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 TiSe’s functions are as follows:
1. Ti - internal Thinking
Ti makes decisions based on logical analysis done over time in their head. Because it is the TiSe's 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. Se - external Sensing.
Se is the main way TiSe’s take in information. It means they use their senses to understand the world around them. They live in the moment and prefer dealing with things that are real and solid over the purely theoretical.

3. Ni - internal iNtuition.
Ni is the TiSe’s third function, and it allows them to pull from every area in their brain to find solutions to problems, to look for patterns in the information they gather, or to skip ten steps ahead and predict what will happen in the future. Ni makes the Ti-led internal world very abstract and can involve lots of jumping around on intuitive leaps. This can make it hard for TiSe’s to fully explain the method they used to reach a certain conclusion.

4. Fe - external Feeling.
Fe is the TiSe’s last function. As a last function, it is inherently not as strong as the other functions. Fe is the TiSe’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 TiSe’s start out life being less aware of and equipped to deal with feelings than other types.


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 in order to be more objective. They often do this when problem-solving, meeting a new person or starting a new activity, or when arguing using reason.

Ti differs from Te (external Thinking) in that it doesn’t easily make near-instantaneous executive decisions. It does much better with time 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.

Ti is primarily concerned with learning. Not just gaining knowledge, but understanding complex things in a deep way. TiSe’s like to focus on real world problems and often have a strong appreciation for mastery and doing things with excellence and beauty. They don’t just want to learn, they want to be able to do something with it. Although they like having time to think about things, having Se means they can bypass Ti and take physical action when it’s clear and needed in the moment. This is why it’s important to have external functions as well as internal ones. If someone were purely Ti, they might never actually take action.

In preliminary neuroscience findings by Dario Nardi, Ph.D., strong Ti is correlated with being able to do multiple types of analysis at once. TiSe’s primarily use these two regions:

Spatial Navigation - Integrating visual-kinesthetic data. This aids in object identification, motor skills like aim, and mathematical calculations using a grid. This also helps us determine where we end and the rest of the world begins.

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, TiSe types can quickly engage these regions 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.

These types of analysis allow for skill in physically trying situations and problems with a high risk factor. TiSe’s often have a thrill-seeking side, and may enjoy sports, gambling, skydiving, bungee jumping, adventure travel or speeding down the highway in a sports car or on their motorcycle. TiSe’s are often perceived based on this side of them that loves adventure and needs thrilling new experiences, but what people often don’t see is the sharp mind behind it all. Because Se is external and therefore all about interacting with the real world, it’s obvious, but Ti is internal and hidden unless it’s intentionally brought out and shared.

Ti is combined with Ni in the TiSe to make an interesting combination of abstract objective analysis. Because much of the TiSe’s analysis is performed in their subconscious, it can be very tricky for them to eloquently describe their logic. This can also make it hard for others to see their intelligence. Ni is always seeking to understand things more deeply and wants to discover the core essence of things.

Se loves new experiences. It is always looking for something fresh to do or try. Ti needs fresh challenges and problems to solve, and love picking things apart to understand how they work. TiSe’s need constant challenges and can get bored if things are too easy. They may even take risks just to keep things interesting.

They are often most comfortable having expertise in something that involves hands-on or practical work. It’s best when their job and hobbies result in accomplishments are clear and measureable in the real world. Although they enjoy mastery, they don’t like to be masters at predictable or routine things. Their Ni particularly enjoys solving novel problems, so they can get bored easily when faced with repetitive procedural work. TiSe’s tend to enjoy things like graphic design, user experience, sports, the sciences, working on cars or motorcycles, sales, finance, or law. Psychology can also be appealing if they can see a way to make a real impact, as people are complex enough to provide an endless amount of variety and unpredictability.

Depending on what stage of development the TiSe is in, they may have different levels of comfort with more theoretical subjects, but generally speaking, Ni can handle the abstract as long as Se can see a clear use for it in the real world. Typically, if the TiSe chooses to invest in something like abstract algebra, it’s because they have a particular goal in mind for it. They generally don’t enjoy speculation for its own sake. Rather, they see knowledge as a tools of the mind, which enable them to be more capable at various tasks. Some TiSe’s find it useful to map out a general direction to make sure they actually get to where they want to go so that they don’t waste time learning things they can’t apply later on. While Se cares mostly about what is useful in the moment, Ni is able to provide balance by considering what might be needed in the future


External World

Se’s desire for adventure and need for freedom combined with Fe as the last function can lead to reckless behaviour for some TiSe’s, especially in their youth. They thrive on impulsiveness, and actually need it to feel alive. They might even enjoy breaking the rules at times. They love being able to do what they want, exactly when they think of doing it. Wanting to have fun and not caring what anyone thinks can be dangerous, but it can also have a positive side. TiSe’s are often willing to jump out on a limb and task risks where many others are not. With their Ti performing an analysis of the situation and their Ni predicting how things will play out in the future, they can take leaps with a degree of certainty and thrill that others simply don’t have. However, they may make others nervous if they forget to explain the detailed thinking that’s gone into their decisions.

When it comes to relationships, Se types tend to prefer doing things rather than just sitting and talking for hours. It’s important that the TiSe has and makes use of their Fe in relationships to ensure that they don’t get overly impatient and analytical with the people they love. An example of this: TiSe’s tend to be driven to solve a problem as soon as they hear about it, so if someone is talking about a problem they have and is expecting the TiSe to just listen instead of trying to fix things, they may get frustrated and simply stop listening if they feel like their solution isn’t wanted. However, actually listening even when a solution isn’t needed can be beneficial to the relationship as it makes the other person feel good. It can be helpful for the TiSe to ask whether someone wants a solution in these cases so they don’t have to resort to guessing.

Se prefers to learn as much as it can from personal experience and hands-on training. If it’s something they enjoy, Se types are often skilled at building and crafting things in the real world. TiSe’s love achieving mastery. They want to feel like they can produce something excellent time after time. When they experience something that’s been done with beauty and excellence, whether it’s art, a film, a website, or a table, their Ni gives them hints at why it’s beautiful and what makes it well-crafted. They’re able to use this in turn to make things with a high level of quality and craftsmanship.

While they may feel like they understand something fully in their head, TiSe’s may not be as adept at explaining things to others without practice. If a TiSe is interesting in passing along what they’ve learned, they may find it easier to show their students how to do it and walk them through the process in a hands-on way rather than focusing on the theory behind it.

TiSe’s usually love experiencing beauty or doing something fun that engages their senses. They might go on mountain hikes, do martial arts, or take a road trip, but they need this “sensory input” to stay fueled up. Without it, their energy levels, excitement, and creativity start to suffer.

Se is all about the experience of the moment. It is less concerned with the past or the future than it is excited about the now. This means they are always able to respond to the moment because they are fully present in it, while their Ti and Ni store away anything they learned for analyzing later. Ni doesn’t necessarily store the exact facts of a situation, but more the general feeling and vibe of it and more vague details, this can make it tough for TiSe’s to recall exact details about the past. However, the TiSe doesn’t usually find it necessary to remember every single detail in order to comprehend something. It’s more about getting an instinct for it, and seeing the underlying patterns behind how something works as they’re experiencing it. This can be highly useful in physical activities like sports. TiSe’s are also able to use their Ni to see themes and relationships between images, which can aid them in visual and artistic pursuits.

Fe, the TiSe’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. However, because Fe is last, having to do too much caring for others or feeling like they’re getting roped into more than they offered to do can make the TiSe frustrated and can leave them feeling taken advantage of and exhausted. TiSe’s need time away from others so that they can shut off their caring side and regain their energy.

TiSe’s like for people to get to the point and say what they really mean. They might get irritated when they feel like they are expected to pay attention and do all the right things in social situations. Often one must dance around stating the facts or go to great lengths to dress and act the part in order to gain favour in the sight of others, and TiSe’s can just get sick of it all after a while. Their low Fe also means they sometimes offend people and don’t even realize it until later, if at all. This can make it feel like they have to walk on eggshells with everything they say, and often they’d rather just avoid the entire situation than have to cater to everyone’s feelings.

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 TiSe’s do care deeply about social issues and the welfare of their communities, 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.

Emotionally speaking, often the best thing is for the TiSe to get comfortable with letting their Fe express feelings as they happen in a healthy way. This might look like going for a walk or drive and listening to loud music when they get angry to blow off some steam. In a positive sense, it can look like showing affection to their partner or children as it comes up in the moment.