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Kiss &
Tell: The Chemistry of Kissing
Kissing
triggers a cascade of neural messages and chemicals. Of the 12 cranial
nerves that
affect brain function, 5 are at work when we kiss, shuttling messages
from our lips, tongue, cheeks and nose to the brain which grabs
information about the temperature, taste, smell and movements of the
whole occurrence. Research has
shown that that first kiss provides important information about the
status and future of the relationship.
Pheremones
Silent
chemical messengers called pheromones are believed to have sped
up the
evolution of the intimate kiss. Many plants and animals use pheremones
to communicate with other members of the same species. Insects are
known to emit pheremones to signal alarm, the presence of a food trail
and sexual attraction. Whether we humans sense pheremones is a
controversial question since we do not have specialised
pheremone-detectors like rats and pigs. However there are some curious
findings suggesting that we do somehow sense pheremones:
* The menstrual cycles of females sharing a dormitory synchronise
* Women are attracted to the scent of T-shirts worn by men whose immune
systems are genetically compatible with theirs.
Human pheremones may include a compound called androstenol which is found in male
sweat which can boost sexual arousal in women. For the ladies,
female vaginal hormones called copulins
(the names that scientists create!) can raise testosterone levels and
increase sexual appetite in men. If pheremones do play a role in human
courtship, then kissing is an effective way to pass them from one
person to another. Kissing researchers believe that kissing may
have
evolved because it helps humans find a suitable mate. Who said love is
blind?!
The Chemistry
Between Kissers
Human
lips have the slimmest layer of skin on the human body, and the lips
are among the most densely populated area of sensory neurons of any
body region. When we kiss, these neurons, along with those in the
tongue and mouth, rocket messages to the brain and body, setting off
delightful sensations, intense emotions and physical reactions.
Psychologists
Wendy Hill and Carey Wilson compared the levels of two key hormones in
15 college male-female couples before and after they kissed. They also
compared the levels before and after they talked to each other while
holding hands. One of the hormones (oxytocin) is involved in social
bonding, the other (cortisol)
is involved in stress. Hill & Wilson predicted that kissing
would
increase the levels of oxytocin (which also influences social
recognition, male and female orgasm, and childbirth) and that this
would be higher in females, who in the study reported higher levels of
intimacy in their relationships. They also forecast a decrease in
cortisol because kissing is believed to be stress reliever.
However......
The oxytocin levels rose only in the males,
whereas it decreased in the females. This was found whether the females
had been kissing, or whether they had just been holding hands and
talking with the men. The researchers concluded that the females may
require more than a kiss to feel emotionally connected or aroused. It
could also be that they needed a more romantic atmosphere than the
experimental lab in which they were tested. But the cortisol levels did
decrease for both sexes, implying that kissing does indeed reduce
stress.
Kissing is
Addictive
Since
kissing evolved, the act seems to have become addictive. Kissing boosts
brain chemicals associated with pleasure, euphoria and a motivation to
connect with someone special. In 2005 a paper was published in which
brain scans were made whilst 17 subjects gazed at pictures of people
with whom they were deeply in love. The researchers found that there
was a flurry of activity in two brain regions that govern pleasure,
motivation and reward - the right ventral tegmental area, and the right
caudate nucleus. Addictive drugs such as cocaine also stimulate these
reward centres by releasing the neurotransmitter dopamine. Love, it
seems, is a drug for us humans.
That First
Kiss
Recent
research suggests that kissing is a very powerful 'rating' tool. Gallup
and colleagues found that from a survey of 58 men and 122 women, that
59% of men and 66% women admitted that there were times when they were
attracted to someone.....yet their interest evaporated after that first
kiss. The 'bad' kisses had no particular flaws; they just did not feel
right, and the relationship didn't go any further. Talk about the kiss
of death!
Gallup
postulates that kissing conveys subconscious information about the
genetic compatibility of a prospective mate because it helps us rate
potential partners. In a survey of 1041 college undergraduates of both
sexes about kissing, for most of the men a deep kiss was about
progressing to the next level of sex; for women it was about taking the
relationship to the next level emotionally. Apparently, kissing helped
the women not only assess (subconsciously) whether the person would
make a first-rate source of DNA but also whether he would make a good
long-term partner. The locking of lips seems to be a kind of emotional
barometer: the more enthusiastic it is, the healthier the relationship.
Is Kissing
Necessary?
Since
most other animals do not kiss and yet manage to produce plenty of
offspring, then kissing is probably not strictly necessary from an
evolutionary point of view. But did you know that not even all humans
kiss? In
fact, up to 10% of humanity does not touch lips. This adds up to 650
million people worldwide....more than the population of any nation on
earth except for China and India. At the start of the 1900s, members of
some Finnish tribes bathed together but considered kissing indecent. In
1897 it was reported that the Chinese regarded mouth-to-mouth kissing
to be as horrifying as many people now think cannibalism is. And in
Mongolia some fathers do not kiss their sons, but smell their heads
instead.
Are You a
Right-Tilting or Left-Tilting Kisser?
A
study of 124 couples kissing in public places in Germany, Turkey and
the USA found that twice as many tilted their heads to the right
as to
the left before their lips touched. Different theories have emerged
about whether this is an emotional preference or a motor preference,
but this is currently still an ongoing controversy. One group of
researchers claiming it is an emotional preference claim that
right-tilting kissers show warmth and love more than lefties (not true,
not true, I yell!).
So,
the next time you approach lips with someone - hopefully very soon
today - then know that thousands of chemicals, pathways and neurons are
about to be triggered.....Do I need to give you homework this month? :=)
References:
O.
Gunturkun. Adult Persistance of
Head-Turning Asymmetry. Nature,
2003, volume 421, Feb. 13th
K.
Grammer, B. Fink & N. Neave. Human
Pheremones and Sexual Attraction. European Journal of Obstetrics &
Gynacology and Reproductive Biology, 2005, volume 118, number 2,
pages 135-142.
H.
Fisher, A. Aron & L. L. Brown. Romantic
Love: An fMRI study of a neural mechanism for mate choice. Journal of Comparative Neurology,
2005, volume 493, number 1, pages 58-62.
D.
Barrett, J. G. Greenwood & J. F. McCullagh. Kissing Laterality and Handedness. Asymmetries of Body, Brain and Cognition,
2006, volume 11, number 6, pages 573-579.
G.
G. Gallup, S. M. Hughes & M. A. Harrison. Sex Differences in Romantic Kissing Among
College Students: An Evolutionary Perspective. Evolutionary Psychology, 2007,
volume 5, number 3, pages 612-631.
C.
Walter. Affairs of the Lips. Scientific American Mind, 2008,
volume 19, number 1, pages 24-29.
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