Q. The other day I was complaining to my neighbor about the noise in the house (our three sets of twins were being particularly rambunctious). My neighbor said, “Oh, are you an introvert?” I’ve heard the terms extrovert and introvert but I’m not sure what they mean. Do you have definitions?

A. The terms extrovert, ambivert, and introvert are simply labels for three differing types of brains. They refer to the types of environments in which differing brains feel most alive and alert. For example, each type or category of brains tends to feel at their most alive, switched on, energetic, and capable when they are in environments that matches the need for stimulation. For example:

• Extroverts: gravitate toward very stimulating environments in which a lot is going on. They may like people and enjoy interacting with large numbers of people or they may be prefer to obtain the stimulation their brains crave by interacting with nature, reading stimulating books, or using equipment (such as doing research or playing games on computers). This includes activities that are high excitement and sometimes high risk.

• Introverts: tend to gravitate toward quieter and relatively low-key environments where they can ponder what they have read or heard or are imagining. They may like people very much but they usually prefer interacting with a small group or with only two or three others at a time. They often like to work alone, at least for part of the time. This includes activities that are low stimulation and typically low risk but that may require high attention.

• Ambiverts: tend to prefer moderately stimulating environments. They can enjoy interacting with others and nature or equipment and then tend to back off for a while and interact with just a few individuals. It involves a type of 50:50 dance with stimulation for a while and then a break from stimulation. This includes activities that are moderate in both excitement, attention, and risk.

Remember that all human brains require sleep and rest and relaxation. Once each brain has received its optimum amount, it tends to gravitate toward the type of environment that matches its need for stimulation. There are differing estimates of the relative percentages of individuals who fall into these categories. Below is an example of one continuum.

Your preferred position on the EAI Continuum is believed to be set at birth. You can move temporarily to nonpreferred positions on the EAI Continuum based on what is required of you at any given time, but you will likely use more energy when functioning at those positions.

In which type of environment do you feel at your best—at your most alive, alert, switched on, energetic, and capable? If you have no idea, there is an EAI Assessment on my website that you can print off and complete free of charge.