Michael has a minor in psychology & spent the last few years learning about MBTI/cognitive functions.
INFPs use introverted feeling (Fi) as their lead, or primary function and extroverted intuition (Ne) as their second, or secondary function. No other type uses these two cognitive functions in the same order. This makes for an unique combination of decision making and perceiving thought processes for INFPs.
Introverted Feeling (Fi)
As their lead cognitive function introverted feeling (Fi) works as a way for INFPs make their judgements. Introverted feeling is focused internally as a subjective value system. Thus, this internal nature of Fi helps the INFP assign value to people, objects and ideas based on their own set of standards. Which leads INFPs to gravitate towards those things, as long as they harmonize with their ideals.
Extroverted Intuition (Ne)
INFP's second leading (secondary) function is extroverted intuition (Ne). It is a perceiving function, and is primary way in which INFPs take in information. Extroverted intuition is focused outwardly and is more identifiable than the primary function of introverted feeling. As such, this is the function that others will most likely see in INFP's everyday interactions. Extroverted intuition is also divergent in usage, which means that an INFP might like abstract concepts and/or connecting unrelated ideas.
How INFPs Use Fi in Their Friendships
Introverted feeling-as the hallmark of all INFPs-is applied in friendship as an empathetic force. Because of this, friends of INFPs will become the beneficiaries of compassionate displays of caring. For instance, an INFP will always be there as an ear to listen, a shoulder to cry on or a warm body to hug. This means that they're most always putting their friend's needs before their own.
Introverted feeling also synthesizes the INFP's moral compass. Which leads to INFPs taking their friendships to heart. This comes from a desire to seek lifelong bonds because it's in their moral code to stay loyal to close friends. Of course, as long as their values are never crossed.
How INFPs Use Ne in Their Friendships
Extroverted Intuition (Ne) is manifested in INFP friendships as creative problem solving. Because Ne is divergent in nature, it's relatively easy for an INFP to see multiple vantage points of an issue. This is a relatively great asset within a friendship, because there will always be something positive that the INFP can see in the face of a problem. Whenever a friend is in need of some advice, the INFP will have an answer. And it will most certainly come from a perspective that is not easily identifiable.
The expansiveness of the Ne function is also beneficial for good conversation. Because INFPs will probably introduce friends to new things. And those things can be passionately discussed for hours. Friends may even find themselves completely enriched by the new and exciting topics that are discussed, despite how niche they may be.
The cognitive processes of Fi and Ne serve the INFP well in friendships. Because of this, friends of INFPs will always feel as though they have a caring, sincere, creative, and quirky friend at their disposal.