CLOSE
ThinkStock
ThinkStock

What Happens to Your Brain When You Fall in Love?

ThinkStock
ThinkStock

Falling in love is one of the best feelings in the world—and humans might not be the only creatures who do it. Pair bonding, the two-by-two partnering of creatures, has been seen across the animal kingdom. Whether or not a nesting pair of robins can be said to truly love each other, we're still awfully interested in why animals might pair off. The tools available to biologists have advanced immensely in the last few decades, and some are using that technology to decipher physiology involved in both pair bonding and love.

Getting In-Vole-ved

To unravel the mysteries behind pair bonding, researchers studied not robins, but voles. Prairie voles and montane voles are closely related rodents with a stark difference in mating behavior: prairie voles form lifelong pair bonds after mating, while montane voles are promiscuous. The work of Thomas Insel, director of the National Institute of Mental Health (NIMH), and colleagues showed that the different mating behaviors can be linked to the hormones oxytocin and vasopressin. Oxytocin stimulates childbirth and lactation, while vasopressin regulates the kidneys and constricts blood vessels. More recent research has implicated the two hormones in many different social behaviors, from working cooperatively to selecting mates to inferring the emotions of others. Oxytocin in particular has calming effects and seems to help build trust between people.

The crucial physiological difference between these two species of vole is in the distribution of oxytocin and vasopressin receptors in the voles' brains. Prairie voles have a higher density of both types of receptors in the amygdala, the area of the brain involved in emotion-related memory formation, and in various parts of the dopamine reward system. Both hormones are released when prairie voles mate, prompting pair bonds to form. When the hormone release is blocked, prairie voles become promiscuous. Perhaps more tellingly, when montane voles are genetically modified to have prairie vole-like distributions of vasopressin receptors, they become monogamous.

Dopamine is an important part of the picture as well. The release of dopamine gives a pleasurable feeling, and is used in the brain to reward behaviors such as procreating or eating a hearty meal. Voles that are made more sensitive to dopamine can develop partner preferences without mating—a friendly encounter will do. Voles whose dopamine receptors are blocked do not form partner preferences at all. Many of the dopamine receptors and pathways responsible for pair bonding in voles are also involved in cocaine addiction in rodents. This suggests a possible explanation for the addictive feeling of love.

This is your brain on Love

In humans, Donatella Marazziti, Professor of Psychiatry and Director of the laboratory of Psychopharmacology at the University of Pisa, has found that early stages of romance are linked with diminished levels of the neurotransmitter serotonin and of a serotonin receptor. These two molecules are also depleted in obsessive-compulsive disorder. Since both conditions (to different extents) also give rise to feelings of anxiety and obtrusive thinking, it is tempting to think of early love as a mild, temporary form of obsessive behavior. Early romance is also characterized by higher levels of several different molecules related to stress response. Twelve to 18 months into a relationship, both serotonin and the stress molecules are restored to normal levels.

Researchers like Helen Fisher of the Department of Anthropology at Rutgers University and Semir Zeki of UCL in London have done functional MRI studies to identify the regions of the brain that are activated or deactivated by romantic love. They've found that people in romantic love show increased activity in a number of different regions of the brain that are involved in the dopamine reward system. Parental love activates most of the same regions but not the hypothalamus, suggesting that the hypothalamus may be responsible for the sexual component of romantic love.

Areas that show reduced activity include the amygdala and the frontal and prefrontal cortecies. The amygdala is associated with fear and aversive learning, or learning from one's mistakes. The frontal and prefrontal cortecies are associated with the executive functions of analysis and judgment, delayed gratification, and predicting the outcomes of events. We can speculate that diminished activity in these regions explains why lovestruck persons do not seem to have full grasp of these particular functions. Fisher summarizes some of her findings magnificently in her 2008 TED talk.

The physiology of love is not totally understood, and research is ongoing. Researchers have begun to explain the pair bonding of animals such as voles, and have identified patterns of hormones and brain activity that show up among people in romantic relationships. What physiology tells us about love is what we knew all along—that it is a stressful matter bordering on an addiction or an obsessive disorder, that it muddles one's judgment and leads one to act rashly, and that as it grows, these disturbances fade and give way to calm and joy.

nextArticle.image_alt|e
iStock
arrow
Big Questions
What Makes a Cat's Tail Puff Up When It's Scared?
iStock
iStock

Cats wear their emotions on their tails, not their sleeves. They tap their fluffy rear appendages during relaxing naps, thrash them while tense, and hold them stiff and aloft when they’re feeling aggressive, among other behaviors. And in some scary situations (like, say, being surprised by a cucumber), a cat’s tail will actually expand, puffing up to nearly twice its volume as its owner hisses, arches its back, and flattens its ears. What does a super-sized tail signify, and how does it occur naturally without help from hairspray?

Cats with puffed tails are “basically trying to make themselves look as big as possible, and that’s because they detect a threat in the environment," Dr. Mikel Delgado, a certified cat behavior consultant who studied animal behavior and human-pet relationships as a PhD student at the University of California, Berkeley, tells Mental Floss. The “threat” in question can be as major as an approaching dog or as minor as an unexpected noise. Even if a cat isn't technically in any real danger, it's still biologically wired to spring to the offensive at a moment’s notice, as it's "not quite at the top of the food chain,” Delgado says. And a big tail is reflexive feline body language for “I’m big and scary, and you wouldn't want to mess with me,” she adds.

A cat’s tail puffs when muscles in its skin (where the hair base is) contract in response to hormone signals from the stress/fight or flight system, or sympathetic nervous system. Occasionally, the hairs on a cat’s back will also puff up along with the tail. That said, not all cats swell up when a startling situation strikes. “I’ve seen some cats that seem unflappable, and they never get poofed up,” Delgado says. “My cats get puffed up pretty easily.”

In addition to cats, other animals also experience piloerection, as this phenomenon is technically called. For example, “some birds puff up when they're encountering an enemy or a threat,” Delgado says. “I think it is a universal response among animals to try to get themselves out of a [potentially dangerous] situation. Really, the idea is that you don't have to fight because if you fight, you might lose an ear or you might get an injury that could be fatal. For most animals, they’re trying to figure out how to scare another animal off without actually going fisticuffs.” In other words, hiss softly, but carry a big tail.

nextArticle.image_alt|e
AFP, Getty Images
arrow
Big Questions
What Happened to the Physical Copy of the 'I Have a Dream' Speech?
AFP, Getty Images
AFP, Getty Images

On August 28, 1963, Martin Luther King Jr. stood on the steps of the Lincoln Memorial and gave a speech for the ages, delivering the oratorical masterpiece "I Have a Dream" to nearly 250,000 people.

When he was done, King stepped away from the podium, folded his speech, and found himself standing in front of George Raveling, a former Villanova basketball player who, along with his friend Warren Wilson, had been asked to provide extra security around Dr. King while he was speaking. "We were both tall, gangly guys," Raveling told TIME in 2003. "We didn't know what we were doing but we certainly made for a good appearance."

Moved by the speech, Raveling saw the folded papers in King’s hands and asked if he could have them. King gave the young volunteer the speech without hesitation, and that was that.

“At no time do I remember thinking, ‘Wow, we got this historic document,’” Raveling told Sports Illustrated in 2015. Not realizing he was holding what would become an important piece of history in his hands, Raveling went home and stuck the three sheets of paper into a Harry Truman biography for safekeeping. They sat there for nearly two decades while Raveling developed an impressive career coaching NCAA men’s basketball.

In 1984, he had recently taken over as the head coach at the University of Iowa and was chatting with Bob Denney of the Cedar Rapids Gazette when Denney brought up the March on Washington. That's when Raveling dropped the bomb: “You know, I’ve got a copy of that speech," he said, and dug it out of the Truman book. After writing an article about Raveling's connection, the reporter had the speech professionally framed for the coach.

Though he displayed the framed speech in his house for a few years, Raveling began to realize the value of the piece and moved it to a bank vault in Los Angeles. Though he has received offers for King’s speech—one collector wanted to purchase the speech for $3 million in 2014—Raveling has turned them all down. He has been in talks with various museums and universities and hopes to put the speech on display in the future, but for now, he cherishes having it in his possession.

“That to me is something I’ll always be able to look back and say I was there,” Raveling said in the original Cedar Rapids Gazette article. “And not only out there in that arena of people, but to be within touching distance of him. That’s like when you’re 80 or 90 years old you can look back and say ‘I was in touching distance of Abraham Lincoln when he made the Gettysburg Address.’"

“I have no idea why I even asked him for the speech,” Raveling, now CEO of Coaching for Success, has said. “But I’m sure glad that I did.”

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios