First of all, I don't think Keirsey's second ring and third ring are accurate.
My view is that Keirsey was mostly right, and Jung (and Aushra) were wrong. For example, SLI and SEI do not focus on their internal worlds more than ILE and IEE. All of them focus on both the external world and the internal world. But SLI's and SEI's "worlds" are more about reality, and ILE's and IEE's "worlds" are more about ideas. However, extroverted/introverted behavior is not related to this. Extroverts are more interested in the meaning of/interaction with objects than the exact definition/description (and vice versa). Therefore, extroverts are more active and spontaneous.
"Communication: Concrete vs. Abstract
First, people naturally think and talk about what they are interested in, and if you listen carefully to people's conversations, you find two broad but distinct areas of subject matter.
Some people talk primarily about the external, concrete world of everyday reality: facts and figures, work and play, home and family, news, sports and weather -- all the who-what-when-where-and how much's of life.
Other people talk primarily about the internal, abstract world of ideas: theories and conjectures, dreams and philosophies, beliefs and fantasies --all the why's, if's, and what-might-be's of life.
At times, of course, everyone addresses both sorts of topics, but in their daily lives, and for the most part, Concrete people talk about reality, while Abstract people talk about ideas."
"The fourth ring - Expressive versus Reserved (Attentive)
The fourth ring describes how people interact in with their environment. Individuals who primarily say and do before they listen and watch are described as expressive whereas people who primarily listen and watch before they say and do are described as attentive."
"Jung started describing psychological types with the directions of human psyche extraversion – introversion.
Every phenomenon in the world can be considered either from the point of view of objects or from the point of view of relationships.
So, we have divided all the information flow into two big parts:
1. information about objects;
2. information about relationships.
Information aspects about objects are called extraverted.
Information aspects about relationships are called introverted.
Both of these mechanisms are necessary for every person’s psyche. A. Augustinavichuite writes: “The necessary condition for the functioning of any organism is the double bond with the world around… For the brain functioning as an information metabolism device it should be provided for with signals both from outside and the organism itself".
Differences in the personality types are determined by the mechanism (one of these two) which is more often, customarily, surely, successfully and effectively used by the person. Let us remind of the fact that we can speak about a harmoniously developed personality when a person uses his strong and weak features almost like the proportion of golden section: approximately 60:40. That is a harmoniously developed extravert in about 60% of cases uses the mechanism of extraversion: is interested in the objects of the outer world, people, affairs etc. And about 40% of his attention is drawn to his inner world: to himself, his own attitude to the objects (people, affairs). An introvert accordingly vice versa ."