Introverted Sensing /Sensation (Si), which serves as the dominant function for the ISTJ and ISFJ personality types, is among the least understood of the eight Myers-Briggs functions. In this post, I will attempt to clarify the nature and role of this rather enigmatic function, including its different manifestations in SJ types and NP types. We will also compare and contrast it with Extraverted Intuition (Ne) and Introverted Intuition (Ni).
Before zeroing in on Introverted Sensing, or what Jung dubbed Introverted Sensation, we need to first consider the context in which it occurs. According to type theory, which is founded on Jung’s theory of opposites, for every type in which Si is part of the functional stack, we also find its functional opposite, Extraverted Intuition (Ne). So in exploring the nature of Introverted Sensing, it can be helpful to juxtapose it with Ne.
Introverted Sensing / Sensation (Si) & Extraverted Intuition (Ne)
While Ne can be used synthetically to forge new connections, it also has a strong divergent element. Ne prompts us to explore more options and possibilities ad infinitum. Without the reality checks of other functions, an unbridled Ne can easily result in a sort of aimless wandering through life. Thus, one role of Introverted Sensing is to serve as a counterbalance and reality check to Ne. It does this by way of remembered facts and life experiences. We have all heard the phrase, “You learn through experience.” Si provides us access to our life history, as well as other sorts of acquired information, which hopefully prevents us from making the same mistakes twice.
It is also critical to recognize that Si will manifest somewhat differently depending on its relative position in the functional stack. For Si dominant types or auxiliary types, whom David Keirsey collectively coined the “Guardians” (SJ types), Si will play a different role than it will in the more liberal and freewheeling NP types. In SJ types, Si often translates into an adherence to existing facts, traditions, worldviews, or methods. These types are typically not well-equipped for, nor are they highly interested in, creating their own ideas or theories, which would require a stronger Ne. They are more concerned with ensuring their beliefs and behaviors are consistent with an existing standard than they are in formulating their own set of standards. In many ways, they are dependent on what has already been tried and established, systems of thought that grant them a sense of consistency and security.
When Introverted Sensing is lower in the stack, as in the case of NP types, it fails to provide the same degree of immediate and enduring certainty in their beliefs that we see in SJ types. This is due, at least in part, to the fact that NPs prefer to actively assemble their own theories about the world, relying less on tradition and conventions. Therefore, for NP types, the Si information utilized to aid and hone their Ne is often more personal in nature. NP types place a vast amount of trust in their personal experiences, making their perspectives among the most idiosyncratic and individualistic of all types.
Introverted Sensing can aid the personal growth and development of NP types by recalling to mind lessons learned from past experience. By remembering what they have already ruled out from past experiences or study, NPs feel they are, even if rather slowly, moving closer to certainty. Si can also help NPs develop effective habits. As NPs observe themselves over time, they can identify which behaviors allow them to function most optimally and feel the most satisfied. Then, when they start to get off track, their Si can step in and remind them of those behaviors that can help them return to a more balanced and healthy state. Since Si is inferior for ENP types, they may have the most difficulty developing and adhering to healthy habits.
Finally, one of the most commonly overlooked functions of Introverted Sensing is its role in perceiving internal bodily sensations—the body as felt and experienced from within. More than any other psychological function, Si provides access to our most basic sense of “being,” apart from thought or outward stimuli. Historically, Eastern philosophical and religious traditions have done a much better job exploring this aspect of human experience than those of the West. This dimension of Si is engaged during activities that require close attention to one’s internal bodily state, such as yoga, Tai-Chi, or meditation.
Introverted Sensing (Si) vs. Introverted Intuition (Ni)
Since Introverted Sensing is a Perceiving function, it can be understood, much like Introverted Intuition (Ni), as acting rather passively and outside of conscious control. Like INJs, SJs often experience a strong sense of conviction, a gut feeling about whether some is true or false, right or wrong. This, without having really done much as far as conscious reasoning to arrive at such conclusions. So while Si types may seem stubborn or closed-minded, they may feel that they have little as far as free choice in what they believe. This is why Jung considered Si an irrational function. Not because its conclusions are necessarily irrational, but because of the unconscious way it receives information and draws conclusions.
An excellent example of the irrational element of Introverted Sensing can be found in the book, The Woman Who Can’t Forget. There, the author explains her uncanny ability to accurately recall the details of each and every day of her life, including related historical dates and events. While her powers of memory are undoubtedly unprecedented, what is most telling with regard to her Si is that fact that she cannot control it. She reports feeling great frustration because her mind is constantly replaying memories in a random fashion, despite her best efforts to eliminate them and focus on the present. Even if extraordinary, her experience speaks to the passive, involuntary way in which Si in records and recollects information. This helps to explain why Si dominant types seem to effortlessly recall all sorts of random details and facts. Their recall is simply too quick to be attributed to conscious effort. Such displays of effortless and accurate memory why many non-Si types may see ISJs as unusually intelligent.
Finally, while Ni and Si are both irrational functions, Si is less synthetic and creative than Ni. Si more or less preserves and relays information in its original form. Ni acts more synthetically, weaving together disparate information to construct novel theories, visions, and insights.
To learn more about Si, be sure to explore our latest book, My True Type: Clarifying Your Personality Type, Preferences & Functions, which takes an in-depth look at each of the 8 functions and preferences: