Love is a many-facted thing. We pine for it. We write about it. We dream of it. We mourn the loss and yet somehow always seem to wind up with our hearts broken again… Love is rough.
And as much as people claim to know about love we often forget that it’s actually complex, chemical multi-step process. Between Lust and Love there are a lot of steps, and a lot of little glands producing chemicals that make you go DERP! This is a break down for writers who want to know the building blocks of falling in love so they can play with it, tweak it, and use it to their own fictional ends.
The Basics
There is more to life than love or hate. Love comes in many stages, as few as three, and as many as eighteen (if my research is correct). Between those stages are a whole host of variables, outside influences, inner doubts, but the basics of love come down to some pretty simple things. And, really, it’s all chemically induced.
The Science of Lust
The first stage of any relationship is categorized as lust. As writers, this is where you usually start. There are entire genres devoted to the Lust stage of a relationship.
I’d like to say here that the whole, “…eyes meeting across a crowded room and she knew that he was the perfect man…” is a lie, but it isn’t. You won’t get real love from a smoldering gaze, but you can do the basic check for Lust in under 30 seconds.
What happens in the lust stage is that you are identifying the physical markers for an ideal mate. This has nothing to do with sonnets and everything to do with wild monkey sex. In the first thirty seconds your hind brain (the little uncivilized part that wants to throw rough-hewn spears at the cars on the freeway) sums up every new acquaintance as: potential mate, help, rival, useless.
The hind brain is seeking phenotypes (physical markers) that signal a healthy genetic compliment. Both genders look for a balanced and symmetrical face (unbalanced faces are associated with genetic defects).
Popular opinions that say men are only interested in butts and boobs has a grounding in science. Men are hard-wired to look for mates with good childbearing hips and adequate curves on top, a sign that the female in question is physically developed enough to carry a child. Western men also prefer smaller jaws and noses, and larger eyes [reference].
Women are a little trickier. A woman who is ovulating, that is to say a woman who is in prime baby-making condition, will look for a man who is overtly masculine: strong jaw, large muscles, someone that reeks of testosterone. When a woman isn’t ovulating she is more likely to prefer a more feminine man, because the softer individual is regarded to be a better long-term care-giver. Men with more testosterone are considered to be flight risks. [reference].
There’s also pheromones at work here. The smell a person gives off will tell other people two things 1) if they are at a reproductive peak and 2) if the person has a complimentary immune system [reference]. Not an identical set, your siblings should never smell attractive because their immune system is too similar to yours. What your hind brain is searching for is an immune system that is radically different, thus allowing your subsequent child to have a better chance at life.
And that’s in the first thirty seconds!
Remember, this isn’t about love or logic, it’s about getting your gametes into the next generation with the best chance of survival. Your hind brain is all about world domination through gene sharing.
Within the next minute the rest of the brain will kick in and start looking for the social markers we are trained from birth to recognize as being ideal in a mate. Much of what you look for will depend on how your parents raised you. If your father was a loving Daddy who spoiled you rotten the chances are good you’ll find men with similar features very attractive. If Daddy was a drunk cuss who ran out on you, men that remind you of Daddy will get an instant black mark on their record.
Even if they aren’t actively looking for a mate the average person will make a mental note of perceived social status, wealth, and ability to provide within the first few minutes of meeting a new person. While you may never do anything with this information, and despite the fact that your logical mind will probably over-rule much of what you initially think, your first impressions about a person are going to have ties to the evolutionary need to survive and procreate.
Limerence
Now we’re in Lust Part II. This is where your brain settles after the intial introduction has taken place but before any real emotional bonds have formed.
Limerence – a term coined by Dorthy Tennov in 1977 – is defined as: 
“‘an involuntary state of mind which seems to result from a romantic attraction for another person combined with an overwhelming, obsessive need to have one’s feelings reciprocated”
I.E. Madly in Love
This is the stage so many writers ground their plots in. This is the stuff of conflict and romance and desire and passion. This is what drove Romeo and Juliet. This is what makes Pride and Prejudice so funny!
If Mr. Darcy had never entered the dangerous waters of limerence poor Elizabeth Bennett and her sisters would have faded into obscurity. Lydia never would have been rescued. Charles Bingley never would have returned to propose to Jane.
And like all good things that are too good too last limerence has an expiration date. Three months.
On average mad lust will get you through three months of heady love [reference]. Then the feelings fade.
What’s going on in the background is pure chemistry (cue Marlon Brando on the set of Guys and Dolls)…
The poor misguided Scarlett in our video clip was quite wrong about proving love. We can. If you really want to find out if someone is in Lust you just need to check for four little chemicals: adrenaline, norepinephrine, dopamine, and serotonin [reference].
Adrenaline is what makes your heart race.
Norepinephrine is similar to adrenaline and gives you an energy boost while improving your focus. This chemical is also responsible for prompting goal-oriented behavior and obsession.
Dopamine lights up the pleasure and reward center of the brain. This chemical is associated with cravings and addictions. That doesn’t even sound like a good thing, but it’s all part of falling in love.
Serotonin that gives you a happy feeling.
Your body actually rewards you for seeing this person that the hind brain as picked out as an ideal genetic candidate for its plans for world domination. Sneaky brain!
When you see the object of your chemically-driven obsession your pupils widen, making everything look brighter and better. Regular dopamine dumps combined with physical or emotional rewards from the relationship will determine what happens after the first three months.
In most cases the relationship falls apart at three months. As the body becomes accustomed to the chemical dump the rose-tinted glasses fall away and you start to see the flaws. The original spark from the dopamine fades and unless you move to the next stage (attraction) the relationship fails [reference].
But not always. An estimated ten percent of married or committed couples are still in the limerence stage [reference]. Even after decades of monogamous relationship.
Couples that stay in the first stages of love and lust are deeply committed, intense, sexually active (This is not permission to go have sex! Think before you strip!), and involved with each others lives.
Researchers have already proven what all good authors know: Couples that work together fall in love and stay in love [reference].
Stages of Love: Lost and Rough-Hewn Spears
Stages of Love: Attraction and Rejection
Stages of Love: Commitment and Happily Ever After
Writing Realistic Relationships (the basics)