forum discussion #29

‘The Science of Kissing’

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Click here to listen to our interview with Sheril Kirshenbaum. She was our guest in this Science Forum discussion.

In her new book, The Science of Kissing: What Our Lips Are Telling Us, science writer Sheril Kirshenbaum explores the evolutionary and cultural origins of kissing and why it makes us feel so good.

Species from turtles to lions have animal versions of kisses. Though we may not recognize the head-tapping and neck-nipping that is sometimes involved as conventional kissing, those animal variants can cement social bonds and resolve conflicts. There are cultural variations on human romantic kissing too. Some involve sniffing, and some biting a partner’s eyelashes.
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Watch kissing-like behaviors in animals:

But it’s no wonder that mouth-kissing can deliver a complex sensory bonanza. Our lips are fine-tuned to feel, thanks to their original job, testing the texture and temperature of food. As we develop, we use our mouths for nursing and, in some cultures, for passing pre-chewed food to infants. By linking lip stimulation with a feeling of love and security, these behaviors may have laid a foundation for romantic kissing later in life.

A kiss also sets off a carnival of brain chemistry. With a new partner, kissing releases dopamine that contributes to that feeling of craving, obsession and desire. Even when the dopamine rush dies down, kissing releases oxytocin, a chemical that can promote trust and bonding. That’s why Kirshenbaum says she makes it a point to kiss her husband every morning. “Kissing is a very healthy behavior,” she adds. “[It’s] something we should all be doing more of.”

  • Do you remember your first kiss?
  • Has a kiss ever changed your choice of romantic partner?
  • Have you experienced a cross-cultural misunderstanding about kissing?

Read our conversation with Kirshenbaum. It’s just below.

Humanoid robots practice kissing: Is this the future of kissing?

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Your Comments

  1. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? SherilK

    The Science of Kissing tells the story of humanity’s most intimate behavior. I’d like to begin this forum by asking readers to rate how significant you consider kissing is in your own relationships on a scale of 0 – 5 (5 = highly significant & 0 = no significance) Please include your gender in the response. It will be interesting to compare forum answers to research conducted on the same topic.

    My hope writing this book has been to encourage readers to think a bit differently about what “science” means and how it relates to all of our lives. Ask me anything and let’s have fun discussing The Science of Kissing!

    • Tres

      Kissing someone allows us to see how sensitive and willing to please that person is – are they willing to continue kissing the mouth until they receive a body language cue from us that it is OK to progress to more intimate contact, or does the person kiss and then just forge ahead, without considering all the little signals being passed back and forth?

      • Tres

        BTW I am a male.

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? SherilK

        Hi Tres,
        I suspected you might be male. According to research in evolutionary psychology, men are far more likely to describe kissing as a means to an end or as a way to determine how a partner might perform sexually. Meanwhile, women seem to place far more emphasis on the act of kissing itself. Of course, there are exceptions.

    • joy

      Kissing is VERY important to me. I am female, age 48, and have been kissing boys since 7th grade! Those boys said I was a great kisser, too, so it’s sad that my husband of 22 years does not think it’s interesting or important or sexy, and tries to make do with an occasional peck on the cheek; when I try to get him to sustain a kiss he is always pulling away like a cat who doesn’t like to be held. I thought ALL people liked kissing! He has social anxiety disorder problems – is that part of it?

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

        Kissing is a behavior that’s a nice compliment between nature and nurture. Even though as humans, we seem to have an instinctive drive to kiss another person, it’s very influenced by culture and our personal experiences so varies tremendously across individuals.

        We also have a tendency to let kissing fall by the wayside in long term relationships once the novelty wears off. But kissing serves to boost an important hormone known as oxytocin, responsible for maintaining the special bond we share with those we love. In this manner, kissing can promote the connection we have with a partner.

      • veli

        I am (male-55) in a similar situation and can totally sympathize with Joy.

      • Dave

        Tres,
        I’m 61 and male. I can remember vividly almost having trouble breathing from the excitement of kissing. After 35 years of marriage my wife still wants to. I watch couples my age and the woman seems to overwhelmingly initiate contact. Is this age or culture related?

    • Kevin

      Kissing-5+
      male, married 35 years.
      There is a very noticable smell to my wife’s face closer to her lips and nose. Not her perfume but her own scent. It has always driven me crazy. Anyway, she says the same of me and my facial smell. (Pheromones?) We both love it and find ourselves inhaling like you describe the eskimos. This makes the kissing, French style and just lips, deeply enjoyable.

      I will say that when I described this to a small group of friends (couples) they did not get it or express the same response.

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

        Humans have scent glands around our faces that our ancestors used for recognition and greeting. Today people continue to express a preference for the scents of their partners and children over strangers. Even though we are not consciously often aware of it, our sense of smell tells us a great deal about an experience and serves to guide us in relationships.

  2. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? David Baron

    Wonderful topic!

    When I was a child, my mother would play a game of giving me “Eskimo kisses,” which involved rubbing our noses. I’ve always wondered: is that really an Eskimo/Inuit practice?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? SherilK

      Hi David,
      Good question. Although popular culture tends to depict rubbing noses, the traditional Canadian Inuit kunik, or “Eskimo kiss,” is a kind of nuzzle-sniff. To properly bestow a kunik, you press your nostrils against the skin of a loved one and breathe in, thereby suctioning the skin of the recipient against your nose and upper lip.

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Elsa Youngsteadt

        Wow. So is a kunik romantic, friendly, familiar or all of the above?

  3. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Elsa Youngsteadt

    Hi Sheril,

    Enjoyed your interview, thanks for being here!

    First of all, your question about rating kissing is actually really hard! I mean sure it’s important, but so are SO many other things! I guess I’ll give it a 3.8? Not sure I could explain that if somebody asked me to…

    And my question for you: I’d love to hear more about the experiments that you did for part of your book, where you took at brain scans of people who were looking at pictures of kissing (right?)

    Thanks!
    Elsa

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? SherilK

      Hi Elsa,
      I’m so glad you’re interested in the experiment because that’s my favorite chapter in the book. I felt that since I had the opportunity to write about science, I wanted to bring readers into the laboratory to discuss what it’s like to design and conduct research as well.

      It’s a bit too complicated to go into the details here, but we are about to submit the manuscript to an open access journal, so hopefully it won’t be long before readers can go online and read all about what we did and conclusions from the primary literature.

  4. Dorit

    Hi Sheril,

    I was wondering how kissing is related to hugging? When kissing lost its popularity, did hugging follow? Does it have the same chemical effects as kissing?
    Also, how are mother-baby kisses related to romantic kisses? they both seem very intense (as opposed to the friendly pecks on the cheek).

    As for your question, I’m female, and I’d give kissing 5, since I can’t imagine a relationship that doesn’t include it. But I’d also give 5 to other components, such as hugging (I’m assuming I don’t need to rank them, but if I do, let me know :) )

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? SherilK

      Hi Dorit,

      The lips are packed with sensitive nerve endings so they are extremely sensitive to touch compared to hugging, but both can serve as an important means to connect. Each fosters some similar chemical responses in our bodies that promote a bond we share with those we care about.

      When a mother/parent kisses a baby, it is among the infant’s earliest experiences with love, security, and comfort. These feelings become associated with lip stimulation and the neural pathways involved may become important later in life with a romantic partner.

    • joy

      I recently heard that a 20 second hug causes the human brain to release dopamine; I wonder if kissing does, too?

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

        Hi Joy,
        Kissing can absolutely spike dopamine, which is part of the reason it feels so enjoyable.

      • Mike Collins

        Hi Joy,
        Am curious how the dopamine release was determined in people–possibly by a brain imaging technique, but it would have to somehow be specific for dopamine, or at least activation of its receptors. Anyway, animal studies, in which a probe sensing different chemicals is put directly into specific brain regions, show that dopamine is like many neurotransmitters, released intermittently (and frequently) in many of those regions. If not released appropriately in the region called the corpus striatum, for example, the person would become rigid and tremulous, as in Parkinson’s. In other subcortical regions it has a role shared with various transmitters in emotional behavior, so an association or link might have been made by some imaging study in that regard that you read about.

  5. David

    Hi,
    General hypothesis: adult humans eroticize female behaviors and body parts that were nurturing to us as infants and toddlers.
    Fact: Over most of history, the transition from breast milk to a more complex diet involved passing of food from parent to child by the mouth, after the parent (presumably mom) pre-chewed it. Yes, there was baby food before Gerber’s.
    Isn’t kissing derivative of that, just as close body contact and stroking may be seen to be?
    Conjecture: in societies that for a long time haven’t shared food that way, kissing may be much less likely to be part of the standard erotic repertoire.
    What do you think?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

      Many anthropologists believe that kissing may be an extension of behaviors such as nursing and premastication (the pre-chewing of food for another individual) during our earliest experiences. These are our first experiences feeling loved, comforted, and secure and involve lip stimulation and movement similar to kissing. So it’s possible that the neural pathways laid down during these significant exchanges with a parent may start the blueprint for kissing a romantic partner later in life.

      It’s also important to include that mouth to mouth kissing does not always occur in cultures that premasticate food and nurse children, so there are exceptions.

  6. Aaron

    I am a 28 year old male. Id have to rate kissing as a 5. In regards to the concept of kissing being a means to an end for men, I don’t think that necessarily describes me. No matter where my romantic encounters end up, or just signs of affection in general, nothing can replace kissing, whether its mouth to mouth, on the cheek, whatever. The background to the Inuit “Eskimo” kiss was very interesting as I have an automatic tendency to sniff my significant other, especially burying my nose in their hair and neck, but couldn’t really explain why I do such a thing. The immune system/smell connection is very interesting and I’m curious if there is other traits that are strongly connected to our smells. Id’ heard long ago that similar chemical make up was important to enjoying the smells of others.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

      Hi Aaron,
      There are most definitely exceptions to the survey results as people vary tremendously on an individual basis.

      There has been a great deal of research on scent preference beyond the major histocompatibility complex research. For example, breath might provide clues about a woman’s reproductive status. There is a lot more in the book and bibliography about this.

  7. Jesse

    Why do some people smell naturally “sweet”? Is it diet-related, is it a cultural thing, hereditary, or is there more to a person’s natural smell?

    Loved the interview, by the way : )

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

      Hi Jesse,
      Thank you. There are many factors involved in a person’s natural scent. Some may be influenced by diet, gender, and /or genetics. This is not something I spend much time on in the book, but it’s a very interesting topic in the literature.

  8. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Rhitu Chatterjee

    Hi Sheril,

    Thanks for taking the time to be here. Something I didn’t get to include in the podcast is how men differ from women in kissing technique. You write that men often prefer sloppy, open-mouthed kisses. Is there an evolutionary basis to it?

    Also, I’m wondering…what’s the single biggest challenge you faced when researching/writing this book?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

      Hi Rhitu,
      It’s my pleasure to participate in the forum! Thanks for having me.

      Yes, there does seem to be a difference in preferences based on gender. Men frequently express they enjoy open mouth kissing while women tend to complain about too much tongue. There may be an evolutionary basis: Men’s saliva contains a small amount of the male sex hormone, testosterone, and women are very sensitive to it. Evolutionary biologists say it’s possible, that after repeated exposure over time, a man’s saliva may serve to enhance a female partner’s libido – which would be to his advantage.

      The greatest challenge was finding the right tone. It had to be enjoyable for broad audiences without being overly technical, while not “dumbing down” the science. Hopefully, readers will like the balance.

  9. Kim

    I am a 22 year old college girl. To me kissing is important in a relationship, I would have to give it a 4 out of 5 on the scale of significance in a relationship. I understand that most people may not have the chances to perfect the kiss, but other factors such as his personality might make up for it. I do agree with the whole when you kiss someone your brain release dopamine which makes us develops trust and bond with the person. I wonder how else can dopamine levels be raised in the human body to make members of opposite sex still stay longer in love.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

      Staying together has far more to do with oxytocin than dopamine. Dopamine is influenced by novelty while oxytocin is associated with a sense of attachment and helps maintain the special bond with those we care about.

  10. Xiaan

    Kissing is very important to me. I give it a 5. Over the years I’ve notice that a good first kiss is a spot-on indicator of future chemistry. A cold, awkward kiss has correlated with low future interest and sexual chemistry. A hot, passionate kiss has correlated with high passion and strong sexual compatibility. A good kiss tells me I will like the smell and taste of her saliva, skin, and body. I know studies have been done on attractiveness and how likely couples are to stay together long term. Have any studies been done on whether a satisfying kisser is correlated to long term relationship compatibility? Or likelihood to have children together? Higher fertility rates? Male, 36.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

      Frequent kissing seems to be correlated with higher stated level or relationship satisfaction, but there hasn’t been much research I know of on specifics. However, scientists have studied several of these factors for couples based on each partner’s major histocompatibility complex (MHC) – a region of the genome that codes for the immune system. People with very different MHC regions seem to fare better in terms of relationship satisfaction, fidelity, and more. Women seem to me most attracted to the scents of men with a distinct MHC from their own and kssing puts two people in very close proximity to sample signals like scent to determine whether to pursue a deeper connection.

  11. Rene Schweitzer

    Hi Sheril and thanks for doing this forum. I’m a female age 37 and rate kissing as a 3 or 4. I was curious about new mothers, infants, and kissing. I know some women who can’t stop kissing their babies and wondered if they feel kissing their newborns is a way to bond with them?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

      Mothers and infants have elevated levels of the “love” hormone oxytocin in their bodies, which is involved in strong feelings of attachment and bonding. Nursing, kissing, and lip stimulation can all promote this chemical.

  12. Karen Jackosn

    I love kissing my husband of 42 years more and more as time goes on. I’d give it 5 out of 5 now, though in the beginning maybe only 2 or 3.

    But I am curious about another kind of important kissing. I have noticed that a few of my close women friends and I will kiss on the lips upon parting or greeting, instead of the peck on the cheek or “near miss” kind of kiss. Is this just a habit of my eastern liberal woman friends? I am happy with it, and curious about it, because it is not overtly sexual, but very indicative of closeness.

    woman, 64

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

      The social kiss may have emerged differently than the romantic kiss. Our ancestors depended on their noses in greeting, recognition, and as a symbol of trust by letting someone get into one’s “personal space.” Anthropologists think that the brush of the nose may have at some point been accompanied by a brush of the lips, leading to the gesture we see between friends.

      But as I wrote earlier, the form that kissing takes between two people is very much influenced by culture and our personal experiences.

  13. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Sheril Kirshenbaum

    Thanks to all who participated in the forum!

    I asked he initial question because research in evolutionary psychology suggests that women seem to place greater significance on the act of kissing itself than men do. Readers responses have been interesting here.

    I’ve really enjoyed exploring some ideas in my book with all of you. Thanks also to PRI’s The World for hosting the discussion!

  14. Hi Sheril,

    I am with a guy who hates kissing, but I love him. So although kissing was of extreme importance to me I got used to not kissing. I don’t know if in the future this will be a problem but for now, I find kissing quite unattractive. I think evolutionary psychology should also consider the causal effect of learning.

  15. Glennda Mirabete

    I don’t find kissing that important, I don’t know. Am I not normal?

  16. A kiss is just something to be enjoyed by both participants…why make a big deal of it and get technical….

  17. Tim Mac

    Kissing is a weapon, because love is a battle field.

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