http://www.the16types.info/vbulletin...-of-the-Psyche
Inert and contact
Inert functions (1, 4, 6, 7) are those that do not integrate information from the environment; thus, the strength of these functions remain the way they are. A person does not seek guidance in these areas as they comprise the core of their natural strengths and weaknesses.
Inert functions 1 and 4 are a part of the mental ring; these are essentially one's most confident strengths (base function) and debilitating weaknesses (point of least resistance). It is for this reason that strong judgments about these aspects of reality are inadvertently made.
Inert functions 6 and 7 are in the vital ring of a person's psyche. An individual is hardly aware of how these functions are used. The mobilizing function is inert since its primary mechanism is to mobilize one's creative function into action. Thus one's ability to use it does not become much stronger throughout life. The ignoring function is inert because it is part of a person's natural strength, just like the base function. Conscious information is limited here in favor of the leading function.
Contact functions (2, 3, 5, 8) are essentially how we touch upon the environment; they adapt and integrate new experiences from the environment. These are capable of being improved over time (through ability or simply new understandings).
Contact functions 2 and 3 are in the mental ring. The creative function produces new information out of what is accepted by the base function. This is literally how we uniquely 'make contact' with the world. This has potential to grow stronger as a conscious element since it's the Ego's connection to reality. In the role function, however, information from the environment is weakly accepted situationally, and is subdued since it opposes the base function's approach. Although it cannot truly grow in strength, where it does grow is within the individual's subjective understanding of that aspect of reality.
Contact functions 5 and 8 are in the vital ring and strive to unconsciously make contact with the environment. This is indefinitely true of the suggestive function. Since it complements the base function, people unknowingly seek information related to it from the environment to strengthen its ability.
It is theoretically the only way one can improve on their leading function. The demonstrative function makes contact with one's environment very unconsciously; it acts with the conscious leading function to produce one's unique worldview, being just as strong as the base function.