Science of Love - Cupid's Chemistry

Claire McLoughlin describes the chemistry of love and what happens when we fall in love, including substances that make us feel turned on, the neurotransmitters involved in orgasm...
14 February 2006


Love; what is it, where does it come from and why? What is Love ? The Oxford English dictionary describes love as: an intense feeling of deep fondness or affection for a person or thing and to fall in love as: to develop a great love for. This may well be a basic description of what love feels like, but why do we love, what is passion, and why is intense desire between two people sometimes called 'chemistry'?Heart Box

There are, in fact, three distinct stages of love; each with their own characteristic emotional profile and scientific explanation.

First is lust. Lust is driven by our sex hormones testosterone and oestrogen. These hormones are what get us 'out on the pull'. After lust comes attraction. This is the love-struck phase; the time when we lose our appetite, can't sleep, and can't concentrate. This is what we know as falling in love.

When we fall in love, our palms sweat, we can stutter and become breathless, we can't think clearly and it feels like we have butterflies in our stomachs. This is all due to surging brain chemicals called monoamines. They are called dopamine, norepinephrine and serotonin. Norepinephrine and serotonin excite us, while dopamine makes us feel happy. These love chemicals are controlled by a substance which is also found in chocolate and in strawberries, called PEA or phenylethylamine and it is PEA which controls the transition from lust to love. Similar in structure to amphetamine, PEA too gives us that excitement we crave. Indeed, some people become veritable love junkies. They need a constant love high and go through life in a series of short relationships which crumble when the initial chemical rush wanes. The love junky has another problem too. We naturally build up a tolerance to these chemicals eventually, so it takes more and more to produce that much sought after high. Love junkies, if they stay married, are likely to seek frequent affairs to fuel their need for the chemical love high.

The Chemical Bond The third stage of love is attachment - staying together. Attachment takes over from the attraction stage and is the bond which keeps couples together. After all, we couldn't possibly stay in the attraction stage for ever - we would never get any work done for day dreaming. Two different hormones are important during this phase of love. They are oxytocin and vasopressin.

Oxytocin (the cuddling chemical) not only increases the bond between lovers, but is also one of the chemicals responsible for contractions during childbirth, milk expression when breastfeeding and is released by both sexes during orgasm. The theory goes therefore, that the more sex a couple have, the greater the bond between them. Nice touch Mother Nature.

Vasopressin is the monogamy chemical. Only about three percent of mammals are monogamous; mating and bonding with one partner for life. Unfortunately, humans are not one of these naturally monogamous animals. The prairie vole is however and it is this furry friend which is responsible for our knowledge about vasopressin.

By isolating male voles before and after mating, scientists found that life-long mating could be linked to the action of vasopressin. Before mating, the vole is friendly to male and female voles alike. Within 24 hours after mating, the male vole is hooked for life and defends his partner jealously. The post-coital production of vasopressin is responsible for this amorous behaviour. These little animals also indulge in far more sex than is actually necessary to reproduce and it was considered that the post-coital production of vasopressin (and oxytocin) was responsible for their strong partnership bonds. When given a compound to suppress the effect of vasopressin, the prairie voles lose their devotion to each other and the males fail to protect their ladies from the threat of other males. Perhaps, therefore, we could learn something from the prairie vole. Drop of vasopressin anybody?

Endorphins are also involved in the longevity of love. Endorphins have the same pain-killing and pleasure-delivering properties as their cousin, morphine, without the risk of overdose.

Choosing a Partner Now, when it comes to choosing a partner, are we at the mercy of our subconscious or do we make a more conscious decision?

It is to our advantage to choose a partner with the best possible genes as these genes will be passed on to our children and ensure they are healthy. Therefore, we naturally seek out somebody with an immune system different to our own. Additionally, it is important to find a mate with whose genes are also similar enough to our own to confer a tried and tested immune system. Is this the reason we fancy those who remind us of our parents perhaps? When we are attracted to another person, it could be because we subconsciously like their genes.

Pheromones How do we do this? We seek and sniff out Mr Right! Imagine an invisible overwhelming force which overpowers reason and invites passion. A force which dictates where Cupid's arrow will land. Cupid's chemistry. That's the power of pheromones. Pheromones are 'smellprints', supposedly as unique as our fingerprints. Smell is the most primitive of human senses, and pheromones, present in underarm perspiration, are detected by a small organ composed of a few small pits a few centimetres up the nose. The emotional reaction they provoke can, quite literally, be a 'turn on'!

Therefore, next time you find chemistry with another person, you really have!


When it comes to choosing a partner, are we at the mercy of our subconscious? Researchers studying the science of attraction draw on evolutionary theory to explain the way humans pick partners.

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