5. Supertasters
People who experience taste with greater intensity than the rest of
the population are called supertasters. Having extra fungiform papillae
(the mushroom shaped bumps on the tongue that are covered in taste buds)
is thought to be the reason why these people have a stronger response
to the sensation of taste. Of the five types of taste, sweet, salty,
bitter, sour, and umami, a supertaster generally finds bitterness to be
the most perceptible.
Scientists first noticed the differing abilities of people to taste a
known compound when a DuPont chemist called Arthur Fox asked people to
taste Phenylthiocarbamide (PTC). Some people could taste its bitterness;
some couldn’t – whether people could depended on their genetic make-up
(a variant of this test is now one of the most common genetic tests on
humans). While about 70% of people can taste PTC, two thirds of them are
rated as medium and only one third (approximately 25% of the wider
population) are supertasters.
Supertasters will often dislike certain foods, particularly bitter
ones, such as brussel sprouts, cabbage, coffee, and grapefruit juice.
Women, Asians, and Africans are most likely to have the increased number
of fungiform papillae that make them supertasters.
4. Absolute pitch
People with absolute pitch are capable of identifying and reproducing
a tone without needing a known reference. It is not simply a better
ability to hear but the ability to mentally class sounds into remembered
categories. Examples of this include identifying the pitch of everyday
noises (e.g. horns, sirens, and engines), being able to sing a named
note without hearing a reference, naming the tones of a chord, or naming
the key signature of a song. Doing any of these is a cognitive act – it
requires one to remember the frequency of each tone, be able to label
it (e.g. ‘A’, ‘C#’, or ‘F-flat’), and sufficient exposure to the range
of sound within each label. Opinions vary as to whether absolute pitch
is genetic or a learned ability that is strongly influenced to one’s
exposure to music at crucial developmental stages – much like how a
child’s ability to identify colors by their frequency depends on the
type and level of their exposure to it.
Estimates of the portion of the population having absolute pitch
range from 3% of the general population in the US and Europe to 8% of
those (from the same areas) who are semi-professional or professional
musicians. In music conservatories in Japan however, about 70% of
musicians have absolute pitch. Part of the reason for this significantly
larger percentage may be because absolute pitch is more common among
people who grew up in a tonal (Mandarin, Cantonese, and Vietnamese) or
pitch accent (Japanese) language environment. Absolute pitch is also
more common in those who are blind from birth, have William’s Syndrome,
or have an autism spectrum disorder.
3. Tetrachromacy
Tetrachromacy is the ability to see light from four distinct sources.
An example of this in the animal kingdom is the zebrafish (Danio
rerio), which can see light from the red, green, blue, and ultraviolet
sections of the light spectrum. True tetrachromacy in humans is much
rarer however – according to Wikipedia only two possible tetrachromats
have been identified.
Humans are normally trichromats, having three types of cone cells
that receive light from either the red, green, or blue part of the light
spectrum. Each cone can pick up about 100 graduations of color and the
brain combines colors and graduations so that there are about 1 million
distinguishable hues coloring your world. A true tetrachromat with an
extra type of cone between red and green (in the orange range) would,
theoretically, be able to perceive 100 million colors.
Like supertasting, tetrachromacy is thought to be much more common in
women than men – estimates range from 2 – 3% to 50% of women.
Interestingly, colour-blindness in men (much more common than in women)
may be inherited from women with tetrachromacy.
2. Genetic Chimerism
In the Iliad Homer described a creature having body parts from
different animals, a chimera, from this mythological monster comes the
name of the genetic equivalent – chimerism. Genetic chimerism, or
tetragametism, in humans and other animals happens when two fertilized
eggs or embryos fuse together early in pregnancy. Each zygote carries a
copy of its parents DNA and thus a distinct genetic profile. When these
merge, each population of cells retains its genetic character and the
resulting embryo becomes a mixture of both. Essentially, a human chimera
is their own twin.
Chimerism in humans is very rare; Wikipedia states that there are
only about 40 reported cases. DNA testing is often used to establish
whether a person is biologically related to their parents or children
and can uncover cases of chimerism when DNA results show that children
are not biologically related to their mothers – because the child
inherited a different DNA profile to the one shown by a blood test. This
is what happened in the case of Lydia Fairchild: DNA tests of herself
and her children led the state to think that she was not actually their
mother.
People born with chimerism typically have immune systems that make
them tolerant to both genetically distinct populations of cells in their
body. This means that a chimera has a much wider array of people to
choose from should they need an organ transplant.
1. Synesthesia
Imagine consistently associating numbers or letters with certain
colours, or hearing a specific word which triggers a particular
sensation of taste on your tongue. These are two forms of a neurological
condition called synesthesia. Synesthesia is when stimulation of a
particular sensory or cognitive pathway leads to an involuntary (i.e.
synesthesia is not learnt) response in other sensory or cognitive
pathways.
Synesthesia is most often genetic and the grapheme (letters, numbers,
or other symbols) to colour form of synesthesia is the commonest. Other
synesthetes can experience special-sequence synesthesia (e.g. where
dates have a precise location in space), ordinal linguistic
personification (when numbers have personalities), or sound to colour
synesthesia (where tones are perceived as colours).
Although synesthesia is a neurological condition it shouldn’t be
thought of as a disorder, because generally it does not interfere with a
person’s ability to function. Most people are not even aware that their
experiences of life elicit more sensory responses than other peoples
might and the ones that are rarely consider synesthesia to have a
negative impact on their lives.
Predictions of the percentage of people with synesthesia vary widely,
from 1 in 20 to 1 in 20,000. Studies from 2005 and 2006, using a random
population sample, suggested 1 in about 23 people have synesthesia.
Examples of people with synesthesia include the author Vladimir Nabokov,
composer Olivier Messiaen, and scientist Richard Feynman. Daniel
Tammet, who is mentioned in the next section of this list, is a
synesthete (in addition to being a mental calculator) who sees numbers
with shapes and texture.
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