Poets may say that it is something that cannot be put into words. Philosophers could speculate on what it means to truly love someone. But despite the typical Valentine’s Day decorations, love comes not from the heart – but from the brain.
When two people begin falling in love with each other, the brain undergoes chemical changes that affect behavior, thought processes and some things so subtle that they often go unnoticed.
The goal of love, whether humans like to admit it or not, is to find a mate and reproduce, passing along the genetic code of each parent to the next generation.
Joseph Ross, an assistant professor of biology at Fresno State, said that there is a cost to sex, though.
“We could be more fit — in the evolutionary sense — that is, we could pass our genes on to more offspring, if we didn’t have to sexually reproduce,” he said.
Some organisms can reproduce asexually, or without a partner. But sexual reproduction, as is the case with humans, does have its perks.
“Sexual reproduction is beneficial because it brings together new combinations of genes – it creates diversity,” he said. “From the evolutionary standpoint, that’s really beneficial because if the environment changes, you would be more healthy if you had a particular set of genes that let you respond, then that variation is beneficial.”
Though genetics are not a biological process exclusive to humans, the complexity and intensity of the experience of love is unique, said Martin Shapiro, a Fresno State biopsychology professor.
Love is a crazy thing
Shapiro said that while falling in love can be an intimidating experience, our brain has ways to overcome the fear.
“There’s a scary thing about opening yourself up to somebody, connecting with somebody, staying with somebody for a long time – that’s a scary thing. So how do you overcome those scary things?”
As it turns out, love is a crazy thing – literally.
“In order to overcome those scary things, the brain chemistry has to change a little – you have to get a little crazy,” Shapiro said. “You have to get a little obsessive. You have to get a little addicted. You have to do all those things to do a very scary thing – and that’s to bond with somebody, especially for a long time.”
Peggy Gish, a Fresno State health lecturer who teaches a human sexuality course, said that while love is a very complex concept, and that there is much variation in what determines how, when and who we fall in love with, that it is grounded in a biological drive.
“Now we know much more about brain chemistry,” Gish said, “that when you are falling in love, for many people, their brain is bathed in different chemicals.”
This is a process that humans often cannot control. The brain releases neurotransmitters, particularly dopamine and noradrenaline, which are chemicals that affect how it is functioning.
Though the increase in levels of dopamine is involved in the process of attraction, it is also found in people that are addicted to everything from cocaine to slot machines, Shapiro said.
In research of addiction and love, scientists found that people who are just falling in love show the same type of brain activity as people who are addicted to alcohol or drugs, or even certain food or behaviors, like gambling.
“They become, in a sense, addicted to this person,” Shapiro said.
In describing the different types of love that humans experience, Gish said that every person has their own way of seeking a mate.
“For some, it’s very much a thing of physical attraction,” she said. “Other people, instead of the lust and something from their body, they use their head and they’re very logical.
“It’s not just the romantic, and those that are more practical, but there’s also the players out there. They’re the love junkies. They want to feel that chemistry of attraction, and then it gets old, and then they want to feel it again with somebody else,” Gish said.
This rush comes from chemical called noradrenaline, which is very similar to adrenaline. It has a lot to do with arousal and excitement. It is also seen at heightened levels in people beginning to fall in love.
This causes what is known as the “honeymoon phase” – where people seem obsessed for a period of time after starting a relationship.
“When you first fall in love, your brain starts doing things that are very similar to some other psychological disorders,” Shapiro said. “People literally get love-sick.”
Another neurotransmitter that contributes to attraction is serotonin. This chemical is found to be at low levels in people who have depression or obsessive-compulsive disorder (OCD), Shapiro said. In this way, obsession is a part of falling in love.
“The idea is that when we’re falling in love, we might keep in our brains the person we’re falling in love with or infatuated with all the time,” he said. “We’re obsessive about them. There’s some chemicals to back that up.”
“It’s almost comical if you go to a party where new lovers are there, and really still so early in their relationship. It’s like they’re on cocaine or something,” Gish said. “They’re just full of stimulation. They can’t get enough of each other.”
These chemical levels even out and the brain return to normal when the honeymoon phase is over – but what makes us stay with that person?
After the honeymoon
“There’s got to be something that keeps people together after a period of time, too,” Gish said.
Once again, biochemistry plays an important job in this as well.
The levels of two more hormones, oxytocin and vasopressin, begin to increase in people who are in long-term relationships.
In a lab experiment, male voles (mouse-like rodents) were injected with vasopressin. In certain species of voles that typically don’t mate for life, this artificial increase in the hormone caused the males to want to bond forever, Shapiro said. The same applied with oxytocin in female voles.
“If you block those hormones, even in voles that like to bond for life, they separate. They don’t want to bond,” he said.
Oxytocin is also released during childbirth, so it is thought that it may be present to form a bond between mother and child, Shapiro said.
“They’re also released during orgasm,” he said. “So maybe there’s some kind of bonding going on during sex.”
While selection of a partner is an experience that has many factors to it, there are some small clues that humans may or may not always be aware of, but still influence the decisions made on a subconscious level.
Just as some species of plants and animals release pheromones to attract their mates, humans also have a method of attraction that plays to the senses – smell.
Love is in the air
The human leukocyte antigen (HTA) gene is a hormone that is released from the glands that gives an indication of what type of immune system a person has, Shapiro said.
In a famous lab experiment, participants were asked to wear a T-shirt for two days, sleeping and sweating in it. The shirts were then collected and placed in containers. Other participants of the opposite sex were asked to rank the shirts in order of which they thought smelled best.
The data showed that people favored the shirts of the participants that had immune system that were different from their own, based on blood tests that had been taken prior to the experiment.
Essentially, we are attracted to someone’s smell when it gives an indication that their immune system is different from that of our own, Shapiro said. “You don’t want a redundant mate for an offspring. So, you can sense, in a way, their immune system.”
The brain causes subtle changes in the way the body is functioning when chemically aroused – an increase in heart rate, dilated pupils and sweaty palms. There also are facial micro-expressions that let people know, often subconsciously, that a person is attracted to them.
Messing with the formula
Shapiro said he worries that people do things that can mask or change these small hints that let each other know they are attracted. Perfume can mask the effects of pheromones. Botox can decrease the use of facial muscles and therefore micro-expressions.
But perhaps the most prevalent culprit of modifying the natural processes of love and attraction is an increase in the use of antidepressants, Shapiro said.
Antidepressants help people with OCD or depression by facilitating the brain to be able to absorb more serotonin. However, low serotonin levels are also a part of the attraction and bonding mechanisms of the brain, by making us “crazy” and “obsessive.”
Shapiro said, “Well, what if then you want to bond with somebody, and you want to go through that whole process, and you don’t get a little crazy? Does that reduce your ability to fall in love?
“For most people, the act of falling in love and bonding with somebody for a long-term relationship is both very cool, very scary, and sometimes very difficult, and if the brain isn’t allowed to get those reactions then there might be some problems.”
Gish said that problems might also arise from people who are not fully informed about sex and relationships, which can lead to insecurity.
“That insecurity breeds one of two extremes, it seems,” She said. “Either you need to go out there and prove yourself sexually, because you don’t have the answers from anyone else, or you feel so intimidated you kind of withdraw from something that’s so natural.”
What makes us human
In the end, love cannot be boiled down to merely chemicals and genetics – but that is not to say they do not play a part in it. The human brain is complex; therefore the love that comes from it is bound to complex as well.
“What makes us human is our ability to love, and if ever we deny that and try to minimize that desire by thinking we can do well in isolation, that we don’t really need other people, we’re fooling ourselves,” Gish said. “I don’t see our drive for love just being an antidote for loneliness. I think it’s more powerful than that. I think it’s that our brains are just wired for it.”