What is the Japanese blood type theory of personality?

In some Asian countries, what's in your blood determines who you are.

  • In Japan and South Korea, there is a common belief that blood types determine character much in the same way Western countries believe in the zodiac.
  • While there's little scientific evidence to back up the claim, the blood type theory of personality remains wildly popular.
  • However, how this theory came to be has its roots in a dark history.

If you were to ask a stranger at a bar what their blood type was, the best-case scenario in most of the world would be that you'd receive some very strange looks. But if you were in Japan or South Korea, you might actually get a response. In these cultures, blood type is believed to influence personality much in the same way that zodiac signs work in Western cultures. The reason why this came to be a cultural phenomenon in these places, though, has something of a dark history.

How the blood types break down

For the curious, here's how the system works. People with type A blood are warm, friendly, compassionate, and kind. They get along well with people and make good friends. However, they can be a little obsessive, fastidious, and shy. Sometimes their affection can be overbearing, and they tend to neglect their own happiness. Since the blood type personality theory parallels the zodiac sign system, there's also romance a component: Type A people should try to date other type A people or type AB people.

Type Bs are creative, outgoing, spontaneous, and extroverted. On the negative side, they can be self-centered, impatient, and overly independent. Their dating life looks like type As': they should date other type Bs or type Abs.

Type ABs are, naturally, a mix of type A and type B qualities. They somewhat contradictory—they can be shy at times and outgoing at others. They are considered to be very rational and adaptable, but they can be critical, indecisive, and aloof. Since they're so flexible, they can date pretty much anybody.

Type Os are confident, strong-willed, and competitive. On the negative side, they can be very selfish, arrogant, and aggressive. Again, their best bet is to date other type Os or type ABs.

While there are other blood types out there—like the so-called "golden" blood type, Rh-null—the personality theory really only accounts for the major types listed above.

It's certainly fun to compare and contrast the purported traits with yours and others' blood types, but like zodiac signs, there's little scientific evidence to back up the claims. However, the history of the blood type personality theory does have its roots in academia.

From eugenics to pop psychology

Tim Boyle/Getty Images

Blood types were first discovered in 1901 by the Austrian physician Karl Landsteiner. The discovery was monumental. If an unfortunate individual were to receive a blood transfusion from an incompatible donor, they could expect a host of undesirable symptoms: fever, burning sensations, chills, the formation of lethal blood clots in the veins, and an inexplicable sense of impending doom.

While it ultimately became one of mankind's greatest medical achievements, this research was also turned to dark ends. In the early 20th century racially charged thinking and eugenics were growing in popularity across the world. The Nazis would become obsessed with the idea of blood purity. The different blood types were believed to correspond to the different races, and although the ratio of blood types do vary by ethnicity, researchers at this time also ascribed different racial characteristics according to blood type. In particular, type B blood was seen as degenerate. As reported by Der Spiegel, one bacteriologist claimed that carriers of type B blood had more "individuals identified as inferior," and that the blood type often found in "psychopaths, hysterics and alcoholics" as well as—weirdly—"brunette individuals."

By the mid-1920s, this strand of research had made its way to Japan. One study by the social psychologist Takeji Furukawa titled "The Study of Temperament through Blood Type" put forth the first iteration of the blood type personality theory. His study was significantly flawed, as it used an excessively small sample size and unsound statistical methods to reach its conclusions. Furukawa, however, enthusiastically promoted the research, and it took hold in Japan. Some employers began including a box in their job applications to see if potential hires had compatible blood types for the work, and the increasingly nationalistic and expansionistic Japanese government even began to apply the concept in their military, going so far as to group soldiers by their blood types.

Furukawa himself argued that the blood type personality theory could be useful in the field of eugenics, which had become the subject of a great deal of interest in Japan during the first half of the 20th century. Some pundits believed that it was essential for the Japanese to remain junketsu or pure bred, while others argued that konketsu or mixed-bred Japanese could acquire desirable qualities believed to be found in other races. Furukawa would later engage in a study of Taiwanese blood types to try and clarify why they so passionately resisted being conquered by Japan in 1895. Since the majority of Taiwanese were type O, he concluded that it was due to the alleged type O tendency towards aggression and stubbornness.

How did this disturbing history translate to the comparatively banal (though sometimes still discriminatory) practice of using blood type that we see in modern Japan and South Korea? As the 20th century moved on, the idea of blood types having an influence on personality dropped from the public consciousness until the 1970s, when it was revitalized by a journalist named Masahiko Nomi. Nomi's work removed much of the racist and eugenic aspects of the theory's earlier incarnation. Once again, the subject proved to be wildly popular. Nomi published 65 bestselling books, and, after his death, his son Toshitaka Nomi continued the work until his own death in 2006. The modern incarnation of the blood type personality theory largely originates from these two writers, and, although it is significantly less prejudiced than it was in the early 20th century, people are still sometimes bullied or denied employment because of their blood types. There's even a term for harassment based on blood type: bura hara.

The scientific community

Although the theory has clearly captured the attention of many Japanese and South Koreans, its scientific evidence remains scant. A study by Kengo Nawata, for instance, studied the blood types and personalities of over 10,000 people and found that blood type explained just 0.3% of the variation in personalities, a number that could easily result from statistical error. Other researchers have found that blood type does have a relationship with personality in countries where belief in the blood type personality theory is strong. This study concluded that people changed their personalities to fit their blood type instead in a self-fulfilling prophecy.

The theory certainly holds more water than the idea that zodiac signs influence personality. It's difficult to see how the position of the stars could have an effect on an individual, but its conceivable that some genetic factors might contribute to both blood types and personality to some extent. Still, the bulk of the scientific research on the topic has failed to find any significant correlation between personality and blood type, with only a few controversial outliers. While the idea might be a pleasing diversion, it's probably for the best that human beings aren't so easily placed into boxes based on whether they're a Taurus or a type B. If one had to choose between a world where one's personality was determined by circumstance or molded throughout the course of one's life, most would probably prefer the latter.

Big Think Edge
  • The meaning of the word 'confidence' seems obvious. But it's not the same as self-esteem.
  • Confidence isn't just a feeling on your inside. It comes from taking action in the world.
  • Join Big Think Edge today and learn how to achieve more confidence when and where it really matters.

One victim can break our hearts. Remember the image of the young Syrian boy discovered dead on a beach in Turkey in 2015? Donations to relief agencies soared after that image went viral. However, we feel less compassion as the number of victims grows. Are we incapable of feeling compassion for large groups of people who suffer a tragedy, such as an earthquake or genocide? Of course not, but the truth is we aren't as compassionate as we'd like to believe, because of a paradox of large numbers. Why is this?

Compassion is a product of our sociality as primates. In his book, The Expanding Circle: Ethics, Evolution, and Moral Progress, Peter Singer states, "Human beings are social animals. We were social before we were human." Mr. Singer goes on to say, "We can be sure that we restrained our behavior toward our fellows before we were rational human beings. Social life requires some degree of restraint. A social grouping cannot stay together if its members make frequent and unrestrained attacks on one another."

Attacks on ingroups can come from forces of nature as well. In this light, compassion is a form of expressed empathy to demonstrate camaraderie.

Yet even after hundreds of centuries of evolution, when tragedy strikes beyond our community, our compassion wanes as the number of displaced, injured and dead mounts.

The drop-off in commiseration has been termed the collapse of compassion, (Slovic 2007).¹ The term has also been defined in The Oxford Handbook of Compassion Science: ". . . people tend to feel and act less compassionately for multiple suffering victims than for a single suffering victim."²

That the drop-off happens has been widely documented, but at what point this phenomenon happens remains unclear. One paper, written by Paul Slovic and Daniel Västfjäll, sets out a simple formula, ". . . where the emotion or affective feeling is greatest at N =1 but begins to fade at N = 2 and collapses at some higher value of N that becomes simply 'a statistic.'"³

The ambiguity of "some higher value" is curious. That value may relate to Dunbar's Number⁴, a theory developed by British anthropologist, Robin Dunbar. His research centers on communal groups of primates that evolved to support and care for larger and larger groups as their brains (our brains) expanded in capacity. Dunbar's is the number of people with whom we can maintain a stable relationship — approximately 150.

Some back story

Professor Robin Dunbar of the University of Oxford has published considerable research on anthropology and evolutionary psychology. His work is informed by anthropology, sociology and psychology. Dunbar's Number is a cognitive boundary, one we are likely incapable of breaching. The number is based around two notions; that brain size in primates correlates with the size of the social groups they live among and that these groups in human primates are relative to communal numbers set deep in our evolutionary past. In simpler terms, 150 is about the maximum number of people with whom we can identify with, interact with, care about, and work to protect. Dunbar's Number falls along a logorithmic continuum, beginning with the smallest, most emotionally connected group of five, then expanding outward in multiples of three: 5, 15, 50, 150. The numbers in these concentric circles are affected by multiple variables, including the closeness and size of immediate and extended families, along with the greater cognitive capacity of some individuals to maintain stable relationships with larger than normal group sizes. In other words, folks with more cerebral candlepower can engage with larger groups. Those with lesser cognitive powers, smaller groups.

The number that triggers "compassion collapse" might be different for individuals, but I think it may begin to unravel along the continuum of Dunbar's relatable 150. We can commiserate with 5 to 15 to 150 people because upon those numbers, we can overlay names and faces of people we know: our families, friends and coworkers, the members of our clan. In addition, from an evolutionary perspective, that number is important. We needed to care if bands of our clan were being harmed by raids, disaster, or disease, because our survival depended on the group staying intact. Our brains developed the capacity to care for the entirety of the group but not beyond it. Beyond our ingroup was an outgroup that may have competed with us for food and safety and it served us no practical purpose to feel sad that something awful had happened to them, only to learn the lessons so as to apply them for our own survival, e.g., don't swim with hippos.

Lapses

Imagine losing 10 family members in a house fire. Now instead, lose 10 neighbors, 10 from a nearby town, 10 from Belgium, 10 from Vietnam 10 years ago. One could almost feel the emotion ebbing as the sentence drew to a close.

There are two other important factors which contribute to the softening of our compassion: proximity and time. While enjoying lunch in Santa Fe, we can discuss the death toll in the French revolution with no emotional response but might be nauseated to discuss three children lost in a recent car crash around the corner. Conflict journalists attempt to bridge these geotemporal lapses but have long struggled to ignite compassion in their home audience for far-flung tragedies, Being a witness to carnage is an immense stressor, but the impact diminishes across the airwaves as the kilometers pile up.

A Dunbar Correlation

Where is the inflection point at which people become statistics? Can we find that number? In what way might that inflection point be influenced by the Dunbar 150?

"Yes, the Dunbar number seems relevant here," said Gad Saad, PhD., the evolutionary behavioral scientist from the John Molson School of Business at Concordia University, Montreal, in an email correspondence. Saad also recommended Singer's work.

I also went to the wellspring. I asked Professor Dunbar by email if he thought 150 was a reasonable inflection point for moving from compassion into statistics. He graciously responded, lightly edited for space.

"The short answer is that I have no idea, but what you suggest is perfect sense.

"One-hundred and fifty is the inflection point between the individuals we can empathize with because we have personal relationships with them and those with whom we don't have personalized relationships. There is, however, also another inflection point at 1,500 (the typical size of tribes in hunter-gatherer societies) which defines the limit set by the number of faces we can put names to. After 1,500, they are all completely anonymous.

"All this is set out in various articles and books. The two most obvious are: Dunbar (2016) Human Evolution. Oxford University Press (and) Dunbar (2014). The social brain: psychological underpinnings and implications for the structure of organizations. Current Directions in Psychological Research 24: 109-114."

I asked Dunbar if he knows of or suspects a neurophysiological aspect to the point where we simply lose the capacity to manage our compassion:

"These limits are underpinned by the size of key bits of the brain (mainly the frontal lobes, but not wholly). There are a number of studies showing this, both across primate species and within humans."

In his literature, Professor Dunbar presents two reasons why his number stands at 150, despite the ubiquity of social networking: the first is time—investing our time in a relationship is limited by the number of hours we have available to us in a given week. The second is our brain capacity measured in primates by our brain volume.

Friendship, kinship and limitations

"We devote around 40% of our available social time to our 5 most intimate friends and relations," Dunbar has written, "(the subset of individuals on whom we rely the most) and the remaining 60% in progressively decreasing amounts to the other 145." ⁵

These brain functions are costly, in terms of time, energy and emotion. Dunbar states, "There is extensive evidence, for example, to suggest that network size has significant effects on health and well-being, including morbidity and mortality, recovery from illness, cognitive function, and even willingness to adopt healthy lifestyles." This suggests that we devote so much energy to our own network that caring about a larger number may be too demanding.

"These differences in functionality may well reflect the role of mentalizing competencies. The optimal group size for a task may depend on the extent to which the group members have to be able to empathize with the beliefs and intentions of other members so as to coordinate closely…" This neocortical-to-community model carries over to compassion for others, whether in or out of our social network. Time constrains all human activity, including time to feel.

As Dunbar writes in The Anatomy of Friendship, "Friendship is the single most important factor influencing our health, well-being, and happiness. Creating and maintaining friendships is, however, extremely costly, in terms of both the time that has to be invested and the cognitive mechanisms that underpin them. Nonetheless, personal social networks exhibit many constancies, notably in their size and their hierarchical structuring." Our mental capacity may be the primary reason we feel less empathy and compassion for larger groups; we simply don't have the cerebral apparatus to manage their plights. "Part of friendship is the act of mentalizing, or mentally envisioning the landscape of another's mind. Cognitively, this process is extraordinarily taxing, and as such, intimate conversations seem to be capped at about four people before they break down and form smaller conversational groups. If the conversation involves speculating about an absent person's mental state (e.g., gossiping), then the cap is three—which is also a number that Shakespeare's plays respect."

We cannot mentalize what is going on in the minds of people in our groups much beyond our inner circle, so it stands to reason we cannot do it for large groups separated from us by geotemporal lapses.

Emotional regulation

In a paper,⁶ C. Daryl Cameron and Keith B. Payne state, "Some researchers have suggested that [compassion collapse] happens because emotions are not triggered by aggregates. We provide evidence for an alternative account. People expect the needs of large groups to be potentially overwhelming, and, as a result, they engage in emotion regulation to prevent themselves from experiencing overwhelming levels of emotion. Because groups are more likely than individuals to elicit emotion regulation, people feel less for groups than for individuals."⁶

This argument seems to imply that we have more control over diminishing compassion than not. To say, "people expect the needs of large groups to be potentially overwhelming" suggests we consciously consider what that caring could entail and back away from it, or that we become aware that we are reaching and an endpoint of compassion and begin to purposely shift the framing of the incident from one that is personal to one that is statistical. The authors offer an alternative hypothesis to the notion that emotions are not triggered by aggregates, by attempting to show that we regulate our emotional response as the number of victims becomes perceived to be overwhelming. However, in the real world, for example, large death tolls are not brought to us one victim at a time. We are told, about a devastating event, then react viscerally.

If we don't begin to express our emotions consciously, then the process must be subconscious, and that number could have evolved to where it is now innate.

Gray matter matters

One of Dunbar's most salient points is that brain capacity influences social networks. In his paper, The Social Brain, he writes: "Path analysis suggests that there is a specific causal relationship in which the volume of a key prefrontal cortex subregion (or subregions) determines an individual's mentalizing skills, and these skills in turn determine the size of his or her social network (Powell et all., 2012)"

It's not only the size of the brain but in fact, mentalizing recruits different regions for ingroup empathy. The Stanford Center for Compassion and Altruism Research and Education published a study of the brain regions activated when showing empathy for strangers in which the authors stated, "Interestingly, in brain imaging studies of mentalizing, participants recruit more dorsal portions of the medial prefrontal cortex (dMPFC; BA 8/9) when mentalizing about strangers, whereas they recruit more ventral regions of the medial prefrontal cortex (BA 10), similar to the MPFC activation reported in the current study, when mentalizing about close others with whom participants experience self-other overlap."⁷

It's possible the region of the brain that activates to help an ingroup member evolved for good reason, survival of the group. Other regions may have begun to expand as those smaller tribal groups expanded into larger societies.

Rabbit holes

There is an eclectic list of reasons why compassion may collapse, irrespective of sheer numbers:

(1) Manner: How the news is presented affects viewer framing. In her book, European Foreign Conflict Reporting: A Comparative Analysis of Public News, Emma Heywood explores how tragedies and war are offered to the viewers, which can elicit greater or lesser compassionate responses. "Techniques, which could raise compassion amongst the viewers, and which prevail on New at Ten, are disregarded, allowing the victims to remain unfamiliar and dissociated from the viewer. This approach does not encourage viewers to engage with the sufferers, rather releases them from any responsibility to participate emotionally. Instead compassion values are sidelined and potential opportunities to dwell on victim coverage are replaced by images of fighting and violence."⁸

(2) Ethnicity. How relatable are the victims? Although it can be argued that people in western countries would feel a lesser degree of compassion for victims of a bombing in Karachi, that doesn't mean people in countries near Pakistan wouldn't feel compassion for the Karachi victims at a level comparable to what westerners might feel about a bombing in Toronto. Distance has a role to play in this dynamic as much as in the sound evolutionary data that demonstrate a need for us to both recognize and empathize with people who look like our communal entity. It's not racism; it's tribalism. We are simply not evolved from massive heterogeneous cultures. As evolving humans, we're still working it all out. It's a survival mechanism that developed over millennia that we now struggle with as we fine tune our trust for others.

In the end

Think of compassion collapse on a grid, with compassion represented in the Y axis and the number of victims running along the X. As the number of victims increases beyond one, our level of compassion is expected to rise. Setting aside other variables that may raise compassion (proximity, familiarity etc.), the level continues to rise until, for some reason, it begins to fall precipitously.

Is it because we've become aware of being overwhelmed or because we have reached max-capacity neuron load? Dunbar's Number seems a reasonable place to look for a tipping point.

Professor Dunbar has referred to the limits of friendship as a "budgeting problem." We simply don't have the time to manage a bigger group of friends. Our compassion for the plight of strangers may drop of at a number equivalent to the number of people with who we can be friends, a number to which we unconsciously relate. Whether or not we solve this intellectual question, it remains a curious fact that the larger a tragedy is, the more likely human faces are to become faceless numbers.

¹ Psychic Numbing and Genocide, Slovic, 2007 https://www.apa.org/science/about/psa/2007/11/slovic.aspx

² The Oxford Handbook of Compassion Science, 2017 http://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780190464684.001.0001/oxfordhb-9780190464684-e-20

³ The More Who Die, the Less We Care: Psychic Numbing and Genocide

https://www.researchgate.net/publication/283318445_The_More_Who_Die_the_Less_We_Care_Psychic_Numbing_and_Genocide

⁴ Dunbar's Number https://en.wikipedia.org/wiki/Dunbar%27s_number

⁵ The Social Brain: Psychological Underpinnings and Implications for the Structure of Organizations http://www2.psych.ubc.ca/~schaller/358Readings/Dunbar2014.pdf

⁶Escaping affect: how motivated emotion regulation creates insensitivity to mass suffering. (Cameron, Payne 2011) https://www.ncbi.nlm.nih.gov/pubmed/21219076

⁷ Stanford paper: "Empathy for the social suffering of friends and strangers recruits distinct patterns of brain activation"

https://academic.oup.com/scan/article/8/4/446/1627027

European Foreign Conflict Reporting: A Comparative Analysis of Public News, Emma Heywood https://books.google.com/books?id=EAYqDwAAQBAJ&pg=PT115&lpg=PT115&dq=%E2%80%9CTechniques,+which+could+raise+compassion+amongst+the+viewers,+and+which+prevail+on+New+at+Ten&source=bl&ots=HgZpkKc-u5&sig=ACfU3U31FtWtYZby8QD9XQWR_8qMIHgnzA&hl=en&sa=X&ved=2ahUKEwj8ndu05dngAhXwnuAKHVFcDHcQ6AEwAHoECAkQAQ#v=onepage&q=%E2%80%9CTechniques%2C%20which%20could%20raise%20compassion%20amongst%20the%20viewers%2C%20and%20which%20prevail%20on%20New%20at%20Ten&f=false

Active ingredient in Roundup found in 95% of studied beers and wines

The controversial herbicide is everywhere, apparently.

(MsMaria/Shutterstock)
Surprising Science
  • U.S. PIRG tested 20 beers and wines, including organics, and found Roundup's active ingredient in almost all of them.
  • A jury on August 2018 awarded a non-Hodgkin's lymphoma victim $289 million in Roundup damages.
  • Bayer/Monsanto says Roundup is totally safe. Others disagree.
Keep reading Show less
Sponsored by the Institute for Humane Studies
  • There are 2 different approaches to governing free speech on college campuses.
  • One is a morality/order approach. The other is a bottom-up approach.
  • Emily Chamlee-Wright says there are many benefits to having no one central authority on what is appropriate speech.