What’s your type? To find out how your personality affects your future, forget horoscopes. The answer could be in your blood type

What’s your type? To find out how your personality affects your future, forget horoscopes. The answer could be in your blood type

Cody Crane


Many people in the U.S. believe that your astrological sign can reveal your personality traits and that reading your horoscope can predict your destiny. But many Japanese believe that the clues to people’s character and future lie not in the stars but in their blood type.

The idea that a person’s blood type influences behavior has been a part of Japanese popular culture for decades–ever since a book on the subject became a best-seller in the 1970s. Since then, some employers have used it to evaluate job applicants. Dating services consult blood types to pair couples. You can even purchase soft drinks and gum custom-made for your type. So, is blood type just a fortune-telling fad in Japan, or does it really reveal something about you?



All blood is made of the same components–red blood cells (oxygen-transporting cells), white blood cells (infection-fighting cells), platelets (factors that help blood clot), and plasma (the fluid that carries blood cells)–but not all blood is alike. Everyone has one of four possible blood types: A, B, AB, or O. Humans’ different blood types depend on the presence of molecules, called antigens, attached to the surface of red blood cells.

It is these antigens that are such a hot topic in Japan. “The belief that blood type is a clue to your personality is extremely widespread in Japan,” says Jennifer Robertson, an anthropologist who teaches Japanese history and culture at the University of Michigan. When people there first meet, “What’s your blood type?” might very well pop up in the conversation. “Blood type is one way people share information about each other. It also generates a sense of familiarity with people whom you might otherwise not get to know on a first-person basis,” says Robertson. That includes Japanese celebrities, politicians, and athletes, whose blood types are discussed in magazines, on TV, and even listed as a stat on baseball cards.


In Japan, the biological differences between blood types, of ketsuekigata, are thought to influence not only your personality, but also how you interact with others and even your ideal career.

People with Type O blood are considered to be outgoing and self-confident (see Blood Stats, pp. 8-9). These warrior-like qualities are believed to make them the best bankers, politicians–and even baseball players. Although the most common blood type in Japan is Type A, many famous Japanese baseball players are indeed Type O.

Does that confirm that blood type determines a person’s abilities on the ball field? Not necessarily, says Robertson. People who are expected to bit more home runs because of their blood type may be singled out to receive help to improve their game, or they might get moved to the start of the lineup where they have more opportunities at bat. Encouraging someone to become a good hitter, pitcher, or outfielder could help the person achieve just that, regardless of blood type, Robertson explains.


Whether you are classified on the basis of blood type as a “warrior” or “hunter” has nothing to do with fate. The blood type you’re born with depends on the genes, of units of hereditary material, you inherit.

There are three different alleles (forms of a gene) that control for blood type, one for A, B, and O. These alleles are responsible for producing the A and B antigens that tag red blood cells. The O allele doesn’t produce A or B antigens. The combination of alleles you receive–one from each parent–determines your blood type (see Nuts & Bolts, above).

A and B alleles are dominant traits. When either of these versions of the gene are inherited, A or B antigens are always present. Because A and B alleles are codominant, they can be expressed together, resulting in a person with copies of both alleles having blood cells marked with both A and B antigens.

When an A or B allele is paired with an O allele, the dominant traits will determine a person’s blood type. That’s because, “Type O is a recessive trait,” says Dr. Paul Holland, the scientific director of the Delta Blood Bank in Stockton, California. The only way for a person’s blood to be Type O is to inherit two O alleles.


While it’s estimated that 90 percent of people in Japan know whether they are Type A, B, AB, or O, many Americans are clueless about their blood type. In the U.S., people often don’t learn their blood type from a doctor unless they donate blood or need a blood transfusion, says Holland.

Why would a person find out his or her blood type during one of these procedures? Blood type reveals an important fact about each of us: whom you can give or receive blood from during medical treatments. If two people’s blood types are not a match, there could be serious consequences for the blood recipient.

“The body’s immune system is primed to destroy anything foreign,” says Holland. That includes the antigens of other blood types. If given blood with antigens that don’t match your own, proteins called antibodies would trigger the immune system to attack the new blood cells.

Different blood types might be physically incompatible, but there is no scientific evidence that people with opposing blood types don’t get along, or that blood type affects a person’s personality or abilities. Even in Japan, the idea is more of a superstition, says Robertson. “People wouldn’t make any major life decisions based solely on blood typing,” she adds.

web extra

Play an online game where your knowledge of blood types will help you perform a simulated blood transfusion at: www.nobelprize.org /educational_games /medicine/landsteiner/ readmore.html

nuts & bolts


A chart called a Punnett square helps determine the types of traits an offspring can inherit. The letters on the outside of the chart represent each parent’s alleles for a particular trait, like blood type. The four inner squares are filled with the parents’ alleles that are listed above and to the left of each box. These combinations show all the possible blood types for an offspring.



In Japan, many people believe a person’s blood type speaks volumes about who they are. Check out these blood facts. Do you see a connection between blood type and personality?


Even animated characters are given blood types in Japan. Yugi from the cartoon Yugi-Oh is Type AB


Japanese baseball cards list players’ blood types along with their batting averages.



What’s Your Type?


* A person can donate blood every 56 days. That’s because it takes up to eight weeks for the body to remake lost red blood cells.

* Dogs have 13 different blood types, and cats have three.


* People with blood type O are called universal donors. That means they can give blood to a person of any blood type. Why do you think that’s possible?


MATH: Have students turn to page 9 and use the data from “Percent of Population With Each Blood Type” to create two pie charts–one for the U.S. and one for Japan.


* Find out the history of blood research at this PBS Web site: www.pbs.org/wnet/redgold/

* Students can learn more about genetic inheritance by completing the interactive Punnett Square at: www2.edc.org/weblabs/Punnett/punnettsquares.html


DIRECTIONS: Match the word(s) in the left column

with the correct phrase in the right column.

–1. genes a. forms of a gene

–2. alleles b. infection-fighting cell

–3. platelets c. oxygen-transporting cells

–4. plasma d. molecules that determine blood type

–5. red blood cells e. factors that help blood clot

–6. white blood cells f. fluid that carries blood cells

–7. antigens g. units of hereditary material

–8. antibodies h. proteins that help the body attack foreign



1. g 2. a 3. e 4. f 5. c 6. b 7. d 8. h

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