Blood type personality: is it real? What research says

Blood type personality is a popular belief that ABO blood type decides your personality: A is careful, B is carefree, O is generous, AB is hard to read. It is huge in Japan, Taiwan and other parts of East Asia and much less common in the US, but from 2,681 Taiwanese high-school students to surveys of more than 10,000 people in Japan and the US, research has never found a meaningful link between blood type and personality. It still feels accurate to many people because the descriptions are broad, we remember the hits, and many grew up hearing them. Blood type is fine as dinner-table small talk, as long as it does not become a label stuck on someone.

What is blood type personality? The popular story of A, B, O and AB

Blood type personality maps ABO blood type onto four personality stereotypes, and the table shows the version most familiar in East Asia. Searches for blood type personality, blood type traits and blood type and personality all mean the same thing.

The shares are from the Taiwan Blood Foundation (2023): O is most common, A and B are about equal, and AB is roughly 1 person in 16. The same page notes that shares differ by country: A is the most common type in Japan at 38.6%, O and A each make up roughly 35 to 40% of people in Europe and the US, and B only about 10%. These figures come back later, because they explain part of the feeling that “every O friend is so easygoing.”

The two middle columns are not research findings. They are the descriptions repeated most often in web articles, magazines and Japanese TV shows. A type’s strengths and weaknesses are often the same trait described two ways: A’s “careful” and “fussy,” O’s “dependable” and “bossy” differ only in whether the speaker likes you.

Where does blood type personality come from? A 1927 paper and a 1971 mass-market book

The blood type personality theory is under a hundred years old, and today’s popular version comes mostly from mass-market books in 1970s Japan. It is not some ancient Eastern wisdom.

The ABO blood groups themselves were described in 1901 by the Austrian physician Landsteiner: when different people’s blood is mixed, red cells sometimes clump together, because people have different blood types. That discovery made transfusion safe and earned him the 1930 Nobel Prize in Physiology or Medicine. From the start blood type was a medical matching question, unrelated to personality.

The person who linked blood type to personality was the Japanese scholar Takeji Furukawa, who published a paper in 1927 in the journal The Japanese Journal of Psychology arguing that blood groups differ in temperament. It drew a lot of attention, but Nawata (2014) summarizes that many later replication studies found it academically untenable, and research went quiet for a while.

What put it into everyday life was the writer Masahiko Nomi, whose 1971 book on whether two people are compatible by blood type was followed by a series of books arguing that blood type decides personality. The craze has returned again and again since: in 2004 as many as 70 Japanese TV programs ran blood-type specials, and in 2008 four “owner’s manual” books for the blood types, led by Owner’s Manual for B Types (title translated), all landed in that year’s top ten Japanese book sales (all from Nawata, 2014).

That 2004 wave also brought in an industry watchdog. The BPO (Japan’s Broadcasting Ethics and Program Improvement Organization, a third-party body set up jointly by NHK and the Japan Commercial Broadcasters Association) had its Youth Committee issue a request that December asking broadcasters not to encourage the view that blood type determines personality. Among the viewer comments the committee received were that blood-type programs were already fueling a mindset of discriminating by blood type at schools and in job hunting, and objections to programs using kindergarten children as subjects of a “blood type experiment.”

Is blood type personality accurate? Large studies find almost no difference

Based on current research, blood type personality is not accurate: the larger the sample and the more rigorous the method, the closer the personality differences explained by blood type get to zero.

Most relevant to Taiwan is Wu, Lindsted and Lee (2005). They had 2,681 Taiwanese high-school students complete the Chinese version of the Big Five inventory NEO-PI-R and report their blood type. Blood type had no significant relationship with any of the Big Five, with one exception: AB girls showed a small difference in conscientiousness, which the authors thought could simply be chance because there were so few AB girls. The authors also noted this was the first published study in Asia to test blood type with the Big Five model, the framework personality psychology uses most today. To learn more about it, see the full guide to the Big Five.

Nawata’s (2014) data set is even bigger. He analyzed three large random-sample social surveys, Japan in 2004 and 2005 and the US in 2004, over 10,000 people in all, and tested 68 items across the three surveys, of which 65 showed no significant difference across the four blood types. For the 3 items that did, Nawata calculated that testing 68 times would produce 3.4 “significant” results on average by chance alone.

The most interesting of the 3 is “worrying about children’s future.” It reached significance in both the Japan 2004 and US 2004 data (but not Japan 2005), but in Japan AB scored highest while in the US AB scored lowest, in opposite directions. If blood type really affected personality, it would be hard to explain why the same item flips in another country.

How small is the difference? Nawata calculated that blood type explained at most 0.3% of individual differences. As an analogy, take all the differences between people on one item as 1,000 parts: blood type gets at most 3. Psychology’s usual threshold for a “small effect” is 1%, and blood type does not reach that line. On the item with the biggest difference, the gap was only 0.25 points on a 1 to 5 scale.

These studies have limits, so here they are. Nawata used lifestyle-attitude items from social surveys, such as “worrying about life in old age,” which are not standardized personality scales, though the Taiwan study used a formal personality inventory and reached the same conclusion. On the other side, Tsuchimine and colleagues (2015) used genotyping to confirm blood type in 1,427 healthy Japanese participants and found a statistical difference in “persistence,” but the effect size was about 1% or less and the authors themselves called it preliminary and to be interpreted cautiously. Nawata’s review also mentions that studies of Canadian university students (Cramer & Imaike, 2002) and Australian blood donors (Rogers & Glendon, 2003) likewise found no meaningful difference.

More precisely: most studies could not measure a difference, and the few that did found differences that were very small, unstable, and nothing like “A is careful, O is generous.”

Why does blood type personality feel so accurate?

It feels accurate mostly because descriptions are broad, we remember the hits, and after years of hearing them we come to see ourselves through them.

The descriptions are broad. Psychologist Forer (1949) gave students a “personal” personality analysis, and everyone rated it accurate, when in fact everyone had received the same text. This is called the Barnum effect. A line like “easygoing on the surface, with firm views inside” fits under any blood type. The enneagram guide uses the same principle to explain why type descriptions make people nod.

We only remember the hits. In Taiwan, more than four in ten people are O. You naturally know plenty of O friends, some outgoing and some shy, but “see, the O is so easygoing” is easier to remember, and the shy one is quietly skipped. The same logic works anywhere one type is common, and whichever type is rare where you live gets fewer stories to confirm it.

After hearing it for years, do you live up to it? Nawata’s (2014) review summarizes two findings. In studies by Yamaoka (1999, 2006), people who believed in blood type theory rated their own personality differently by blood type, while those who did not believe showed almost no difference; and Sakamoto and Yamazaki (2004) found that during the 1980s peak of the craze, Japanese A types described themselves as more and more “A-like.” Even if that self-fulfilling effect exists, it is a self-image taught by society and not something in the blood. Nawata also adds that the 2000s data he analyzed did not show such differences, so the evidence here is itself mixed.

To test it yourself, try a blind-reading experiment at your next get-together:

1. Copy out the description for each of the four blood types, remove the headings, shuffle them and number them 1 to 4.
2. Have each friend pick the one that fits them best and write it down before anyone announces anything.
3. Then everyone says their real blood type, and you count how many picked their own.

If blood type really decided personality, hits should be well above one in four. With few people, luck plays a part, so treat it as a game, and after a few rounds you can see roughly where the hit rate settles.

How do you play with blood type personality without hurting anyone?

The best use of blood type is as an icebreaker. Using it to judge someone’s ability, love life or fit for a job crosses a line.

In East Asia, blood type turns up in these places: a new coworker asking “what’s your blood type?” at lunch, a group chat forwarding a meme like “never date a B type,” a dating profile listing it, and someone saying “let the A type write it up” in a group project. Most of the time it is just for fun, but a few lines are worth watching:

• Saying it about yourself is fine, and about others deserves a pause. “I’m A, so I’m a bit fussy” is self-teasing, while “you’re B, no wonder you’re so irresponsible” becomes an accusation that is hard to answer because blood type is inborn and cannot be changed.
• Do not let compatibility charts run your love life. Blood type compatibility gets plenty of searches, but since blood type and personality show no reliable link, the charts have even less basis. How two people communicate and make up after a fight is far more useful than a chart saying types clash.
• Schools and workplaces should not divide work by blood type. BPO’s 2004 request itself noted that viewers said the theory was already fueling discrimination by blood type at schools and in job hunts. Asking blood type in an interview or sorting tasks by it is unfair to whoever lands in an “unpopular” type.
• Do not use blood type to explain children. There are online articles about raising kids by blood type, but the BPO’s specific worry was children growing up believing blood type sets their personality. Who a child becomes has plenty of room left to change.

How is the “which blood type do you live like” quiz scored? It skips your blood type and looks at your choices

Our Which Blood Type Personality Are You? quiz does not use your real blood type to score your result. It uses 18 everyday scenarios to see which blood type stereotype your choices resemble most. Bluntly, it measures whether your daily choices look like what people say a type A does, not what runs in your veins.

The scenarios are everyday American ones: how you order at a coffee shop, what you take on when the group chat plans a cookout, what you do when the crowd at a street fair wants different food stalls. Each question has 4 options, and each maps to one vibe: the main vibe you pick gets 2 points, and a related vibe gets 1 more. That extra point is distributed by design so that each question gives every vibe one turn, so no type has a built-in advantage. The 18 questions total 54 points, converted to percentages across the four vibes that add up to exactly 100%.

Two useful reference numbers come from the scoring rules. First, even if you pick the same vibe on every question, that vibe’s share tops out at 67%, because every question gives 1 point to another vibe, so a “100% pure A” does not exist in this quiz. Second, we counted every possible answer combination for the 18 questions, treating each as equally likely, and found that for about 87% of them, the top vibe lands between 28% and 37%, and only about 5% go above 40%. So a main vibe above 40% means your choices are quite consistent, and around 30% means a mix of all four.

The last question asks your real blood type. It is optional, not scored, does not affect your result and does not appear on the share image or in your history. If you fill it in, the report adds an “on paper vs. in practice” comparison. If your blood type is B and your vibe looks most like A, that gap echoes the research above: blood type and how you live were never tied together.

Want to know yourself better? Move from blood type to tools with evidence behind them

If what you want is a personality description that measures something real, the Big Five is the model with the most research support, and blood type can stay at the dinner table.

Pick whichever of these suits you first:

1. Take the Blood Type Vibe quiz, then compare with your real type. See how far your main vibe is from your real blood type, and post a screenshot to the group chat, which beats arguing about whether B types are hard to live with.
2. Run the blind-reading experiment at dinner. Use the three steps above and let friends see the hit rate for blood type descriptions themselves.
3. For a serious look at yourself, switch to a tool with research. The Big Five measures five continuous traits and has the most research behind it. You can also read about how 16 personality types describes preferences with four letters, or start with one dimension in what I and E mean.
4. When someone reaches a conclusion from blood type, ask differently. Swap “you’re O, no wonder you’re so pushy” for “did you decide that because time was tight?” and the conversation gets more concrete.

If you have been teased or shut out at school or work over blood type, a zodiac sign or any label, and it is affecting your sleep, school or work, talk to a school counselor, HR or someone you trust. When your mood is too low to carry, you can call or text 988, free and open 24/7.