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Transcript

Why do humans kiss?

By: Sam Sudish

Theory

The Scientific Process

Humans kiss because it's:

  • Instinctive as a result of evolution and previous behaviour.

  • Creates a feeling of euphoria through a cocktail of chemicals released in the brain, like a natural high.

  • It allows us to establish bonds with a significant other through subconcious exchange of information regarding compatibility.

Hypothesis 1

Hypothesis

1. Instinctive behaviour: Humans kiss because it's instinct. It feels natural because it was a part of our evolution in different forms. The romantic kiss is just the modern form of kiss which has existed throughout stages of evolution for different purposes.

Hypothesis 2

2. Euphoric feeling: It makes humans feel good. So humans kiss because it stimulates their pleasure and reward centre of the brain by causing it to release "happy hormones". This produces a euphoric feeling that we love and we crave more of.

Hypothesis

2

Hypothesis 3

3. Exchange of Information: Humans kiss because it is a way of deepening connection with a partner. This happens when information is transferred through saliva, scent and touch of the lips. Also our brains fixate on the sensation in our lips which makes the happy feeling and bond more vivid.

Hypothesis 3

Research On 3 Hypotheses:

Research and Observation

1. Instinct

Instinct

Nature vs Nurture

A kiss seems to be natural because we see it so much but this isn't a sure conclusion...

90% of cultures kiss and 10% don't due to superstitions and cultural beliefs. According to findings by human ethology expert Irenäus EiblEibesfeldt

If it's natural, that means all cultures would kiss, but this isn't the case. The 10% don't kiss but perform other gestures that mirror kissing like nose rubbing and etc.

Nature vs Nurture

We kiss for the same reason animals "kiss"

If it's instinctive, do animals kiss?

Animals do perform kissing-like behaviours to show affection, supporting that kissing is instinctive. This varies from dogs sniffing to elephants putting their trunks in each other's mouths. The only animal that actually kiss, like humans are Bonobo apes. They even make up after fights with kisses.

We share 98.7% of our DNA with Bonobos

Origin of the kiss

Origin of the kiss

It is widely agreed by scientists that modern day kissing descended from the old practice of premastication food transfer or kiss-feeding. It's similar to what birds do, where the mother chews the food and transfers it to the baby by mouth. It used to be a common practice, even chimps feed this way, hence so did our ancestors at some point. The lip touching became a sign of affection, leading to the modern day kiss.

This idea was introduced in 1960 by British zoologist and author Desmond Morris

Euphoria

2. Euphoria

Cocktail of Chemicals

What happens in the brain?

The signals sent to the brain when kissing causes the brain to release a mix of chemicals. This mix consists of serotonin, dopamine and oxytocin. They work together to stimulate the pleasure/reward centre of our brain. It creates a good feeling, like a natural high and deepens our connection.

Serotonin

Serotonin

Serotonin produces a feeling of calm, stable happiness and lowers stress. The serotonin released during kissing induces the same feeling someone with OCD gets when everything is perfect.

Dopamine

Dopamine

Dopamine is responsible for the euphoric feeling when we kiss. It leaves us craving more because it feels good. Similar to what drugs like cocaine and heroin do to our brains. This is why kissing is enjoyable for most people, because it stimulates the reward pathway in the brain.

Dopamine is produced in the Ventral Tegmental Area and then released into the nucleus accumbens and prefrontal cortex.

Oxytocin

Oxytocin is involved in social bonding. It's also known as the "love hormone" because it creates feelings of attachment and affection.

According to a 2013 study by the Centre National de la Recherche Scientifique, Bron, France where 20 men with pair-bonds were presented 20 women including their partner following an intranasal OXT treatment. Oxytocin is responsible for solidifying pair bonds because the men found their partner's faces more attractive. Meaning oxytocin made their partner seem more appealing whilst having no effect on the other women's attractiveness. It increases in men during kissing which motivates them to find more pleasure and reward in their partner compared to others, strapping them in for the long run. Meaning kissing encourages men to be attached with their partners long enough to raise a family in a long term relationship, thanks to Oxytocin.

Oxytocin

Intranasal OXT treatment

Sensory information

The brain focuses on the sensation on the lips during a kiss more compared to larger parts of the body due to the high amount of sensory neurons in the lips. The information from the lips, nose, tongue and cheek go the brain which interprets it as temperature, taste, smell and movement information. Some of this information goes to the somatosensory cortex, which keeps track of tactile information in a map of the body. The lips are a significant chunk of this part because of the high amount of sensory neurons. This plays a part in how we percieve our partner subconsciously.

Exchange of information

Mating information

Mating Information

A study in 1995 by Swedish zoologist Claus Wedekind showed that women are attracted to men with the differing major histocompatibility locus (MHC) genes or immunity genes. Women and men were picked based on differing MHC genes. Women were presented shirts worn by men for 2 nights without any cleaning. Then were asked to choose their favourite based on smell. The women chose the shirts of men with varying MHC genes than their own. Since a mix of different MHC genes from parents means a stronger immune system of the offspring, that will be more resistant to diseases.

Pheromones

What does this mean for kissing?

Pheromones are excreted chemicals that have hormonal effects outside of the body on members of the same species. Pheromones are important in animal mating since they convey lots of information about the mate and their compatibility. There is no proof that humans can sense pheromones clearly like animals, but from the results of the study, it is inferred that our nose must have some part to play in choosing mates through pheromones. If this is true, kissing would be a great way to transfer these pheromones and other mating-related information. This means kissing might take place because it is a biological mechanism involved in mate selection.

There Are Many Right Answers

All of these hypothesis are valid since they all have been confirmed by studies. Kissing is complex, and the study of kissing (philematology) has only scratched the tip of the iceberg. A solid answer eludes us but all of these hypotheses have been proved and are a step towards the full reason. Yet not everyone agrees with it all.

Confirmation, Rejection or Revision

Hypothesis 1

Confirmation

Confirmed: The hypothesis that kissing is instinctive is proven by our genetic connectionor DNA smiliarity to animals that practice kiss-like behaviours and our versions of it like kiss-feeding turning into the modern kiss.

Hypothesis 2

Confirmed: The euphoric feeling in the brain during a kiss is undeniable. Numerous studies on the chemistry that goes on in the brain and the parts of the brain stimulated by a kiss have provided a clear conclusion. A kiss does have a feel-good effect that is addictive.

Hypothesis 2

Hypothesis 3

Hypothesis 3

Confirmed: Sweaty T shirt test proves that even subconsiously, we have a mate compatibility mechanism. This explains why kissing is a key tool to exchange information with a partner through pheromones and saliva in order to determine compatibility. It is safe to infer that kissing evolved to be a part of our mate-choosing system.

Curiosity

The Scientific Attitude

The theory that it's the "feel good" effect when we kiss that makes us do so is the most widely accepted and accurate, but is quite shallow. That feeling is nice, but there's got to be more to it than that, since it's such a meaningful part of human romantic interaction. The world is vast, consisting of many cultures with different perceptions of what kissing means. Kissing has been around for thousands of years, so overtime the motive and meaning of a kiss must have evolved. Therefore, kissing must be more than just our urge to chase a natural "high", it has cultural significance as well...

Skepticism

Romantic

Platonic

Though this theory is the most scientifically accurate, it explains only the psychological and physiological process behind kissing that has to do with our brain. Not the behavioural or cultural motives behind it, which stems from our mind. Humans don't kiss exclusively for the feeling of love and affection, it is also a gesture of respect and loyalty in many places around the world. These are emotions that aren't associated with romance in any way, unlike what the theory implies. A kiss on the lips with a romantic partner versus a kiss on the cheek of a friend triggers different neural activity and they both mean different things to us. The former is romantic, and the latter is platonic. A romantic kiss is seemingly instinctive, but kissing as a whole with all its variations, was also developed through evolution of culture. So it's important to look at it from a cultural perspective.

Skepticism

Philematology still has much to discover

Humility

Every scientist doesn't agree on these theories because there are also findings that lead to differing conclusions. For example, some scientists believe that kissing comes from breastfeeding rather than kiss-feeding. So there is no finite answer to why humans kiss because there are so many factors at play. For example culture, upbringing and religious beliefs also influence why we kiss. In Germany alone there are 30 different types of kisses. These things are hard to condense, which is why philematologists have not found a complete reason for why humans kiss.

Confirmation Bias

What is confirmation bias?

The tendency to interpret new evidence as confirmation of one's existing beliefs or theories.

The Risk of Human Bias

Considering the bias

Since these studies were held in europe, it's likely that their conclusions might seem right to them because that's the majority in their area.

For example, since the romantic lip to lip kiss is so common in:

- Western pop culture

- Every day life

it would be easy to assume that all humans kiss. This is not the case as seen as the result of the study which proved 10% of cultures don't kiss at all. So it is important to consider that these theories might not apply to everyone due to the sheer diversity.

Why does it matter?

Movies

Daily Life

Descriptive vs Experimental data

Descriptive: Used to describe events, experience or behaviours and identify links between them. Methods of collecting descriptive data are case studies, naturalistic observations and surveys.

Experimental: Used to determine what's accurate and what isn't and to ultimately develop explanations for things. Methods of collecting experimental data are experiments using the random assignment, double blind procedure and variables.

Importance of Collecting Data

Descriptive data

There is a lot of descriptive or correlative data found through and being applied to philematology. It aids in explaining correlation.

Example:

- Link between bonobos' kissing behaviours and ours, backed by our genetic similarity.

Descriptive data is quite helpful, we have more of it than experimental data. Philematologists need descriptive data to uncover connections between different culture's way of kissing and the reasons. A lab and test room can only explain the physical but people's experiences and the natural world offers a look into the mental part of kissing.

Descriptive

Experimental data

Experimental

Experimental data allows philematologists to collect solid proof for hypotheses. Experimental data has almost fully explained the biological side of kissing.

Example:

- The Intranasal Oxcytocin Treatment study showed that Oxcytocin, released when kissing, plays a role in bonding.

The scientific results are strong proof that kissing's part in pair bonding in humans is one of the reasons why we kiss. Experimental data collection helps Philematologists find causes like these, strong reasons.

Human ethics in philematology

Considering Human and Animal Ethics

The case studies discussed were ethical because:

- The subjects were kept anynonymous.

- Subjects participated willingly and were allowed to leave.

- The experimenters were honest and open, so much so that they shared their findings and motives on the big stage at multiple science conventions.

- No human subjects were harmed

Philematologist Emer Macguire, named the UK's best science communicator winning the FameLab competition.

Animal ethics in phelematology

Animal ethics are observed in phelematology because:

- Laws and regulations were followed when collecting genetic information and etc to be compared to humans. Through simple methods like saliva samples and etc.

- No animals were harmed in any studies, their natural mating behaviour was observed from distance without interrupting them.

Animal ethics

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