversion (EAI) Continuum is more primary than even brain bent.

Hans Eysenck’s research led him to believe that the brains of human beings can be distributed along a metaphorical EAI Continuum based on their innate set-point:

• 15% to 16% are estimated to be very alert when fully awake (Introverts). These individuals tend to seek lower than average levels of stimulation in order to avoid being overwhelmed.

• 15% to 16% are estimated to be much less alert when fully awake (Extroverts). These individuals tend to seek higher than average levels of stimulation in order to feel alive and alert.

• 68% to 70% are estimated to fall in the middle of the continuum and are moderately alert when fully awake (Ambiverts). These individuals tend to function best with moderate or average levels of stimulation.

Some newer dictionaries list two spellings: Extroversion and Extraversion. Both terms refer to the same concept. Extroversion is the more common spelling and is the spelling used on this website.

My goal is to stimulate your thinking and observation, trigger increased awareness at an individual level, jumpstart your application of the information to everyday living, and provide options for behaviors that are more likely to result in positive outcomes. Although I have relied heavily on brain function research, a plethora of studies, and discussions with brain researchers and other experts, the summaries represent my own brain’s observations and opinions.

Typically, conclusions from research projects and studies are presented in the form of generalizations. They apply to about two-thirds of the population (e.g., the red portions on the drawing of the Bell Curve of distribution that represent the first standard deviation on either side of the mean). Because each human brain develops uniquely, however, there are always exceptions. Some of the remaining third of the population will tend to match the generalizations even more closely, and some less closely.

If some of your personal characteristics/behaviors don’t match a specific generalization in the Practical Applications section, it doesn’t invalidate the research. It does exemplify individual uniqueness, as no two brains are ever identical in structure, function, or perception, not even the brains of identical twins. Avoid discounting first-impression mismatches too quickly, however. Perhaps you haven’t had the opportunity to hone a specific skill, or your personal past experiences have impacted you in unusual ways.