don't stress, it's a lot of information to deal with all at once, and sometimes it's a bit conflicting.
we'll help you figure it out
stereotypes
a function is simply a "thinking pattern" - how your cognition tends to proceed.
common stereotypes generally arise because of how certain thinking patterns tend to be correlated with certain thoughts, feelings, or behaviors. for instance, nostalgia
is a Si stereotype because the Si process involves tapping into past experience. but there are emotional/value connotations that go along with nostalgia - fondness, longing - that don't have anything to do with using Si. Si is a
Perceiving function only - it does not attach value, like a Judgment function. it can conjure images of the past but it does not attach fondness or longing to them.
what's interesting is that, in my experience, the average INFP (with Si as their #3 function) tends to express nostalgia more often than the average SJ, probably because INFPs are strong internal feelers. my ESFJ mom, for example, is not very nostalgic, even though Si is her second function. she uses the past as a primary source of information, but her emotional investment is much more rooted in the present, in her Fe-mediated relationships with others.
XXXX "with high Xx"
there are, of course, individual differences between members of the same type, and sometimes people use the phrase "with high __" to describe that. to take your example, an ISFJ with much higher Si than Fe will be slightly different from an ISFJ with relatively equal Si and Fe. if they've typed themselves as ISFJ, they've decided that they use Si most of all, but if a person has "high Fe" what they probably mean is that their Fe usage is relatively equal to their Si usage (or at least it seems like they use it more than other ISFJs they know). that will probably make them warmer, more directive, and more social than the average ISFJ.
then let's take the INTJ with "high Fi". what can sometimes confuse people when they're figuring out their type is the 3rd (tertiary) function, which can often seem very strong. the key difference between this function and the main two is that people feel like they can turn their 3rd function "off" and "on", while the 1 and 2 feel essentially involuntary. the 3rd function is also known for being a bit "childlike" in usage - often it will seem a little immature in the way it is handled.
given the example of the INTJ, they may sometimes engage strong inner valuing, in particular to deal with situations that their Ni and Te are having trouble handling alone. but unlike an FP, who is very familiar with Fi, and understands and uses Fi in fine distinctions, the INTJ might experience Fi as somewhat clumsy and foreign, and make use of it in a way that is overwhelming to themselves and others - much in the way a child learning to write fumbles with their pencil. an INTJ with "high Fi" is generally someone whose Fi is more developed and controlled than that, and they are therefore able to engage in consistent, mature usage of it.
Ne vs Ni
N functions can be difficult to internally discern between because they are abstract, "jumpy", and often subconscious (Ni in particular). Perceiving functions are also often more difficult to decide on than Judging functions because it's easier to assess how we choose than how we
see. looking at a Perceiving function is like looking at a lens - kind of tricky when you need it to see in the first place!
so -
maybe it'll help if i try to boil things down a little? you probably already have read a lot of this, and know a lot of this, but maybe if we try to keep the information really simple it'll help get away from the stereotypes.
functions
the
only thing you need to do to know your type is to figure out the 2 main functions that you use.
i've listed the functions in two sets below - the Perceiving (N/S) and Judging (T/F). try to choose the one that sounds the most like how you think from each one of the two sets. one of your choices will need to be introverted and the other extraverted, so choose what sounds like the best i/e pair.
if you feel like both two introverted or two extraverted functions describe you the best, then try choosing which one between the two you use
most, and then consider the other one as a #3, and choose a different #2. for example, if you like both Ni and Ti, then you could consider INFJ, who uses Ni Fe Ti, or ISTP - Ti Se Ni. or if you like Si and Fi, INFP - Fi Ne Si or ISTJ - Si Te Fi.
Perceiving functions: S and N - Se, Si, Ne, Ni
the Perceiving functions describe how you look at information. the two main categories of how to look at information are Sensing and iNtuitive - whether you tend to focus more on
what it is (S) or
what it could be (N).
- an extraverted Sensor will focus on what is outside themselves, concentrating on the concrete (often physical) data around them in the present moment. they are good at quickly responding to external concrete stimuli - sounds, sights, smells, tastes, feelings, touch.
- an introverted Sensor will regularly access an internal database of concrete information ("facts") in their mind, that they have gathered over time. they are good at linking present sensation-knowledge to past sensation-knowledge. they utilize what is commonly called "experiential learning" - wisdom through experience.
- an extraverted iNtuiter will focus on what is outside themselves, concentrating on the ever-expanding associations that are triggered in the present moment. they are good at quickly linking external abstract stimuli - concepts, ideas, symbols, patterns. "everything is connected."
- an introverted iNtuiter will regularly access an (often subconscious) internal database of intuitions in their mind, that they have gathered over time. they are good at linking present abstract data - connections and patterns - to universal concepts, and thereby predicting future events. Ni is probably the hardest P function to describe. it's commonly associated with "aha!" moments in thinking and a compelling future "vision".
Judging functions: T and F - Te, Ti, Fe, Fi
the two Judging processes describe how you prioritize information. Thinkers use logic, while Feelers use personal valuing.
- an extraverted Thinker organizes their external environment based on empirical rationality. they are attuned to how to direct people and monitor systems for best efficiency and productivity.
- an introverted Thinker is primarily concerned with the internal logic of systems. they are attuned to precision, accuracy, and refinement. they focus on the internal mechanics of how things work, and how to improve them.
- an extraverted Feeler is highly aware of interpersonal relationships and adept at creating harmony between and amongst people. they know how to motivate and manage others for greater good, and are attuned to social climates and currents.
- an introverted Feeler is concerned with the "inner wellbeing" of individuals and internal consistency of identity. they are attuned to values, ethics, and emotional nuance. Fi is probably the hardest J function to describe. some writers describe it as internal "Feeling tones". it is often expressed in emotional terms but is a more complex sort of overall visceral experience.
order
once you've narrowed down to two functions, you can decide which one is first. the #1 will be a "leading" function - it will be present in almost everything you do and will motivate a lot of your moment-to-moment choices. sometimes it's surprising to realize how much you use it - i used to think i was an INFP before i realized how much i use Ne. i just thought everyone thought like that!
a helpful trick - psychologist John Beebe described the functions in order as taking on specific roles. he calls the #1 function the Hero, the "star" of your story. the #2 function is a "guiding" function, helping you relate to others and assisting your first function when it has a problem to solve. Beebe calls its role the "Supportive Parent".
once you think you've got it figured out, then you can peruse some type descriptions and see if they seem to fit. there are always going to be some things that don't quite seem right - personally i shied away from ever even considering ENFP before learning about the functions because i'm pretty quiet IRL and type profiles often made ENFPs sound really loud.
you're welcome to post the ones you chose and tell us if they feel right - or if not, why they don't. then we can try to help you more from there