The term "ambivert" was popularized by Dan Pink in 2013, in an article on leaders and sales. The word operates in the same colloquial universe of definitions in which introverts are shy and retiring and extroverts (usually spelled with an o) are loud and outgoing.
Here's an excerpt from Pink's article in the Washington Post:
So what kind of personality makes the best salesperson — and therefore, presumably, the most effective leader?
Most of us would say extroverts. These wonderfully gregarious folks, we like to think, have the right stuff for the role. They’re at ease in social settings. They know how to strike up conversations. They don’t shrink from making requests. ...
The conventional view that extroverts make the finest salespeople is so accepted that we’ve overlooked one teensy flaw: There’s almost no evidence it’s actually true. ...
Does this mean instead that introverts, the soft-spoken souls more at home in a study carrel than on a sales call, are more effective? Not at all.
The problem with these paragraphs (and with the entire article), is that extraverts are not, necessarily, "wonderfully gregarious folks..." and introverts are not (again, necessarily) "soft-spoken souls more at home in a study carrel". The problem with the article is that Pink is using the common misunderstandings of introversion and extraversion.
It's not entirely Pink's fault. He cites a study by Adam Grant (outspoken opponent of the MBTI):
...Grant collected data from sales representatives at a software company. He began by giving reps an often-used personality assessment that measures introversion and extroversion on a 1-to-7 scale, with 1 being most introverted and 7 being most extroverted.
Pink doesn't provide the name of the "often-used personality assessment" used in Grant's study, but, from this description, it sounds like the Big Five. In the Big Five model, one of the "Five Factors" is Extraversion: outgoing/energetic vs. solitary/reserved. (Introversion is not, in fact, an aspect of this scale. People are simply more, or less, "extraverted".)
Pink goes on to say:
Ambiverts, a term coined by social scientists in the 1920s, are people who are neither extremely introverted nor extremely extroverted. Think back to that 1-to-7 scale that Grant used. Ambiverts aren’t 1s or 2s, but they’re not 6s or 7s either. They’re 3s, 4s and 5s. They’re not quiet, but they’re not loud. They know how to assert themselves, but they’re not pushy.
Neither Pink nor Grant is using Jung's definitions of introversion and extraversion. Jung's definition of the words refers to energy flow. Is energy flowing inward or outward? Are you energized by internal thoughts or external stimulation?
Using Jung's definitions (which are also the definitions used by the MBTI, the Keirsey Temperament sorter, and other temperament theories based upon Jung's work) there is no place for ambiversion. Energy flow is one way or the other; it cannot be both. Energy flow may change – Jung's theory states that we all have the ability to use both introverted and extraverted Sensing, Intuition, Thinking, and Feeling functions – but not with equal comfort and not at the same time.
More recently, scientific data has supported Jung's theory by showing neurological differences between the brains of introverts and extraverts. Just as the ability to write well with the right hand does not turn a left-hand-dominant person into a right-hand-dominant person, the ability to "act like" an extravert (to "do both" when responding to a list of traits) does not turn introversion into extraversion, or vice versa.
Colloquially, an "ambivert" may be a person who does not appear, upon observation, to be extremely introverted or extremely extroverted. But observational behaviour (and "extremes" of such behaviour) do not underly the Jungian definitions of introversion and extraversion. In Psychological Type, there are no "extremes", only dichotomies.
In the models of psychological type that inherit from C. G. Jung, there is no place for "ambiversion".
In 2013, in response to a question in Linkedin, Peter Mann, MD at InterPersonality Pty. Ltd. wrote:
Oh Wow - again.
And right under the "Myers-Briggs Type Indicator® Assessment (MBTI®)" banner.
"Strictly speaking, there are no introverts and extraverts pure and simple, but only introverted and extraverted function-types."
C. G. Jung
By implication, there are no ambiverts.
To answer the question; an ambivert can remain ignorant of the theory underlying the MBTI and how a TYPE indicator actually works for as long as the intrigue of Ambivert label remains exciting ……
Added July 1, 2015:
...the eminent Carol Shumate has just posted an article in the online journal 'Personality Type in Depth' arguing against the notion of 'ambiverts' (a balance of the two attitudes) and cites this:
Jung is often cited as saying that “there is no such thing as a pure extravert or a pure introvert,” a misquote that is used to suggest that ambiversion is the natural, healthy state (see for example, Ankeny, 2015, p. 38). But the actual quotation, read in full, leads to a different understanding: “Strictly speaking, there are no introverts and extraverts pure and simple, but only introverted and extraverted function-types, such as thinking types, sensation types, etc.” (1921/1971, para. 913). In other words, the terms extraversion and introversion, are attitudes indicating the direction or orientation of the mental functions, not independent of the mental functions but inseparable from them. According to Jung, who introduced these terms into the psychological lexicon (Falzeder, 2013, pp. 10-12), we are always one-sided because we can only have one primary function: “Absolute sovereignty always belongs, empirically, to one function alone, and can belong only to one function, because the equally independent intervention of another function would necessarily … contradict the first” (para. 667).'
Added: February 2016
/via a 2016 posting (again in Linkedin), Jane Kise, Ed.D. wrote:
Ambivert is a correct term if you're using a five-factor tool such as the NEO-Pi. But in Jungian type ALL of us use both worlds. We have a preferred world, designated by the first letter in our four-letter code. The last letter tells us what we do in the external world (a J designates that in the external world we come to closure either through thinking or feeling and a P that we take in information through Sensing or Intuition). We use the other process in the internal world. The five-factor models, on the other hand, describe introversion as lack of extraversion. Ambiversion indicates a measurement whereas there is no measurement in Jungian type. Different models using same names that correlate and overlap but need different interpretations...