Okay so I made a main post about why its difficult to type anybody, and that covers a lot of the main points, but now I want to get specific to INTPs, since I am one, and I confidently mistyped myself for so long.
Somehow, we manage to really elude people's understanding, especially us female ones, so I'll also address some gender differences. Feel free to just scroll to the parts that interest you.
INTPs and the J/P Scale ::: ENTPs who think they are INTPs/INTPs expected to be ENTPs or ISFJs
I'm pretty sure a lot of INTPs get mistyped as other things in both real life and fiction, but we're out there more than people realize. Our stereotype seems to be a combination of the ISFJ and the ENTP, because people overlook a simple fact: we are dominant judgers. We're actually pretty serious, and structured, even if this structure isn't applied to the outside world. In fact, it is that simple fact that makes live so damned hard for IxxPs in general. Our sense of structure is internal, and so we need to order most aspects of our internal lives to suit our own personal methods. Having our introverted judging function as our dominant function means that this is the very most important thing to us, but of course the external world does not bend to our will, and often won't leave us alone in general. This can make us kind of cynical, actually, and no matter how friendly we seem on the surface, it is easy to upset this balance.
An easy way to tell INTP vs ENTP is that most INTPs have absolutely no doubt they are introverts. ENTPs are the ones who are closer to the I/E line.
Female INTPs ::: INTPs expected to be INFPs or ISFJs
WE EXIST. Maybe not in fiction, but we're here in real life! I promise! People type Luna Lovegood as an INTP, I guess, but I'm not too sure about that. Anyway. Because we're so rare and unassuming, though, people get mad when they realize we aren't ISFJs or INFPs. Although female INFPs don't seem to be any better liked than we are (<3 kindred spirits), they are indeed more expected than female INTPs. They also show up in movies and TV shows a lot more. But that is beside the point.
Basically, people think we should be feelers. When we get dramatic or frustrated, then we become INFPs in everyone's eyes. When we are good, people notice the functions and expect us to behave like SFJs. Little Snow Whites and such. But we aren't. So when we act out against that Fe because we're tired and want to be left alone, it is decided that we are bitches. When guys behave the same way, it is just "boys being boys". I'm not a modern feminist or anything, but I definitely get frustrated at certain expectations placed on gender roles. We can't even be "one of the guys" because we lack the Se - we're in our heads. So as much as I love INFPs and ISFJs, I am not one of them and would like to be respected for my thinks, and not have so much feeliness expected of me. </rant>
INTP Emotions ::: INTP vs INFP
INTPs can get emotional too. It is just our weakness. We definitely experience them on a daily basis, and they do in fact affect us, though being inferior AND Fe, we don't really connect to them very well. As a writer, its easier for me to explain sensory detail, thought processes, and sterile action than to explain how anyone feels deep down. At least not without feeling corny about it. An INFP would be less likely to explain logical planning and plotting, and far better at the internal feels. It can be hard to tell either type apart, on occasion though, because the Fe and Te of each type ought to have similar placings.
A few ways to tell us apart:
-INFPs speak their mind more than INTPs
-INTPs use their internal sense of logic and order to create their moral perspective. INFPs use their internal sense of what is right and wrong to help them develop a sense of order. I think. I'm not an INFP so its a little hard for me to get Fi.
-INFPs wear their "drama" on their sleeve. INTPs internalize it/don't realize it, until they have a massive outburst of frustration, as could be seen in the new Star Trek series with Spock (new Spock is an INTP - old Spock was an INTJ).
-INTPs expect society to be socially accepting of their own personal brand of logic, while INFPs expect society to be ordered to accept their own personal brand of values.
Both types can be very creative, and get excited about ideas. Neither likes getting out much on average and typically does so out of obligation. The outside world severely interferes with our internal structure.
Te on the INTP ::: INTPs Mistyped as INTJs
INTPs are actually very prone to use their Te, especially males. I find it so depressing that one of our token fanable INTPs, Dr. Gregory House, is so often mistyped as an INTJ. He is an INTP, through and through. There's no way that man uses tertiary Fi. He's just one example however. INTPs can actually be extremely J-ish, if given the chance, and if encouraged, we will learn to speak our minds (Te). When we are able to structure things to our liking, as Ti enjoys doing, we can become rather organized in many ways, and very confident, even if unfriendly. INTPs prefer this side of themselves, actually. When we use it in conjunction with our Ti, it means we are able to stand up for ourselves better, and not get quite as pushed around by social expectations as we would otherwise, and therefore are able to accomplish more and from there, be better respected.
I think a lot of guys mistype themselves as INTJs because they are able to be structured and organized more than the average, socially frustrated INTP.
The easiest way to tell an INTJ and an INTP apart is to determine whether the preference is for Si or Fi. One should be easily identified, while the other more or less shunned.
Intuition on the ISTP ::: ISTPs Mistyped as INTPs
ISTPs are commonly mistaken for INTPs. This seems to be pretty prevalent in fiction, where everyone is grasping around to find their token INTP computer geek in the story, but honestly: INTPs seem to get bored of computers, actually. I've met more S-type programmers than Ns. Once an INTP has solved how the programming works, we're done and ready to move on, unless we need it for some more abstract project or puzzle. And then it is a tool, not an interest. INTPs are also very big-picture oriented. We get our ideas, and then the details are just a means to create the larger idea we already have. ISTPs are more likely to just start doing it.
ISTPs can also mistype themselves as INTPs due to their overuse of Ni, but Ni is a more directed and focused function than Ne, and of course for them it really is overshadowed by Se, even if the user forgets to indulge in their Se. For example, an ISTP scientist will value kinesthetic work, in which they get to touch and especially DO something in the field, or something tangible. INTPs prefer to work with the intangible, and theoretical ideas. Touching things is nice, but we'd rather be wherever is most comfortable and least distracting so we can go mad-scientist on whatever it is we are trying to accomplish. INTPs also look a lot more random than ISTPs, to everyone who isn't an NP (it'd be harder for a fellow NP to recognize the randomness ;P)
Male INFJs thinking they are INTPs ::: Female INTPs thinking they are INFJs
This is the trap I fell into. Partly due to HSP, but I'll address the main part of this mistype now. INFJs and INTPs have a lot in common. Functionally, we are the only introverted Ns that use Fe/Ti. We are often considered good relationship matches.
Lets start with the boys. INFJs are already prone to delve deep into their tertiary function, Ti. It seems, in fact that Ti and Ni have an affinity for each other, causing one to seek out the other if possible. This can create a rather scientific feel on an INFJ, despite them being auxiliary Fe users. Because females tend to use more feels and males tend to use more thinks, it is easy for a male INFJ to think he might be an INTP. He feels he is analytical enough, and although he might come off as serious toward others, inwardly, he feels as though he relates to the INTPs supposed sense of humor that is often described. Being a dominant Ni user, he relates well to Ne, also.
Now for the girls. INTPs tend to take life more seriously than people generally expect, especially females who do not feel recognized for their prowess of the brain and might feel as though they have something to prove. In this way, we relate to the serious undertones of the INFJ description, and might even resonate with their relationship to Fe. Mistaking Ti for Ni, we might pursue this route, wondering why everyone thinks we are rude, when we feel as though we ought to be coming off as wise. We don't entirely relate to the other INFJs and their fluffy-cuddly-feely posts, but maybe we're just in better touch with our tertiary Ti. But that is not the case, O Female INTP. You'd have to be quite the evil INFJ to think of something that rude to say.
An easy way to tell between an INFJ and an INTP is whether the user recognizes Si.
Another note: Ne users connect faster to others over shared ideas; Se users connect faster to others by shared activities. Over time, Ne users tap into their Si and wish to have shared activities while Se users over time would tap into their Ni and care more about shared ideas, though the Ne still prioritizes ideas over activity and Se the other way around. Js will make this switch faster and more strongly than Ps.
Heartless INTPs ::: Our ENTJ Shadow
Contrary to the goofy exterior everyone thinks we also have underneath, we're actually kind of similar to ENTJs in several ways. ENTJs are our shadows. This means, we share none of the same functions. INTP functions are like this:
And then ENTJ:
Because of this, we are very different, but note that all of the functions are in the same order:
So we may or may not feel similar to the ENTJ, but if anything, we get along quite well with them. I surprised everyone I knew in college by marrying one, even though I'm pretty sure I looked like... something else. Certainly not inferior feels. Anyway, some INTPs can behave simiilarly as well. This is because when looking at dominant functions, the INTP will understand Te very well, while the ENTJ will understand Ti really well.
The main note I'd like to make here, however, is this: ENTJs are harsh on the outside (Te) but mushy on the inside (Fi). INTPs are squishy and fun on the outside (Fe) but can be very cold and hard on the inside (Ti). But we still have feels. I promise. It is just a lot harder to bring them out than it is on the ENTJ, because we don't even notice them half the time.
HSP on an INTP
INTPs are not commonly known to be HSPs, but just because it made such a huge difference for me, I feel like I should address it. HSP means "Highly Sensitive Person" and refers to a phenomenon in which certain people receive too much sensory stimuli. It is said to affect approximately 15-20% of the population, and about 70% of those are introverts, but most of them seem to be INFxs.
How HSP affected me as an INTP:
-Increased Si ~ I seem to have really oddly high Si sometimes. Like, other INTPs seem to enjoy atmospheres, but I'm so particular about creating them that I go on cleaning frenzies once or twice a month so I can arrange my house/room to have a specific atmosphere I like. If I could, I'd be able to rearrange it between various sci-fi, fantasy and cultural feels, but I can't because that would require money. So it remains slightly multicultural/fantasy and cozy because I need that cozy more than I need the sci-fi.
-Seemingly Increased Fe ~ I can tell that my Fe isn't that good still, but I *seem* to have it well-developed from my perspective. Anyone who knows me well would know that isn't true, but I thought it was for quite some time, hah. I have a lot of empathy for people to the point where I almost can be NF-Idealist about it and I can get up-in-arms about injustice. HSP makes it so that I don't have to actually experience something physically to experience it emotionally. However, I still put logic, efficiency above harmony in regards to priorities and thus it is easy to tell I'm actually inferior feels. I do happen to act on harmony more often than logic or efficiency however, because it is simply easier and I tire quickly.
-Hypochondria ~ I sometimes end up running through a million reasons (Ne) why I might be sick from something because of some little detail of my body that drives me insane. HSP increases one's bodily awareness, which Si did already as well. Worse yet, tert Si users aren't very good at taking care of themselves, so I have trouble drinking enough water, getting enough sleep, eating appropriate types and amounts of foods (sometimes I'll eat too little and other times too much), so I often think maybe I caused a problem myself. Now that I can logically deduce I'm overreacting, its not so bad, but when I get stressed out it can take over.
-Hyper-Introversion ~ I'm not actually any more introverted than the next INTP, but I have more trouble being out of my house because people disturb my required peace intake for the day :[ I need darker, quieter, calmer atmospheres than most. What is just a bright light to one person, is a supernova in my face. What is just a loud noise to someone, is nails on a chalkboard. What is just background noise is a cacophony to me. I need to have my space to recollect and recharge before having to get back out. I'd be happy to not leave my house for more than 4 hours a day, and then I could maybe tack on 2 hours worth of socialization at my house (but not over the phone - I despise phones). I also suck at multitasking. I'm supposed to be good at it because I'm a girl, but I'm not. I'm just not. I hate multitasking. It is extraordinarily overwhelming, particularly social multitasking. If I'm not being forced to respond to anything, then fine, but otherwise I need to be left alone to complete a task.
-HSP Differences ~ I don't fit the HSP description perfectly, and many of us won't. Here are my differences.
>HSPs are supposed to also be more attuned to their surroundings due to the stimulation, and I am in certain ways, but overall not really. Like I said in regards to hyper-introversion, I do seem to hear/taste/see things more strongly, but I don't really notice the minute details of the room all that quickly. Or if I do, I don't say anything and forget that I did. But, INTPs have almost no Se, so that wouldn't exactly make the strongest impression either.
>HSPs are supposed to have trouble with violence. I'm not too crazy about action movies, but mainly because of the noise and I tend to zone out and have trouble keeping up with the plot, and then the INTP issue of it simply not being that engaging to me compared to something more cerebral. I do have issues with guts. I hate seeing or even thinking about guts being removed from one's body. But blood doesn't bother me, nor even impalement. Its more the removal of parts of the body that should remain there.
>I don't avoid emotionally engaging things. I seek them out. HSPs typically avoid it because it makes them upset. I'm still trying to figure out why I like things that make me upset, but I do. Sometimes I'm even relieved after fighting with a friend. Its very strange. I just channel it into a story I'm going to write, and I am suddenly at home.
>I've never noticed a correlation between caffeine and my body at all. It does seem to make me move physically faster, but not mentally. HSPs are supposed to be strongly affected by caffeine. I don't seem to be affected much at all.