How Science Studies Love

That love inspires art goes without saying. Poets, composers, artists, and philosophers have all explored this powerful human emotion – many producing stunning masterpieces as a result. But can scientists also explore this complex and somewhat intangible thing we call love? The answer is a resounding yes! Here are a three ways researchers have approached the scientific study of love.

Neuroimaging

PET scan of the human brain. Jens Maus (http://jens-maus.de/), Public domain.

Technologies like magnetic resonance imaging (MRI), position emission tomography (PET), and modular quantum brain-sensing let scientists visualize and study the central nervous system. The resulting images are used to assess brain health, diagnose diseases, and even quantify how different activities impact our brains. In the case of love, scientists are using neuroimaging technologies to map the effects of this emotion.

For example, in this 2000 study, researchers from University College London looked at the brains of volunteers who reported being “truly, deeply, and madly in love”. They found big differences when these volunteers looked at pictures of their significant others versus when they looked at friends that were a similar age/sex as their boyfriend or girlfriend. Just seeing their love activated several reward regions of the brain including the medial insula, anterior cingulate cortex, and the dorsal striatum. It also deactivated other regions including the right prefrontal cortex, the bilateral parietal cortex, and the temporal cortices.

Today the science of mapping love is exploding. Current studies look at everything from our brain activity when we see a brand we like to the neural basis of unconditional love. This 2010 review – available for free on Academia – summarizes several such investigations.

Biochemistry

Synaptic vesicles release neurotransmitters, https://www.scientificanimations.com/, CC BY-SA 4.0

Hormones and neurotransmitters are chemical signals that allow different parts of our body to communicate. Scientists have identified around fifty human hormones and over one hundred neurotransmitters. These molecules direct and control thousands of physical and psychological functions – everything from digestion, sleep, and growth to mood and learning. They’re also relatively easy to observe and quantify. Neurotransmitters can be detected and measured using classic micro-dialysis techniques, high-performance liquid chromatography, and fluorescence while hormones are detected and measured using ELISAs, mass spectrometry, and simple chemical tests. Using these methods scientists have amassed a huge body of research detailing the complex chemical changes that occur when we are falling into and out of love as well as when we are in various long-term relationships.

The hormone oxytocin. MindZiper, CC0, via Wikimedia Commons.

One key ingredient in many of our internal love potions? Oxytocin. This hormone plays a fundament in parent-child bonding. Given its potency researchers hypothesized that it was involved in early-stage romantic love. To investigate they measured oxytocin levels in the plasma of 40 single individuals and compared this to oxytocin levels in 60 new couples. They then repeated their measurements 3 and 6 months later. They found that oxytocin levels were much higher in the couples than in the single individuals at all three-time points. They also found that oxytocin levels at the first time point were highly predictive of whether the relationship still existed 3 and 6 months! Read all about the study here or check out this detailed review of the oxytocin here.

Continued research has revealed several other key love chemicals including dopamine, endorphins, testosterone, vasopressin, adrenaline, and norepinephrine. These chemicals interact and change as relationships form and grow. Even with this well-established ingredient list, scientists are finding the chemistry of love to be a complex and promising area of research.

Genetics

Scientists are also studying love from the perspectives of evolutionary biology and genetics. The biological reactions that occur when we fall in love are strong, numerous, and largely universal. This suggests that our species’ capacity for love has been shaped and favored by natural selection. For a deep overview of the role of romance in human evolution check out this 2015 review article.

Using technologies like PCR and sequencing scientists are also studying the specific regions of DNA that may influence everything from who we fall in love with to how often we fall in love. Perhaps some of the most famous genes are the major histocompatibility complex (MHC) genes. These are a set of highly polymorphic genes that code for cell surface proteins linked to our body’s adaptive immune responses. An iconic 1995 study, sometimes known as the sweaty t-shirt study also suggested that these genes may also play a role in sexual mate selection in some human populations. (This is a superb and often used introduction to primary literature study.)

Another group of love genes that scientists are studying is the μ-opioid receptors (MOR) genes. MOR genes code for proteins that promote cell signaling in the brain and spinal cord by forming a complex with opioid neuropeptides. A mutation in this gene, known as the A118G alteration, has been linked to a mixed bag of behavioral predispositions including an increased risk of alcohol dependency, higher sensitivity to social rejection, and an increased likelihood of participating in love relationships.

And More! Clinical Studies, Model Organisms, and Math

Model organism Bombina bombina. Marek Szczepanek, CC BY-SA 3.0.

Neuroimaging, biochemistry, and genetics are just three ways to investigate love. Scientists also use observational and clinical studies – just check out the NIH site and type in “love”. Outside the human world, scientists are also studying sexual selection and conflict in model organisms like Pavo cristatus (peacocks), Bombina bombina (fire-bellied toads), and Poecilia reticulata (guppies/rainbowfish). Even mathematicians are getting in on the action! Check out this study that valiantly attempts to model the dynamic processes of love.

.There’s a lot to be said about introducing topics like biochemistry, neurology, model organisms, and statistics through the rose-tinted glasses of love. And no better time than February. Try one of the studies mentioned above then let us know how it goes in your classroom!

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