The often misunderstood terms extrovert and introvert derive from this work. In Jung's original usage, the extrovert orientation finds meaning outside the self, in the surrounding world, whereas the introvert is introspective and finds it within. Jung also identified four primary modes of experiencing the world: thought, feeling, sensation, and intuition. (He referred to these as the four functions.) Broadly speaking, we tend to work from our most developed function, while we need to widen our personality by developing the others. Related to this, Jung noted that the unconscious often tends to reveal itself most easily through a person's least developed function. The encounter with the unconscious and development of the inferior function(s) thus tend to progress together.

Significant in Jung's theory is that "type preferences" are inborn and not socially constructed through interaction with the parents, family, culture and other external influences. While this is true, the individual is impacted in the quality and strength of the development in her or his preferences. Nature and nurture are both at play. A supportive environment will support and facilitate inborn preference development; a contrary environment will impede or retard the natural development of inborn preferences. The research on the mental health problems of many left-handed children forced to be right-handed is not dissimilar to what often occurs for people "forced" into a non-preferred mode of personal orientation.

In the field of family systems theory, psychological type holds potential as another way to understand the internal conflicts and alliances within the family. Parents can often be seen to have concern about children who operate from type preferences different from theirs and run the risk of encouraging, and at times coercing, children into a false personality. As a child resists or naturally fails to adhere to the parental guidance, conflict readily occurs. "Type-alike" family members will naturally gravitate toward each other. The best approach is to try to identify type preferences of all family members and to actively encourage those preferences, while training children, as well, in non-preferred functions.

Psychological Types – another view:

Imagine a person (the subject) observing an object or event. For example, a house that they are considering buying. The introvert relates more to the subject – what would this house, as a home, do for their life experience? The extravert relates more to the object – the house. What could be done with this particular building? The focus being on the building itself.

There are four psychological functions in Jung’s model: two rational functions (thinking and feeling), and two perceptive functions (sensation and intuition).

Sensation is the perception of facts. In our example, suppose the house is well built, it has a large garden, it is two miles from the shops, and the buyer has a nervous tic when he/she mentions money.

Intuition is the perception of the unseen. For example, the seller is hiding something, I’d be content here for the next twenty years.

Thinking is analytical, deductive cognition. For example, compared to the house I viewed yesterday, this is overpriced, bigger, nearer to work, overall it would cost so much per month more on my mortgage, but I’d spend two hours less travelling each week.

Feeling is synthetic, all-inclusive cognition. For example "I’ll have to sleep on it before I know whether this house could be home. Even then I may not know!" Feeling takes time. The feeling function is not the same as emotion, which Jungian psychology refers to as affect (emphasising its physiological component) but the feeling function and affect (emotion) clearly do influence each other.

In any person, the degree of introversion/extraversion of one function can be quite different to that of another function. For example extraverted intuition— imagining endless means of political change; with relatively introverted thinking— "How would I fit into such a society?"

Introverted intuitives tend to be weak at extraverted sensation (and vice versa)— they have very good insight into themselves, their unseen motives and likely long term goals, but can’t find their adjustable spanner nine times out ten. Intuition is often inspired, and other times completely wrong. It has to be checked with one of the rational functions, thinking or feeling. Introverted thinking types tend to be weak at extraverted feeling.

Note. As for training children, while it is a good thing to appreciate the psychological type of a child, or indeed of anyone (it is also very rarely practised), it is most productive to understand the psychological typology of children – then leave them alone. ‘Leading’ anyone into their inferior function can be dangerous. Though it has its uses for mature analysands with the assistance of an experienced therapist, it is not part of the educational or parental role. If a child has suppressed feeling, for example, it may be a survival strategy.