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the tongue map if you've ever taken an elementary or high school science class chances are you've
encountered this classic of scientific illustration a diagram of the humans are
neatly divided into zones showing the locations of receptors for the four basic tastes sweet at the
tip salty and sour along the sides and bitter at the back you may even have been asked to
reproduce this map by dripping various substances such as salt water sugar water and lemon juice
onto different parts of your tongue and gotten frustrated it even failed the assignment when the
result of the experiment failed to match up to the diagram making you forever bitter and causing you
to turn your back on the entire institution of Science and miss out on a potentially brilliant
career and the prospect of a Nobel Prize maybe well there's some good news turns out you're right
all along the tongue map a fixture of science textbooks for nearly a hundred years is in fact
just total nonsense not only are the tongues taste receptors not divided into these neat little zones
but we now know that there are in fact more than just four basic tastes furthermore scientists have
known this for nearly 50 years so how then has this patently false map persisted for so long well
it all has to do with an unfortunate scientific misunderstanding in 1901 German scientist David P
haynik published a paper titled the psychophysics of taste in it he described an experiment where
any applied substances representing the four basic tastes it grows for sweet quinine sulfate
for bitter dilute hydrochloric acid for sour and salt for well salty when he did this to
different regions of his subject's tongues in order to determine the stimulus threshold that
is the minimum amount of a substance required for the subject to perceive The Taste for each
region this experiment revealed that the stimulus threshold varied slightly but significantly across
the tongue surface being lower on the outer edges of the tongue and increasing towards the center
the threshold variation was also different for each of the four basic tastes for instance the
threshold for Swede was the lowest at the tip of the tongue and increased moving rearward Hennig
published these results in a handy graph showing the change in sensitivity that is the inverse of
the stimulus threshold to each taste across the different regions of the tongue and there
it remained more than four decades unknown to all but few specialists in the field of psychophysics
fast forward to 1942 and the publication of the textbook sensation and perception in the
history of experimental Psychology by American psychologist Edwin G boring despite his name
boring enjoyed a long and fascinated career in the field of experimental psychology among his
many achievements in 1930 boring popularized a cartoon by cartoon SW Hills that could
either be perceived as an old or young woman with the viewer's brain constantly switching
between the two interpretations boring used the cartoon and others like it to study the brain's
responses to ambiguous stimuli leading to such illustrations becoming known as boring figures
boring also conducted experimental studies on the Moon Illusion their common perception that the
Moon is larger when it's close to the Horizon than when it is higher in the sky as well as
an amusing 1917 experiment in which he woke up sleeping subjects and asked them to guess what
time it was amazingly while boring found that many people could not carry out this task at all
those that could often guessed within 15 minutes of the correct time in sensation and perception
in the history of experimental psychology boring reproduced and reinterpreted The Taste
sensitivity grafts from David haining's 1901 paper unfortunately for boring and millions of
school children over the following Century heinig had committed a cardinal sin of data presentation
he didn't label his graph axes properly this led boring to misinterpreting heinig's data into
fundamental ways first he assumed that the lowest values on the graph represented zero sensitivity
to that particular taste and second he assumed that Haney had measured the change in sensitivity
of each taste relative to other tastes boring's reinterpreted graphs thus gave the impression
that The receptors for each of the four basic tastes were concentrated in distinct regions of
the tongue and that each of these regions could perceive only one taste and not others this
seemed to confirm the findings of another German researcher a Hoffman who in 1875 observed that
the center of the tongue had almost no fungiform papilli the little bumps that cover the tongue and
thus concluded that it must also have no taste buds this flawed perception eventually led to
the creation of the now familiar tongue map with one of the earliest versions appearing in a 1952
article in Scientific American by AJ hargan Smith however it didn't take long as artists to confirm
what generations of exasperated students are long suspected as early as 1974 experiments conducted
by American researcher Virginia Collins revealed that while sensitivity to different tastes do
indeed vary across the surface of the tongue these differences are minor and every part of the tongue
is in fact capable of detecting every taste indeed David haining had drawn this conclusion
nearly a century before not included in his widely misinterpreted graphs was the tongue sensitivity
to the taste of salt which was not found to vary significantly across the tongue's surface in
addition to debunking Edwin boring's conclusions Collins also discovered that taste receptors are
not confined to the papillae and are instead found all across the tongue on the soft palate
and at the back of the throat and even though the epiglottis the flap of tissue that blocks food
from entering the windpipe other researchers have also discovered taste receptors throughout the
digestive tract although these are not capable of producing a conscious sensation of taste and are
like they're used to regulate the digestive process there are plenty of other findings
which similarly debunk the traditional tongue map signals from the taste buds are transmitted to the
brain via two cranial nerves the glossopharyngeal nerve which connects to the back of the tongue and
the Corda timpani which connects to the front if taste receptors were actually arranged as
the tongue map suggests it would follow the damage to the quarter tympani would eliminate
one's ability to taste sweetness however in 1965 experiments by Sergey TR bull revealed that this
was not the case likewise in 1993 researcher Linda bartashirk of the University of Florida discovered
that anesthetizing the quarter timpani did not interfere with the subject's ability to taste
sweetness and they've acted actually caused them to perceive The Taste even more intensely and as
if this wasn't definitive enough both boring and heinig were wrong on yet another count there are
in fact more than just four basic tastes one day in 1907 kikunai Ikeda a professor of chemistry
at Tokyo Imperial University was eating dinner with his family when he noticed something odds
the dashi broth in a soup tasted richer and more flavorful than usual after stirring his
soup for a few moments Akira realized that the flavor enhancement was caused by the addition
of kombu a type of seaweed and katsa bushy dried fish flakes this led Akita to theorize
that there was a fifth basic taste in addition to sweet sour salty and bitter which he dubbed
Umami within a year he succeeded in isolating the kombu from the chemical responsible for imparting
the Umami flavor monosodium l-glutamate better known as MSG in 9 Acadia developed and patented
a process for mass-producing MSG from wheat and soy and founded adrenomoto Co Incorporated the
name being derived from the Japanese for essence of flavor today ajnamoto is a multinational Empire
that employs over 32 000 people and generates nearly 10 billion dollars in annual revenue
while MSG is one of the world's most popular flavor enhancers alongside salt and pepper in
addition to pioneering the mass production of MSG Ikeda also studied other foods to determine
if they also contained glutamate and discovered high concentrations in meat seaweed and tomatoes
this led him to theorize that humans evolved taste receptors for glutamate because they often signal
the presence of protein so a vital component of an Omnivore's diet while for many years the existence
of umami had been hotly debated especially in Western circles it has since come to be accepted
as the fifth basic taste with its perception acting as a signal for the digestive tract to
produce protein digesting enzymes more recently researchers have also posited the existence of a
sixth basic taste stimulated by pure fats however the receptor for this hypothetical taste is yet
to be identified while laboratory tests have revealed that while test subjects can identify
the presence of fat under conditions of forced choice most cannot consciously perceive it as a
distinct taste this suggests that like with the taste buds in the lower digestive tract
our perception of fat may be a case of so-called blind taste today the anatomy of the tongue is far
better understood that in heinig and boring's day most taste buds are clustered on bump-like
structures known as papillae of which there are three basic types button-shaped funk for
Papillion mostly found on the tip and outer edges of the tongue ridge-like circumvallet
papillae mostly found on the rear of the tongue and foliate Villi found in trenches along the
rear sides of the tongue these papillae typically hold around 4 200 and 120 taste buds respectively
with the average human mouth containing around 8 000 taste buds each taste bud in turn holds
between 50 and 100 taste receptors with each of the five basic tastes or six as the case may be
being detected by a different type of recep sector as previously mentioned individual taste buds and
receptors are not confined to the Papillion are found all over the tongue and mouth while there
are receptors for the five basic tastes aren't distributed more or less evenly over the surface
of the tongue meaning that you can perceive sweetness and bitterness just as easily on the
back of your tongue as on the tip and saltiness and sourness in the middle of the tongue as on
the edges indeed from an evolutionary standpoint this does make good sense for example bitterness
often signals the presence of toxins if only the back of the tongue were able to perceive it it
would have placed our evolutionary ancestors at a much higher risk of being poisoned it's
now known that not all animals perceive taste in the same way humans for example evolved taste and
seek out sweetness because sweet food like ripe fruit provided a concentrated source of calories
obligate carnivores like cats by contrast do not eat fruit and thus did not evolve to taste
sweetness this means that while Mr Whiskers may love to lick your ice cream cone when you're not
looking he's probably in it for the protein in the cream not the sugar so in light of all this
contradict evidence why then has the tongue map persisted for so long the most likely explanation
is that we humans like order an organization and the elegant Simplicity of the tongue map appeals
to these innate preferences especially when it comes to the sometimes difficult task of
teaching science to children as Linda Bartok noted in 1993 the apparent Simplicity of the tongue map
has made it to popular laboratory demonstration in children's biology classes the popularity of
this laboratory demonstration is particularly amazing considering that it must fail to produce
the expected results quite regularly however there may still be a grain of truth behind the
discredited tongue map for more recent research has revealed a small but significant variation in
sensitivity to different tastes across the surface of the tongue for example bitter and Umami tastes
as well as the heat generated by capsaicin the active ingredient in Chili Peppers is more easily
perceived at the back of the tongue than the front but again this difference is so small as
to be all but insignificant in everyday life so in conclusion should you haven't to run into your 8th
grade science teacher in the grocery store produce all you can now loudly inform them and the rest of
the Shoppers carefully testing the ripeness of avocados that you were right and they were wrong
and that your failing grade was an affront to the Integrity of the scientific method damn it you
can then watch smugly as their expression growing progressively sour they slowly lay down their own
Army Laden fruit and began to cry salty and bitter tears of defeat all the while while reveling in
the old adage revenge is sweet thanks again to War Thunder for sponsoring today's video remember to
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free days of Premium play and free premium tank as well go check it out and thank you for watching
foreign