Oxytocin: The Love Molecule?

Nov 19 2009 Published by under Behavioral Neuro

And now Sci can finally get down to writing the hefty post in the oxytocin series, what she likes to call the effects on the soft stuff. The emotions, memory, trust, that kind of thing. She didn't know if she'd make it, for verily, this little grad student hath earned her ramen this day in looooooong experiments and time slaving away in the salt mines laboratory. But she is here! Her ramen is eaten! And it is TIME!
Oxytocin: Effects on the State of Love and Trust
aka "The LOVE molecule?"

(Right now, this is Sci's definition of love)
Sigh...Sci has heard so many people call oxytocin "the love molecule". Almost as many people as she has heard call dopamine the "reward molecule", or serotonin the "happy molecule". Based on the previous examples, Sci now officially reserves the right to call norepinephrine the "holy s**t we're going to DIE" molecule.
What do all these have in common? They are all SO MUCH MORE COMPLICATED THAN THAT. But for now, we're just going to stick to oxytocin. The "love molecule"?! You don't know the half of it!

I'm going to have to divide this one up into several subheadings, because the effects that oxytocin has on social interactions in humans (I'm leaving out the voles for this one, far too needlessly complicated), are really THAT diverse.

To begin.
Facial Recognition

(A facial recognition task)
"Facial recognition?" You say. "That doesn't sound like love or emotion or anything!". Well, no. Until you find out that oxytocin influences the recognition of faces that are exhibiting specific emotions. Some studies have found that increasing oxytocin in humans (they usually use a nasal spray) increases memory for faces flashed across a screen. Interestingly, some studies have found that this works particularly well for angry or neutral faces, with happy faces unaffected, and some studies say it's just faces in general. This may mean that oxytocin is particularly important for recognizing facial emotions. In fact other studies have found that increasing oxytocin increases the amount of time your eyes focus on someone else's. This isn't just good for staring into people's eyes, it's also good for detecting their emotions, and for facial recognition. And remembering what emotion that face was just expressing is pretty important in terms of social networking.

Specifically memory for faces (very important for remembering social stimuli), and memories that are positive! Studies have shown that oxytocin can affect how often you determine that the faces you see are positive ones, and how well you remember them, without having any effects of oxytocin on your mood. Oxytocin can also influence how you judge people, possibly causing you to judge them more positively and thus remember them more positively. This could be really important for figuring out whether you've seen this person before and whether they are socially approachable (depending on their mood).

Most people think they are very objective about who they trust, basing it on past behavior of the person towards them and others. And of course this does play a role. There are lots of studies showing that humans (and other primates) will figure out who can be trusted and punish those who violate their trust. But hormones, especially oxytocin, also play a role in who to trust, just by the look on that person's face. For example, giving people oxytocin makes them rate the photos they see of normal people as being more trustworthy (and also more attractive), possibly encouraging you to judge other people more positively.
But don't worry, you don't just blindly trust people. There are apparently no effects of oxytocin on trust-related behavior when your trust is violated several times. But the hormone may still make you see people as being more trustworthy (before they go and violate your trust, and then you learn), and may even promote your ability to forgive them (The title of that one is good "Fool me once, shame on you, fool me twice, shame on oxytocin").
Pair Bonding

Well, as you may know from previous posts around here, oxytocin is an important molecule for pair bonding and social behavior in female voles (dangit! I swore to myself I wouldn't mention the voles! Sigh...once was enough...). But oxytocin is also important in pair bonding and trust behavior in humans, in both males and females. As you saw above, oxytocin promotes positive memory formation and trust, both of which will enhance "affiliation" which is how much time you want to spend around the other person (in both social and romantic situations). Oxytocin may also be able to help during things like conflict. Oxytocin has been shown to increase positive communication during conflict and decrease cortisol levels (a sign of stress) presumably making the conflict a little easier to resolve. This isn't just for couples, it can also affect how stressed teenagers are, and how well they are bonded to their parents. And of course we know that oxytocin increases during sexual arousal and spikes at orgasm, so it's possible that those increases in oxytocin might have something to do with pillow-talk.
You know, when you look at ALL that oxytocin does (contractions during labor, sexual arousal, lactation, orgasm, trust, facial recognition, influences memory formation, pair bonding, and probably there's more) you have to realize that oxytocin isn't the "love molecule". It's just so much more COMPLICATED than that. You might get a little closer calling it the "trust molecule", but that doesn't even begin to cover the physical aspects as well. When in doubt, just call it OXYTOCIN.

10 responses so far

  • John M says:

    Any idea which molecule(s) caused two typos in the first two "oxytocin"s in the blog? :-))

  • DrJohn says:

    Interestingly, your definition of love happens to match perfectly with mine.

  • Scicurious says:

    John M: The molecule responsible for "tired typing fingers". This molecule is also known as "grad school".

  • leigh says:

    your norepi "____ molecule" characterization about killed me. enjoyed the rest of the post, too 🙂

  • daedalus2u says:

    Nitric oxide, NO is also a “love molecule”.
    Since hemoglobin is the sink for NO, draining out someone’s blood is going to increase the concentration of NO. That is what causes the acute vasodilation of isovolemic anemia. NO destruction is equal to the product of NO and hemoglobin concentration, so at constant production rate, if you decrease the hemoglobin concentration, the NO concentration has to increase to make the destruction rate stay the same.
    Draining someone’s blood out might make them be more attached to you.
    It is my understanding that is the basis for the old joke about God and Adam, where God explains to Adam that He gave Adam two things, a brain to think with, and a penis to love Eve with. Unfortunately, He only gave Adam enough blood to do one of them at a time.

  • And then some men forgot somehow that there was something else they could use this blood for...
    Anyway, if "draining someone’s blood out might make them be more attached to you", then we could explain why vampires are so attractive lately, with all those "Twilights", "True Bloods" and stuff.

  • Anna says:

    What level of Oxitocin in blood is the normal one and can I get tested?
    How much could I get applied if necessary then - what concentration is healthy?

    • Anna, Oxytocin is a volatile hormone. It decays in a few minutes or less. So it's produced right when it's needed. Furthermore it's produced in a very dynamic way. This is suspected to be the reason syntetic oxytocin is painful when given to induce labor. Measuring a normal birth; the levels varies in pulses. Sustained levels in labor might be problem.
      But the weirdness doesn't stop there. Oxytocin is produced when nursing. Oxytocin keep the baby calm (and in some extent the mother too). To help the nursing the nipple should be stiff. The old school chinese medicin drew a weird connection: labor-oxytocin-stiff nipples-cold, so to induce labor those chinese took a bucket of icy water and throw it on the pregnant woman to helpwith the labor!
      The reason why they made this connection is that a very few person can "smell" the oxytocin in the air. I belong to this category of humans, thus my interest for the hormone.

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