Guest post by, “you only live once but living once means living many times ,as a series of similar but technically different people who know each other in one direction but who can help each other but only in the other direction,” ENTP
The Big Bang Theory
Introverted Sensing (Si): Introverted Sensing deals primarily with recalling facts and details of past events. Sheldon has an eidetic memory. Introverted Sensing is very tradition and ritual oriented. Sheldon holds on to these traditions very closely. In the series often Leonard and Howard often convince him to do many things just by saying its a ‘social custom’. He tends to know all the facts and enjoys system and order.He says that he does not like change and thinks that change never good,this is mostly where I believe that he is not an NT and more of an SJ. Sheldon sometimes become stubborn and refuses to try new experiences.
Extroverted Thinking (Te): Sheldon has a natural desire to control, manage and organize the world around him. His quick logical conclusions and his love of logic and an urge to be like Spock are a proof of it.He loves correcting people and pointing out a better solution,keeping feelings aside.
Introverted Feeling (Fi): Sheldon has a good talent at hiding his feelings. Keeping feelings suppressed 99.99% of his life, it is obvious that when he expresses them they are pretty intense.
Extraverted Intuition (Ne): Sheldon often jumps to conclusions about people and situations and assumes the worst possibility as fact (catastrophising). Being one of the least developed function in his personality, we only see Ne play positively when Sheldon has a big new idea (for instance: that ‘a rapidly turning mirror could turn real photons into virtual ones and vice versa’).
The Book Addict's Guide to MBTI: 
There is one big flaw in this:
ISTP is NOT Si dominant, ISTP is Se dominant. That’s a huge mistake that can affect your logic.
Sheldon is not ISTP. No way in heck.
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woops misread ISTJ for ISTP. How can I delete ma comment?
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Glad to read a better estimate of his type – when I clicked on a character mbti breakdown off of pinterest, they said he is INTP, which I could have been tickled pink over because I love that character, but I am an INTP and knew several things that were off about that. I wonder if it has to do with the impression that he gives of having Asperger’s. I admit that I rarely know why people get so out of sorts all the time, and my mom is convinced I’m on the spectrum, but I just disagree.
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I kind of agree with you,Liz. As he was raised with siblings who had below average intelligence,it may have filled him with a big ego,and once you acquire such an ego,it is difficult to let it go especially when you are actually smarter than most.But he just refuses to acknowledge the fact that there are people much smarter.He just refuses to believe that someone could be actually smarter than him because he learnt so in his childhood.
ISTJs rarely discard a belief that they learned in their childhood.
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Don’t know that I would necessarily agree that ISTJs rarely discard beliefs they learn in their childhood – however, your other points are excellent.
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I would say its probably more difficult for them to let things go once they have come to conclusions, but not impossible for a mature ISTJ, or a mature person no matter there personality type.
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Whenever I watched the show, there was always something that seemed to further prove that he is an ISTJ. It is difficult to detect the Intuition in him. My personal opinion is that he may be an example of an unhealthy ISTJ.
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Unhealthy? Jury’s out on that one for me. But I think he’s definitely autistic, and probably has OCD as well.
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Yes he is an immature ISTJ. That kind-of proves that intelligence isn’t everything.
Even after typing him as an ISTJ ,I still think that he is an Ambivert,with a bit of an OCD problem and/or asperger.
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I do believe that possible Asperger’s and OCD play a role. I used unhealthy because his FiNe is somewhat underdeveloped and SiTe emphasis is larger than in some adult ISTJs who may have more balanced functions.
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The writers themselves have said on different occasion that Sheldon does not have Autism or Asperger.
So this leads me to believe he is just an immature ISTJ, who has lived by the notion that he is the smartest person in the room, while that may be true it has stunted his growth as a person. I haven’t watched the alter season, I am behind in this show, from what I have heard he has grown as a character but still not completely mature.
Just my two cents.
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I just didn’t feel qualified to make that assessment, because I don’t have much experience with MBTI yet.
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