What does I and E stand for? Introvert, extrovert, ambivert

I and E stand for Introversion and Extraversion: they are the first letter of an MBTI type—I means leaning introverted, needing time alone to recharge, and E means leaning extroverted, getting more energized the longer you talk with people. Both labels are handy and funny, but in research introversion and extraversion are one continuous line, and most people stand somewhere near the middle. The rest of the article covers where the labels came from, the ambivert in the middle, and things an I and an E can say to each other over dinner, on a trip and across a weekend. If what you are really trying to separate is introversion from social anxiety, start with social anxiety vs introversion.

Introvert vs extrovert: what I and E mean

“I” and “E” are the first pair of letters in the MBTI: I stands for Introversion and E for Extraversion, and the internet turned them into handy labels for introducing yourself.

The MBTI builds 16 types from four pairs of preferences, and the E/I pair is about direction of energy: do you get more of your spark from people and events outside, or from your own inner world? What the other three pairs describe is covered in what are the 16 personality types. Academic writing sometimes says “extraversion” and “introversion” with different spellings, such as extroversion; they mean the same thing.

Everyday use is much looser than the original definition. Someone puts “INFP, big introvert” in a dating profile; someone answers a karaoke invite with “introvert battery’s at zero tonight”; someone calls a coworker “such an extrovert” for chatting with everyone the moment they walk into the office. In the Chinese-speaking internet the shorthand became “i ren” and “e ren,” literally “I person” and “E person,” and “big I” or “big E” means the very obvious end of either.

There is a gap between the online version and the psychology version:

Where the introvert and extrovert labels came from: South Korea’s MBTI boom and a Chinese buzzword

The “I person, E person” phrasing grew out of the MBTI boom online with no single inventor: the craze took off first among young people in South Korea, and in 2023 the “i ren / e ren” version went viral on the Chinese internet.

South Korea was one of the starting points. Jiang (2024), at Hanyang University’s graduate school of international studies, collected 231 Korean news reports and found that the MBTI became popular among younger Koreans from 2020, during the COVID-19 pandemic, and later a national topic. The author ties it to a post-pandemic wish to explore oneself and find like-minded circles online, with celebrity and fan-community talk giving it a push.

The craze soon spilled from chat into the workplace. In January 2022 the Korean newspaper The Kyunghyang Shinmun checked three part-time job sites and found eight employers that wrote the MBTI into their hiring criteria, all restaurants and cafes, most looking for E types; some companies also asked applicants to state their type in their cover letters. A researcher quoted in the article criticized this kind of test for forcing people into A or B with no room for a middle answer. A label made for chatting being used to screen people is the part of the I and E vocabulary that most needs care.

In the Chinese internet, “i ren / e ren” took off in 2023. ETtoday reported that the Chinese journal Language and Character Weekly named it first among its ten top web buzzwords of 2023; the report describes the MBTI as having replaced star signs as young people’s favorite social label for talking about personality and introducing themselves.

How the phrase spread elsewhere has not been studied or reported, so what follows is our guess: the Korean MBTI craze and the Chinese buzzword arrived around the same time, and many people were exposed to both, so it likely came in through several channels at once and is hard to pin on one.

Introversion is a line, and most people sit in the middle

In research, how extraverted someone is forms a continuous spectrum with most scores clustered mid-range; the boundary between I and E is a line the test draws in order to produce a letter, not two natural piles of people.

McCrae and Costa (1989) compared the MBTI with a Big Five inventory using data from 468 adults and found no evidence that the MBTI measures truly two-sided types; it measures four continuous dimensions, and E/I is clearly related to Big Five extraversion. For how the Big Five describes extraversion with scores, see what is the Big Five personality model.

More direct evidence comes from score distributions. Early on, some argued that MBTI scores were bimodal (one cluster leaning I, another leaning E, few in the middle), which was used to support the idea that people come in two kinds. Bess and Harvey (2002) rescored about 12,000 people who had attended leadership courses and found the bimodality was an artifact of the scoring settings; with the settings corrected, scores on all four dimensions clustered strongly in the middle.

Two practical conclusions follow:

• A figure like “about half of people are I” comes from forcing everyone onto one side, and it does not mean the world holds two kinds of people in equal numbers.
• Someone whose score hugs the midline can test I today and E next month without anything strange going on. Every test has error, and switching sides after a few points means you stand in the middle, not that the test is “wrong” or that you “have no personality.”

So when reading a result, how strongly you lean carries more information than the letter. Our 16-Type Personality Test has 9 questions for the energy pair (5 either-or scenarios and 4 five-point scale items). Each one adds or subtracts toward E or I, producing a raw score from −18 to +18, which is converted to a 0 to 100 clarity score:

The report also lists a “closest neighbor type”: the type you get by flipping the pair with the lowest clarity. If the least distinct pair happens to be energy, the neighbor is the type that differs by just one I/E letter, which means that on some days you look a lot like it.

What is an ambivert? One sales study and its limits

An ambivert is someone whose extraversion falls mid-spectrum, who can be lively or quiet depending on the setting, and going by the score distribution above, ambiverts are actually the most common group.

The most cited study is Grant (2013). He analyzed 340 call-center salespeople making outbound calls and found an inverted U between extraversion and sales revenue: people with mid-range scores outsold both the very extraverted and the very introverted. His explanation was that ambiverts speak and listen more flexibly, being warm enough to sell while also willing to hear what a customer cares about, and less likely to seem too eager or too sure of themselves.

The study has limits: the sample is one job, phone sales, and it is a single study. It is enough to shake the stereotype that sales teams must hire very extraverted people, and not enough to conclude that ambiverts do better in every line of work.

Another angle comes from Fleeson (2001). He asked participants to report their behavior several times a day over two to three weeks and found that ordinary people show nearly every level of extraversion in daily life: the same person is sometimes lively and sometimes quiet, with large swings, while their average stays quite stable. So most people move back and forth between the two modes, and the difference is where their average lands.

Can an introvert switch on extrovert mode? Free traits and recharge time

Yes, and many people do it every day; the research finding is that it has both benefits and costs, and whether it is worth it depends on what you are doing it for and whether you get time to recharge afterward.

Personality psychologist Little (2008) proposed the concept of “free traits”: people temporarily act out of character for things they care about. A naturally introverted teacher can lecture with real warmth for the sake of the students. He argues this helps you get important things done and makes life better, but holding it up for long stretches also wears you out, so you need “restorative niches,” such as retreating to an office after class or wearing headphones and saying nothing on the ride home.

Experimental results are mixed in the same way. In Jacques-Hamilton, Sun and Smillie (2019), one group deliberately acted extraverted for a week and their positive emotion rose overall; but the more introverted the participant, the smaller the rise in positive emotion, and negative emotion, fatigue and the sense of not feeling like themselves went up instead. More detail on the “social battery” and these studies is in social anxiety vs introversion.

In day-to-day office life, that can look like this:

• Switch on E mode only for the occasions you care about: a client presentation you fought for or the first dinner with a new team is worth it; being the life of every party costs a lot.
• Plan the recharge first: leave the day after the holiday party empty, and after a business-trip presentation keep half an hour to yourself.
• Find your restorative niche: half an hour over lunch with notifications off, twenty minutes on the commute home, the office stairwell all count.

How do introverts and extroverts get along? Scripts for dinners, trips, weekends and group chats

How well an introvert and an extrovert get on has little to do with whether their letters match; what usually trips people up is one person’s way of recharging being read as “they don’t care about me,” and that can mostly be fixed by saying it in advance.

Dyrenforth and colleagues (2010) used three nationally representative samples of married couples from Australia, the UK and Germany, more than 11,000 couples and more than 23,000 people combined, and found that once each person’s own personality was accounted for, personality similarity explained less than 0.5% of relationship satisfaction and of life satisfaction. What mattered more was each person’s own traits and whether the partner was agreeable, conscientious and emotionally stable. The study looked at similarity across the Big Five as a whole rather than extraversion alone, yet it does show that “you need similar personalities to get along” does not hold up well, and it leaves no research backing for declaring an I and an E a bad match on the letters alone.

Five situations come up a lot. One caveat: extroverts get tired and introverts want the party too, so these are preferences, not rules.

Lines you can borrow for each one:

• Dinner (I to E): “You go have fun. I’ll leave after the main course, so don’t count me for the next stop. I’ll text you when I’m home.”
• Dinner (E to I): “If you’re fading, give me a look and we’ll slip out. Next time I’ll do a quiet dinner with you.”
• Trip: “How about we split up from three to five every day? You hit the market, I nap at the hotel, and we meet for dinner.” If you share a room, you can agree on no talking for the hour before bed.
• Weekend: “I’ll go to your friend’s barbecue on Saturday, and on Sunday I’d like to do nothing at home all day. Is that okay?”
• Group chat: “I’ll reply a bit later. It’s not that I’m ignoring you all. Call me if it’s urgent.”
• Meetings: whoever is chairing can say, “Everyone take five minutes on your own and write it down, then we’ll go around.” Those who think out loud need not hold back, and those who think before speaking get time to do it.

If you both want to know what drains and recharges each of you most, take the Social Battery Test together. It splits the battery into four parts: Charged by people, Need for alone time, Craving deep talk and Soaking up moods. The type called the Solar-Powered Battery is a lot like the ambivert who shifts with the setting.

Do not let the letters become a box: three small exercises, and when to get help

The best use of “I” and “E” is as one sentence about your rhythm, and not as a verdict on yourself or anyone else; three exercises make the label more useful.

First, swap “I am” for “today I am.” “I’m an I, so I’m not going” shuts you out of the room; “I’m feeling more I today and want to head home early” only describes a state, and you can still go next time.

Second, swap a “recharge list” with your partner, roommate or a close friend: each writes down the three things that restore you most, such as watching a show alone, talking to someone on the phone, or grabbing a drink out. An extrovert’s recharge often needs company and an introvert’s needs to be left alone; once it is written down, nobody has to guess.

Third, next time you take a test, look at the clarity as well. The letter tells you which side you lean toward, and clarity tells you how far; once you know you are near the midline, there is no need to agonize over “am I really an I or an E?”

If what troubles you is dread beforehand rather than tiredness afterward, meaning worry about being judged or embarrassed, strong enough that you have started avoiding necessary things like presenting, interviews or seeing a doctor, and it has lasted several months, then I and E no longer explain it. Read social anxiety vs introversion and consider talking to a psychiatrist, clinical psychologist or licensed counselor.