Each personality type has four Cognitive Functions. Functions put language to the way they process information and make decisions, and their order is based on personal preferences. Thinking and Feeling are used to make decisions, while iNtuition and Sensing are used to process information. Each type is referred to by their top two functions. Internal functions are the ones you use in your head, and external functions are the ones you use to interact with the world around you.

The TiNe’s functions are as follows:
1. Ti - internal Thinking
TiNe's use Ti to make decisions based on logical analysis done over time in their heads. Ti is the reason they prize rationality and objectivity. It also drives their insatiable thirst for knowledge and learning. Because it is their strongest preference, the functions below are said to "serve" the Ti. This just means that the Ti way of doing things gets priority most of the time. 

2. Ne - external iNtuition
Ne is the main way TiNe’s take in information. It means they use their intuition to find patterns, underlying principles, and ideas, to construct theories and frameworks, and to form connections as they talk, write, or create. It can make them seem quite "rambley" at times as they can jump from topic to topic based on the connections they're making in the moment rather than following a more linear path of conversation.

3. Si - internal Sensing
Si is the TiNe’s third function, and it allows them to store all the interesting facts and knowledge they gather in their brain in an organized way for future reference. Si also makes the Ti-led internal world fairly structured and detailed in its analysis, and can often lead to a very strong sense of internal stability which can come across as arrogance to others. While they can jump from topic to topic in conversation, internally their thought patterns are more linear. For TiNe's in particular, their Si drives them to have a high need for precise language, and they can often articulate themselves very well when they want to. As they get older, their thought processes get faster. After some time they will likely not need to consciously think through every step in a thought process unless they're taking on a very novel problem or task.

4. Fe - external Feeling
Fe is the TiNe’s last function. As a last function, it is inherently not as strong as the other functions and the TiNe generally prefers to only use it where necessary, rather than using to make all their decisions. Fe is the TiNe’s humanitarian side. It causes them to want to use their intelligence and creative problem-solving to help others and fix the world in some way. Having Fe last means that TiNe’s often start out life being less aware of and equipped to deal with feelings than other types. Even though it's last, a healthy TiNe will learn to develop all of their functions over time so they can use them as needed.

Internal World

Ti is the function which best lends itself to in-depth logical analysis. It is primarily concerned with solving problems and finding answers, and often prides itself in its ability to be detached from situations in order to be as objective as possible. Ti types are more likely than others to be able to literally shut out emotions and bodily sensations in order to enjoy objectivity. They often do this when problem-solving, meeting a new person, starting a new activity, or arguing using reason.

Ti is primarily concerned with learning. Not just gaining knowledge, but understanding complex things in a deep way. TiNe’s see the possibilities available using Ne, pick things apart into their smallest components so that each detail can be stored using Si, and then apply this information across a variety of situations using Ne.

Ti differs from Te (external Thinking) in that it doesn’t make near-instantaneous executive decisions. It needs time (could be days, weeks, or decades depending on how complex the topic is) to fully understand things and make decisions about them. This is because Ti-dominant types have a need to explore something in-depth before they feel comfortable coming to a conclusion about it. TiNe's need to withdraw from the world often in order to process all of their observations. They often spend a significant amount of time searching for cognitive biases within themselves so they can remove them and therefore be more objective in their analyses.

Every Ti-dominant person grows at their own pace, and being Ti doesn't guarantee that you're a genius, but at some level, nearly every Ti-dom has an impatience for stupidity. More mature Ti-doms have usually altered their personal definition of stupidity at least a handful of times throughout their life to allow grace and understanding for those who are inherently different from them. This differs from immature Ti, which commonly regards those who can’t operate in a strong Ti-driven way as simply inferior. Unsurprisingly, this kind of attitude usually comes across as arrogance to others.

In preliminary neuroscience findings by Dario Nardi, Ph.D., strong Ti is correlated with being able to do multiple types of analysis at once. TiNe’s primarily use Deduction and Categorization:

"Deduction - Linearly deriving solutions using verbal/symbolic reasoning. For example, if A=B, and B=C, then A=C. Using this region is like moving along the branches of a tree.

Categorizing - Categorizing and defining concepts in a holistic way using a “best-fit” process. For example, it helps us determine whether a dolphin better fits in the mammal or fish category as it sorts many categories simultaneously."

They also make some use of Odds Assessment, though not nearly as heavily:

"Odds Assessment - Holistically weighing numerous pros and cons of many uncertain or risky factors or opinions at once to arrive at a single result. For example, how are the odds when you play a particular betting game?"

When discussing complex ideas, or participating in a debate, TiNe’s types can quickly engage all three regions above, as well as both core processing regions:

• The first provides reasons for things, decides between options, and detects errors...
• While the other keeps track of where in the process of thinking they are.

Ti paired with Si can be especially calculating, or even cold at times. Together Ti and Si form a library of knowledge. This library is regularly accessed and processed in a way that reflects classic critical thinking and programming languages. It sees things as being made up of billions of simple binaries: 1 or 0, correct or incorrect, true or false.

This natural skill for logic is why a TiNe can feel uncomfortable with other types claiming to be rational. Rationality is TiNe’s “thing”, and they like when it’s recognized and appreciated. This doesn’t mean they’re always right, but you can be damn well sure that if they make a claim, they’ve likely done extensive research to back it up.

Si allows TiNe’s to compartmentalize and divide up the data they gather into segments and boxes based on the topics the data is relevant to. Si enjoys having data that is broken down into its smallest, most simplified parts. Because Ti decides what is interesting or important and what’s not, all the irrelevant details that are no longer needed can be let go of and forgotten, while the useful data is saved for later.

This can carry over into the TiNe’s personal life, meaning that even the people they know get broken down into pieces of information. It’s important that the TiNe has and makes use of their Fe in relationships to ensure that they don’t simply become cold and analytical of the people they love. An example of this: Because Ti types can gather the key points of what someone is saying very quickly, and Si stores away any pertinent data as soon as it hears it, TiNe types may simply stop listening after they feel they understand what the other person is saying. However, actually listening even after the core information seems to be gathered can be far more beneficial to the relationship as it makes the other person feel good.

External World

Generally speaking, Ti operates over time, privately, in one’s head. It uses Ne to take in all sorts of observations and then has Si store anything interesting so that Ti can reference it later. The Ti/Si library of knowledge is available for the Ne at any moment so it can take 10-100 pieces of information to compose a principle, framework, idea or thought.

Ne prefers to learn as much as it can from others experiences in order to make fewer mistakes and to not waste time reinventing the wheel. Ne wants to do something new, so it has to keep a close watch on what’s already been done. Ne is abstract and oriented towards theories, patterns, frameworks, and principles. This drives Si to fit the data it gathers into theories and principles that the TiNe can use to understand the world better.

TiNe’s have a world of theories that are swirling around at any given time, and it’s important for them to have time alone in order to develop them. Their best ideas will usually come when they have a sense of inner peace and enough input. Many TiNe’s find mindfulness, meditation, or another form of intentional relaxation to be useful for obtaining peace. As far as input goes, learning interestings things or having an intellectual conversation with someone are safe bets.

For the ideas that have had some time to percolate, the TiNe needs to have places for output. Whether it’s writing, speaking, teaching, building, designing, or something else, it’s important to have space to string together the things they’ve studied in a unique way. This can also help them to refine and perfect the expression of their ideas. While they may feel like they understand something fully in their head, and they often make great teachers, they may not be as adept at explaining things to others without previous practice.

Ne loves novelty. It is always looking for a new shiny puzzle to solve or a new thing to learn about. Because Ne can get easily bored with something after reaching a basic level of competence, many TiNe’s end up becoming polymaths. However, they often have one or two things that remain as a thread throughout their lives - the couple things they have never found boring. It’s likely they will eventually become an expert in these areas if they don’t lapse for too long in their study or practice of them.

Ne is all about ideas, possibilities, and the future. It is less about what is or the current moment. This can make it tough for TiNe’s to savour the moment and to celebrate their successes. Their Ne means they are always able to see what they need to do next and their Ti and Si show them what they could have done better.

Because TiNe’s have Si as their third function, many of them struggle with some level of sensory overload. Although they can put up their walls and detach from the outside world more than most, things like excessively loud or bright environments or uncomfortable clothes can put them over the edge. As the TiNe’s last function is their Fe (external Feeling), environments that are charged with a lot of emotion or full of people can also be highly stressful.

Fe, the TiNe’s last function, can be their biggest challenge and achilles heel. Prizing objective logic and rational analysis above all means that their relationships can suffer without a lot of intentional effort put into developing this side of them. Fe is altruistic and is satisfied when it can care for others in meaningful ways. Being Fe sometimes means that TiNe’s can struggle to say no when asked for help by someone they love.

Ne can also pair with Fe to help the TiNe adapt to each moment. Ti and Si keep track of the data they collect in social interaction, and Ne and Fe pulls on that data to follow and act on the patterns they observe as far as what is deemed acceptable and appropriate. TiNe’s can be so good at this that they are commonly deemed Chameleons. The danger in this is that the TiNe can adapt so well to others that they are not able to be themselves. This makes it a huge relief for TiNe’s to find other TiNe’s or NeTi’s to hang out with, as they can set aside all the “normal” expected social behaviours in each others company.

Some TiNe’s can be prone to get into debates because they like to question what other people think in order to deepen their understanding and get to the heart of matters. Those who like it usually debate in order to work through their own ideas and refine their understand of the topic by taking it outside their heads and into the real world. TiNe’s also often play devil’s advocate, even against their own ideas, and they are just as likely to be trying to convince themselves of their argument as they are trying to convince the other person. It can be frustrating to a TiNe when the other person in an argument keeps trying to dodge the questions and avoid the topic. Some TiNe’s may find any kind of debate uncomfortable and will avoid it as much as possible as it’s just not worth dealing with the other person getting emotional.

TiNe’s more generally find themselves asking people lots of questions and engaging in less argumentative types of discourse in order to gather data, build upon ideas and concepts, and if it’s someone they care about and desire relationship with - analyze them in order to figure out how to best connect with them. Because the TiNe’s Fe is last, they might not notice in the moment that not everyone appreciates being analyzed.

Interestingly enough, TiNe’s tend to not have much respect for most social traditions and rules unless they see a valid purpose behind them. They hate the fact that to be acceptable in society, one must dance around stating the facts or go to great lengths to dress and act the part. Part of this comes from feeling like they are lying about who they are in order to meet people’s expectations. The other part comes from the fact that although TiNe’s can adapt to almost any situation, their low Fe means they sometimes offend people and don’t even realize it until later, if at all.

Their lack of interest in adhering to social norms and love of logic should not be interpreted to mean that they do not care about other people in their lives. They simply show that they care in a straightforward, problem-solving way. Many TiNe’s do care deeply about social issues and the welfare of their communities, and generally desire to live at peace with everyone around them if possible. They just don’t usually have the emotional stamina to be “touchy feely” with more than a handful of people who are close to them.

Fe is the function that helps TiNe’s process their feelings and respond to the feelings of others. Because it can take the longest to develop, TiNe’s might make some messes in their early years that they can’t fully comprehend until they grow older. Generally speaking, females TiNe’s seem to develop their Fe faster than males. This makes sense in the context of gender roles and expectations from parents, peers, and general society, but also in the context of friendships. Females in their childhood typically draw other females as friends. Because most females are more into their feelings, the female TiNe may have to figure out quite quickly how to adapt and respond appropriately when a friend is having a bad day, or when there is a breakdown in communication in the relationship. Male TiNe’s on the other hand may not have the same pressure from their parents and friends to be empathetic the way females are expected to be.

For the TiNe themselves, their experiences with emotion in childhood can be a little scary. Their emotions are typically expressed as a sudden, in-the-moment way, and they can be very hard to pin down. They don’t have a deep well of feelings inside that they’re constantly attending to and processing (like Fi - internal Feeling types do). Some TiNe’s have described deeply embarrassing moments where they burst into tears in their classroom and couldn’t explain why. When everyone is staring at you and asking for the reasoning behind how you feel instead of giving you time to think through what’s going on, it can lead to even more negative feelings in the moment.

As an adult, healthy TiNe’s develop ways to determine what their feelings are and process them properly. Two key stages in this process are becoming comfortable with not understanding every emotion and finding a safe way to express emotion as soon as possible so it doesn’t get stuffed away in the closet. It can be tempting for TiNe’s to think that every emotion has a deep meaning behind it. Unsurprisingly, they see emotions as more data to work with. TiNe’s thought process might go something like this: “Ah, I am experiencing pain. How can I never experience that again? I must analyze my feelings from every angle to discover how to obtain immunity from this unpleasant experience in the future.”

Unfortunately, this can lead to them taking all their feelings inside to pick them apart instead of just letting them be. Trying to analyze it in the moment is a bit like trying to drive to the store to get painkillers when you have a killer migraine - it’s incredibly frustrating and debilitating to try and fix the problem when you’re in the middle of it. What seems to be much healthier is for the TiNe to give up the right to understand every emotion to its depths, and instead simply express it and let it go. Often, they’ll find that they get more accurate insights into things after the emotion has passed.

TiNe’s can also struggle when dealing with stress because of their lower awareness for their own feelings. They might not realize they’re burning themselves out until after it’s already too late. This is why it can be helpful to keep a notebook or journal handy for times when the negative feelings are piling on and they’re hard to identify. Writing out the details of an experience can often help work out what some of the feelings are, which lets the TiNe form a plan of action to stop them from progressing any further. They can also work through the same process with a close friend or partner - the important thing is that the feelings get taken out into the real world through writing them out or talking about them rather than being kept inside and analyzed to death.