Does Blood Type Determine Personality? What the Science Says

Theories about personality^{1https://opentext.wsu.edu/psych105/chapter/10-2-what-is-personality/#:~:text=Personality%20has%20been%20studied%20for%20over%202%2C000%20years%2C%20beginning%20with,formed%20through%20early%20childhood%20experiences.} have been around since the Middle Ages.

Whether our fascination comes from a desire to be understood or find our place in the world, something about our human desire to understand who we are keeps us intrigued.

In this article, we’ll look at the history behind the blood type personality theory, its weaknesses, and whether there could be a correlation between your blood type and your personality.

What is Blood Type Personality Theory?

The blood type personality theory suggests that blood types can determine personality and temperament due to correlations between a person’s blood group system^{2https://www.cancer.gov/publications/dictionaries/cancer-terms/def/abo-blood-group-system} and personality traits. 

For example, here are some of the personality traits that fall under each blood type according to the theory:

• Type A blood personality: friendly and agreeable
• Type B blood personality: spontaneous or neurotic 
• Type O blood personality: confident and extroverted 
• Type AB blood personality: some combination of personality traits from both A and B blood types, typically idealistic and conscientious

Some research suggests^{3https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4433257/} that if your blood type is genetic, then your personality could be inherited and determined by your blood type. However, scientists need to come to a clear consensus on the theory, and it is primarily considered a pseudo-scientific belief based on superstition, much like astrology. 

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What Are the Origins of the Blood Type Personality Theory?

Though knowledge of different blood types was not yet known until the 1900s, the origins of the blood type personality theory stem as far back as the Middle Ages when some philosophers believed^{4https://www.tandfonline.com/doi/abs/10.3109/08039489709090734} personality to be inherited biologically. 

Later in 1901, an Austrian scientist named Karl Landsteiner^{5https://www.nobelprize.org/prizes/medicine/1930/landsteiner/biographical/} discovered different blood types, which helped advance medicine significantly. (Unfortunately, this discovery also later led Nazis^{6https://www.jstor.org/stable/10.7829/j.ctt1282zr} to believe that some blood types were superior to others.)

In 1927, Japanese professor Takeji Furukawa^{7https://www.jstage.jst.go.jp/article/jjpjspp/3/1/3_KJ00001287020/_article/-char/en} published a paper^{8https://www.tandfonline.com/doi/abs/10.1080/00224545.1930.9714153} on his theory about the relationship between blood type and personality, which gained popularity despite a lack of credible scientific evidence.

Though Furkawa’s ideas fizzled out over time, a journalist with no medical background named Masahiko Nomi^{9https://en.wikipedia.org/wiki/Masahiko_Nomi} revived the theory in the 1970s, making it widely popular despite uncontrolled, anecdotal evidence criticized by psychologists.^{3https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4433257/} His book, Ketsueki-gata de Wakaru Aisho (Understanding Affinity by Blood Type) was a best seller. The theory remains popular today, partly due to his son Toshitaka Nomi’s promotion. 

The Impact of The Blood Type Personality Theory in Culture

The blood type personality theory has been popularized in Japanese^{10https://japantoday.com/category/features/lifestyle/the-importance-of-blood-type-in-japanese-culture} and Korean^{11https://gogohanguk.com/en/blog/the-significance-of-blood-type-in-korea/} cultures over the last century. It is not uncommon for people from these cultures to ask about each other’s blood types to determine personality, much like some Americans enjoy connecting over star signs in astrology. And like astrology, some take it so seriously that they even use it to match with potential partners or decide their career paths, while others turn to it simply for fun. 

It is so prevalent in Japanese culture^{10https://japantoday.com/category/features/lifestyle/the-importance-of-blood-type-in-japanese-culture} that blood types are often public knowledge, including for political figures and celebrities. Unfortunately, like many personality type profiling, it can often lead to negative stereotyping based on a widely accepted notion about how some types behave. 

Personality profiling continues to be used in job interviews, match-making sites, and everyday life to stereotype people’s behavior and makes major decisions about how to relate to one another. In fact, a Japanese term known as “bura-hara”^{12https://archive.nytimes.com/schott.blogs.nytimes.com/2009/03/05/bura-hara/} refers to the harassment people experience based on their blood type. It is known to cause bullying, deny people job opportunities, and end relationships. 

Is There Evidence for the Connection Between Blood Type and Personality?

Blood type theory is based on the idea that part of your personality involves genetic markers^{3https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4433257/}. Thus, since blood type might be considered a genetic marker, your blood type could determine your personality. 

However, in 2014, Kengo Nawata researched^{13https://www.jstage.jst.go.jp/article/jjpsy/85/2/85_85.13016/_pdf} a large sample size of 10,000 people, which concluded that blood type contributed to less than 0.3% of the total variance in personality. 

Some research suggests^{14https://www.researchgate.net/publication/228381093_Blood-typical_Personality_Stereotypes_and_Self-fulfilling_Prophecy_A_Natural_Experiment_with_Time-series_Data_of_1978-1988} that when someone discovers their blood type and a potentially correlating personality, they may believe in the theory simply due to a self-fulfilling prophecy^{15https://dictionary.apa.org/self-fulfilling-prophecy}. This is also common among people who believe in horoscopes and astrology^{16https://www.sciencedirect.com/science/article/abs/pii/S0191886916307826}.  

For example, suppose you discover that you have O-type blood and that the personality associated with O-type blood is someone confident and assertive. In that case, you might come to believe that you are a confident, assertive person or act confidently due to your belief. 

What is the Most Common Blood Type Personality?

Some blood types^{17https://www.statista.com/statistics/1112664/blood-type-distribution-us/} are more common than others, with O positive being the most common blood type in the U.S. (38%), followed by A positive (34%), B positive (9%), O negative (7%), A negative (6%), AB positive (3%), B negative (2%), and AB negative 1%. 

Based on this analysis, and if the blood type personality theory were true, the personality correlated with someone with type O blood would be the most common in the U.S. This means that a higher percentage of the population would be associated with personality traits including confidence, extroversion, and optimism. 

While the U.S. is dominated by type O blood, other parts of the world, like Europe and Japan, mostly have type A blood, and Pakistan and Bangladesh mostly have type B blood. Check out this helpful visual from the Visual Capitalist^{18https://www.visualcapitalist.com/visualizing-the-most-widespread-blood-types-in-every-country/}.

What Does Your Blood Type Say About Your Personality?

Research shows^{19https://www.researchgate.net/publication/29457792} no correlation between your blood type and your personality, despite the popularity of the blood type personality idea. That said, if you’re curious about the personality types that are believed to be associated with each blood type, check out these blood type profiles. 

O blood type personality

According to the blood type personality theory, people with type O blood are often seen as:

• Confident
• Aggressive
• Realistic
• Extroverted
• Optimistic

A blood type personality

According to the blood type personality theory, people with type A blood are often seen as:

• Careful
• Considerate
• Hard-working
• Friendly
• Agreeable

B blood type personality 

According to the blood type personality theory, people with type B blood are often seen as:

• Spontaneous
• Creative
• Neurotic
• Adaptable
• Playful

AB blood type personality 

According to the blood type personality theory, people with type B blood are often seen as:

• Idealistic
• Private
• Sensitive
• Studious
• Conscientious

How to Figure Out Your Personality Type

There are many tools and resources out there to choose from to help you figure out what your personality type might be, including personality quizzes and tests designed for self-discovery. 

Some popular personality taxonomies include:

• Myers-Briggs: Based on Carl Jung’s theory that you experience the world in four psychological functions, including sensation, intuition, feeling, and thinking.
• Enneagram: Suggests you have one of nine possible basic personality types based primarily on your intrinsic motivations.
• DISC: Used primarily in workplace settings to determine how you get results, influence others, cooperate, and maintain quality. 
• Motivation Code: Used to help people determine what motivates and engages them.
• CliftonStrengths: Used commonly in workplace settings to understand individual strengths and build better complementary teams.
• Working Genius: Suggests that people work within one of six different styles, including wonder, discernment, enablement, invention, galvanizing, or tenacity.

For fun, check out our article What Your Halloween Costume Says About Your Personality!

Blood Type Personality Theory Takeaways

In summary, take note of these considerations as you determine whether utilizing knowledge of your blood type helps you understand your personality.

• Blood type personality theory suggests that blood types can determine personality.
• Scientists cannot come to any clear consensus on the theory.
• The theory remains popular today, despite a lack of evidence, likely in part due to people using it as a self-fulfilling prophecy.
• Personality profiling can cause people to stereotype others negatively. 
• There are several personality type resources and tools to utilize outside of blood type personality theories. 

Have you ever wondered if you have the personality type to become president? Check out our article 7 Personality Traits You Need to Become President.