This is Hayashi Osamu, a cram school teacher who became famous for a commercial in which

he says "ja itsu yaru ka？ima desho!"

That's easy for him to say because Hayashi Sensei here is blood type O and as we know

from the 2013 anime "ketsuekigatakun" or “Blood type kun,” blood type O people have great

focus and can stay up all night studying.

You see, in Japan, blood types are sort of like zodiac signs.

Many people believe that blood type affects personality and can determine things like

the compatibility of a marriage partner.

And, this idea has been widespread since at least the 1970's when journalist Nomi Masahiko

made it popular.

Blood type is more likely to be brought up by women when on the topic of romance, but

it's not uncommon for blood type to appear in the media and many other places.

This is famous singer Nishino Kana's 2015 song about blood type A people.- “Datte

watashi A gata da shi, yappari are kore to shinpai…”

One Japanese television show aired an experiment to see how kids would react when a “substitute

teacher” dropped a vase that the kids were told was very important.

They saw that blood type A kids right away told on the substitute teacher, type B kept

the secret, type O also told on the sub, and AB promised to keep it secret but then ratted

the sub out anyway.

In 1990 the Asahi newspaper reported that Mitsubishi Electronics created a small team

composed entirely of blood type AB people, thanks to their “excellent creativity and

planning skills".

In 2011, ex-Minister Ryu Matsumoto, famously conducted himself in an unprofessional way

that led to his resignation.

He blamed the rude behavior and abrasive remarks he made towards two governors on the fact

that he was blood type B. "B-gata de tanrakuteki na tokoro ga atte" That same year, an issue

of Asahi Newspaper talked about how some new graduates were worried that they were being

discriminated against during hiring processes for being blood type B.

It's not particularly common, but people can sometimes be asked what their blood type

is during a job interview, and on some companies' job application sheet, there's even a field

to fill in your blood type.

One twitter user wrote in 2015 that one of his work superiors said that “blood type

O people are usually irresponsible so I don't want to hire them.”

Now let me be clear that I'm not trying to present this as a big societal “problem”

- the point of these examples is simply to illustrate how widespread the concept is in

Japan.

According to data from 2016, somewhere around 40% of Japanese people believe that blood

type contributes to your personality, but what was most surprising to me was that: According

to a 2017 survey from an online community exclusive to doctors called medpeer, 38% of

doctors thought that blood type affects personality.

Let's first take a quick look at the history of this.

In 1901, Austrian Physician Karl Landsteiner discovered blood types and we now can type

blood based the antigens on the blood cell.

Simply put you are A, B, AB or O depending on if you have A antigens, B antigens, both

antigens or neither of the antigens.

By the way, ABO is just one of many blood grouping systems, but it's what we'll

focus on for this video.

In 1910, German scientists Ludwig Hirszfeld and Emil von Dungern demonstrated that blood

type is an inherited trait, which was recognized as a huge milestone for human genetics.

Around this time, it was found that Japan had twice as many blood blood type B people as did Europeans.

Emil von Dungern made the baseless and unclassy comment that blood type B people, and therefore

Asians with their higher percentage of blood type B people are inferior.

Other researchers including Ludwig Hirszfeld had also made negative comments about blood

type B people.

This inflammatory commentary is what caused professor Furukawa Takeji to begin investigating

how blood type affects personality.

He wanted to prove that there is nothing wrong with the character of blood type B people.

He started his work by analyzing 11 of his relatives.

He found that blood type A people were shoukyokuteki which translates to “inactive,” or “passive.”

The blood type B and O people were sekkyokuteki which means “positive,” or “assertive.”

This encouraged Furukawa to go on and look at colleagues and students as well, investigating 319 more people.

His results were presented in a 1926 paper titled “Research on Temperament due to blood

type” he came up with these traits for each blood type:

Then, In 1931 Furukawa published a sensational article in the famous economics magazine jitsugyounonihon

titled: "Astonishing new discovery---you can understand career and marriage compatibility

through blood type" But, by 1933 the Japanese Society of Legal Medicine said that there

was no relationship between blood type and personality, criticizing Furukawa's statistical

methods and dismissing his findings .

Public interest in the topic remained for a while, but eventually fizzled out.

Then, about 40 years later, interest in blood type boomed again thanks to journalist Nomi

Masahiko's book “Blood Type Anthropology,” with the subtext: “Become happy by analyzing

your personality.”

In the book he pointed out that a majority of the post war Japanese prime ministers were

blood type O and that many successful baseball players from Japan and Korea were blood type

O or type B.

In Nomi Masahiko's 1978 book “New Blood Type Anthropology,” he discusses some data

from that same year - 1978, from the AIU insurance company.

After looking at 1374 people involved in car accidents across 3 months, they found that

those with blood type O were significantly more likely to be involved in an accident

and blood type A people were less likely to be in an accident.

Blood type O people made up 5% more than expect of the accidents, and blood type A people

made up 4% less than expected.

Initially, this data might seem pretty convincing.

But several years later, in 1995, the story was flipped.

Type O's were exonerated and now type A's were the bad guys.

3234 accidents in Ibaraki across two months showed that type A people were much more likely

to have a car accident and type O people were much less likely to have one.

Despite this inconsistency with the 1978 data, conclusions were even made about which blood

type is more likely to have what type of accident, as is illustrated in this easy to understand

comic.

Just this year, 2018, Takeda Tomohiro published a book titled: “It's really amazing!

Blood types.

The new truth can be seen from statistics.”

In the chapter titled “The mystery of No type A sluggers” he points out that all

of the top ten Japanese home run batters and top ten batters with the most hits are either

type B or O.

This might sound like impressive data, "Kore chotto hottokenai data desu ne."

But then again, this is looking at only 20 people.

When you look at the distribution of blood types across the 786 players in the 12 teams

of the Japanese pro baseball league, it is hardly different from that of the national

blood type distribution.

Let's look at some science on what we're confident that blood type does have bearing

on.

There's a lot of research showing blood type does affect your health in several ways.

But…

Blood type O's get most of the perks.

They are less likely to get pancreatic cancer, are less likely to get Malaria, are less likely

to get diabetes and are less likely to develop cardiovascular disease and cognitive decline

in old age.

Type O's can thank lower levels of von Willebrand factor, a blood clotting agent for their protection

against heart disease and cognitive decline, but this also means they are more likely to

die from severe trauma.

You may have heard of the book “Eat right for your type” - "Now did you ever think

your blood type has anything to do with your diet?

Well this doctor says that it does."

author Peter D'Adamo claims that your ticket to good health is eating in a way that is

suitable for your blood type.

He provides several lines of reasoning to back up his claims which I may discuss in

another video, but this blood type diet of his seems to be like the diet version of the

Barnum effect.

The barnum effect is where someone will be given a fortune or description of their personality

based on their star sign or blood type and the person may say it sounds very accurate-

it sounds just like them.

"I can't believe he analyzed me so accurately."

"It does feel actually so personal, it's actually quite hard for me to share."

"It's kind of astounding.

I've always believed in something like it, but it also shocks me because I didn't think

it would work so well."

But in reality, the description was vague enough to where it could have applied to anyone.

"Yea, I'm afraid you have all got the exact same reading."

A 2014 study found that the diets found in “Eat right for your type” - the blood

type A diet, AB diet and O diet provided benefits like lowered BMI, waist circumference, blood

pressure, triglycerides and insulin, ...but it didn't matter who followed which diet.

You could be blood type O and still get the benefits from a blood type A diet.

However, D'Adamo claims that “Studies have shown that Type O has a stress response

that centers on fight-or-flight.”

He explains that the neurotransmitter dopamine is converted into the neurotransmitter norepinephrine

by an enzyme called dopamine beta-hydroxylase, and that blood type O people have higher levels

of DBH, so they are prone to anxiety from increased levels of norepinephrine.

Higher levels of norepinephrine apparently also causes a tendency towards anger and aggression.

Hence, this is why he recommends type O people to do vigorous exercise and eat a lot of protein

because that will block the enzyme DBH.

In the book, there are no reference numbers next to his claims, and “Appendix G: The

Scientific Evidence” didn't have any information on where he got this dopamine beta-hydroxylase

idea, but I went ahead and looked into it and found a paper by a Donna Hobgood under

“Medical Hypotheses”

She explains that the gene for the enzyme we just discussed - dopamine beta hydroxylase

is on chromosome 9q34 and is in tight linkage disequilibrium with the ABO blood typing gene.

This might have been what one of the Japanese doctors in the earlier mentioned medpeer survey

was referring to when he said that the reason he believes blood type is related to personality

is that “He had heard that the gene for blood type and personality factors are close

to each other on DNA.”

Hobgood says in her paper that “low activity DBH would relate to impulsive behaviors while

high activity DBH would relate to persistent behaviors.”

Then, in 2015, inspired by the hypothesis presented by Hobgood, Japanese researchers

investigated “ABO Blood Type and Personality Traits in Healthy Japanese Subjects.”

The results of the study showed significant differences in persistence scores, showing

that subjects with the blood type A allele were more persistent.

Though the authors were careful to say that this should be considered preliminary results

and that this data are inconsistent with several other previous studies.

In contrast, a 2014 paper looking at 10,000 people from both Japan and the U.S. found

that blood type explained “less than 0.3% of the total variance in personality.”

The paper is titled “No relationship between blood type and personality: Evidence from

large-scale surveys in Japan and the US”

So, we're hardly at a point where we can make any worthwhile conclusions about a person's character based on their blood type.

Now, With all this said, couldn't there be something to this blood type personality thing?

After all, the reason some people get invested in this idea is because they really identify

with the description for their blood type.

But, that sounds a lot like the Barnum Effect.

And, another factor in this could be that it's an example of a self fulfilling prophecy

- if someone is often told from a young age that they must be the unique and artistic type because they are blood type AB, then they might start to view themselves as unique and artistic.

Or, if you have a giant “B” stuck to your shirt, you might act a little more like a type B person.

But then again, Maybe the type A blood in me is making me overly skeptical.

While it's hard to actually make use of this information about blood type, hopefully this

was a decent exercise in critical thinking.

If you want to further develop your critical thinking, then I really recommend checking

out out Brilliant.

It's a problem solving website that teaches you to be more analytical.

They take complex concepts, break them down into bite sized nuggets, and guide you to

think and apply your knowledge, so you can build a framework of understanding.

For example, in their Science Essentials course, they explain the story of how Barry Marshall

proved that peptic ulcers are not the result of stress and spicy foods, but the bacteria

H. Pylori.

This is unfortunate for blood type O people as they seem to have a higher chance of getting

it.

In the course, they use this example to not only explain the concept of empirical skepticism,

but also encourage you to think for yourself about why Barry Marshall confidently arrived

at his conclusion - so confident that he actually drank H. Pylori to get an ulcer and prove

his point.

It's good to keep your critical thinking sharp so you can keep yourself safe from flimsy

logic like what we saw in the development of the blood type / personality theory.

So make sure and check out brilliant.org/WIL/ and sign up for free.

The first 200 people that go to that link will get 20% off the annual Premium subscription."