What is Love?

And if you feel the need to finish that with “Baby, don’t hurt…” I can’t fault you for that! But in all honesty, what is love? It seems to be this nebulous emotion that we can’t control, so just in time for Valentine’s Day, I thought it was time to do some digging through the primary literature for you guys about what really causes “love.” In the process, I found out that the number one question asked of google, and the question I’m answering today is:

What is Love?

What is love?

We can describe love as anything from a feeling to a biochemical reaction, so today, I’m going to dive into the biology behind love. At some point, maybe I will explore the psychology of love, but for now, let’s stick with my physical sciences background and have some fun. I will also add the caveat that I’ll be talking more about love in the romantic sense, not so much the love you feel for your family, although that’s important too. I’ll also be talking about love in a heterosexual sense from a female perspective, because that’s the category I fall within, but some of these concepts apply in any type of loving relationship.

Love might be an addiction

Yea, okay, you’re probably like “yes, I think about him all the time” but it’s not really an addiction! Well, that might not be the case. A while back, we talked about serotonin in the context of champagne, but it also plays a role in addiction. Scientists are starting to really look into the effects that drugs like cocaine and LSD have on your serotonin levels and the serotonin receptors, or what your body uses to read the serotonin signal in your body. Many drugs, both illegal and prescription, cause a rise in serotonin levels, leading to more happy feelings. Similarly, serotonin levels change in humans when they’re in happy committed relationships. For men, the serotonin levels went down, but for women, they went up, and it was reported that the women in this study were thinking about their beloved 65% of their waking hours! Now, the sample sizes in these studies are super low (like 10 of each gender in each group), but it’s still a fun thought exercise, “am I obsessed with him?”

Love is chemistry

Not only am I talking about the chemistry between two people, but now I’m actually talking about biochemistry. Dr. Helen Fisher has proposed three stages of love:

Lust is the stage that you could call your libido kicking in. Although there are probably environmental factors that come into play here, Fisher focuses on the neurology of it all. Chemically, this stage is driven by hormones. I know, it’s like the middle and high school stages of love.

Attraction is lust’s cooler, older cousin. This is the butterflies stage when you’re starting to feel what we call love. This stage can be broken down into three parts based on the three neurotransmitters that drive the outcomes, adrenaline, dopamine, and serotonin. Adrenaline is the palm sweaty, nerve-wracking reaction you get when you see your crush, dopamine is the stage where you get a heightened sense of the relationship and you get a nice energy boost (since dopamine is a pretty great stimulant), and serotonin is the phase where you start thinking about your beloved all the dang time (see addiction above).

Attachment is the super strong bonding phase. Again, it’s split into two phases named for the chemicals that drive their outcomes, oxytocin and vasopressin. Oxytocin is called the “cuddle hormone” and is also important in mother-offspring attachment, while vasopressin is released after a sexual encounter and is implicated in promoting long-lasting relationships.

Love is affected by scent

This sounds really outlandish, but it’s actually not. Martie Haselton at UCLA studies the major histocompatibility complex and how genetic differences change a person’s perception of attractiveness. People generally rate potential mates as more attractive if their genes for the MHC are different from each other. From an evolutionary biology prospective, having parents with different MHC genes is good because you’re more likely to get two different MHC genes and these genes are super important for a functioning immune system. Interestingly enough, this smell effect is negated, and maybe even reversed, when a woman is on the pill, so if you’re dating while on the pill, you’re more likely to end up with someone who has similar MHC genes to you, but may be dissatisfied with him later on.

Love may be caused by epigenetics

Whoa, don’t leave me yet! I know epigenetics is a big word, but basically, epigenetics is a small subsection of genetics that studies the modification of your DNA and histones (aka your genetic stuff) and the more we study it, the more we’re realizing that what you do not only affects you, but also might affect your children. So basically, science is starting to be able to look at the nature vs. nurture debate and to say, yea, it’s wayyyyy more complicated than just nature or nuture, it’s a lovely mix of the two! So how does this relate to love? Well, Hui Wang and coworkers found that prarie voles, a super monogomous species of rodent, can be temporarily tricked into “pair-bonding” by blocking a specific epigenetic modification site, causing the amount of those “feel-good” chemical receptors we just talked about to go up. This was a similar effect to what they saw with mating prarie voles. What’s more, your mating preference may be dictated by what your grandparents did when they were younger! I feel like epigenetics is a good excuse to NOT stress if you want your kids to be happy and healthy.

Want a bit more info on epigenetics? For more on the potential epigenetics of love, check out this article from What is Epigenetics and if you want more on epigenetics in general and how it might affect gender and identity, watch this very exciting TED talk. Can you tell that I think epigenetics is super cool?


Now that you know the science behind love, don’t you find it more beautiful? Finding your tribe or your person can be really special and make you feel like you have no limits. Enjoy your love and have a happy Valentine’s Day!

Are you in love? Are you doing anything special for Valentine’s Day?

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Allena Mistral

Allena is a long time blogger with a passion for helping people. After a lot of thought, she realized that her best skill was her science knowledge. She started spreading her love of science through Chicistry in 2016.

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