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What Happens to Your Brain When You Fall in Love?

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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.

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What Happens When You Flush an Airplane Toilet?
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For millions of people, summer means an opportunity to hop on a plane and experience new and exciting sights, cultures, and food. It also means getting packed into a giant commercial aircraft and then wondering if you can make it to your next layover without submitting to the anxiety of using the onboard bathroom.

Roughly the size of an apartment pantry, these narrow facilities barely accommodate your outstretched knees; turbulence can make expelling waste a harrowing nightmare. Once you’ve successfully managed to complete the task and flush, what happens next?

Unlike our home toilets, planes can’t rely on water tanks to create passive suction to draw waste from the bowl. In addition to the expense of hauling hundreds of gallons of water, it’s impractical to leave standing water in an environment that shakes its contents like a snow globe. Originally, planes used an electronic pump system that moved waste along with a deodorizing liquid called Anotec. That method worked, but carrying the Anotec was undesirable for the same reasons as storing water: It raised fuel costs and added weight to the aircraft that could have been allocated for passengers. (Not surprisingly, airlines prefer to transport paying customers over blobs of poop.)

Beginning in the 1980s, planes used a pneumatic vacuum to suck liquids and solids down and away from the fixture. Once you hit the flush button, a valve at the bottom of the toilet opens, allowing the vacuum to siphon the contents out. (A nonstick coating similar to Teflon reduces the odds of any residue.) It travels to a storage tank near the back of the plane at high speeds, ready for ground crews to drain it once the airplane lands. The tank is then flushed out using a disinfectant.

If you’re also curious about timing your bathroom visit to avoid people waiting in line while you void, flight attendants say the best time to go is right after the captain turns off the seat belt sign and before drink service begins.

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Why is Friday the 13th Considered Unlucky?
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Today, people around the globe will feel uneasy about getting out of bed, leaving their homes, or going about their normal daily routines, all because of a superstition. These unfortunate folks suffer from paraskavedekatriaphobia, a common neurosis familiar to us all: the fear of Friday the 13th. But just where did this superstitious association come from, and how did it catch on?

The truth is that no one is absolutely sure where the idea that Friday the 13th is unlucky originated. Donald Dossey, the founder of the Stress Management Center and Phobia Institute in Asheville, North Carolina, suspects the fear can be traced back to a Norse myth about 12 gods who had a dinner at Valhalla—the fabled hall where legendary Norse heroes feasted for eternity after they died—that was interrupted by a 13th guest, the evil and mischievous god Loki.

According to legend, Loki tricked Höðr (the blind god of winter and son of Odin, the supreme god in Norse mythology) into shooting his brother Baldr (the benevolent god of summer who was also a son of Odin) with a magical spear tipped with mistletoe—the only substance that could defeat him. Thus the number 13 was branded as unlucky because of the ominous period of mourning following the loss of such powerful gods by this unwanted 13th guest.

For whatever reason, among many cultures, the number 12 emerged throughout history as a "complete" number: There are 12 months in a year, 12 signs of the zodiac, 12 Gods of Olympus, 12 sons of Odin, 12 labors of Hercules, 12 Jyotirlingas or Hindu shrines where Shiva is worshipped, 12 successors of Muhammad in Shia Islam, and 12 tribes of Israel. In Christianity, Jesus was betrayed by one of his 12 Apostles—Judas—who was the 13th guest to arrive for the Last Supper. Surpassing the number 12 ostensibly unbalances the ideal nature of things; because it is seen as irregular and disrespectful of a sense of perfection, the number 13 bears the stigma of misfortune and bad luck we know today.

WHY FRIDAY?

Friday joins in the mix mostly because all of the early accounts of Jesus’s crucifixion agree that it took place on Friday—the standard day for crucifixions in Rome. As Chaucer noted in The Canterbury Tales, "And on a Friday fell all this mischance." Yet perpetuating Friday as an unlucky day in America came from the late 19th-century American tradition of holding all executions on Fridays; Friday the 13th became the unluckiest of days simply because it combined two distinct superstitions into one. According to the Oxford University Press Dictionary of Superstitions, the first reference to Friday the 13th itself wasn’t until 1913. (So despite actually occurring on Friday, October 13, 1307, the popular notion that the Friday the 13th stigma comes from the date on which the famed order of the Knights Templar were wiped out by King Philip of France is just a coincidence.)

The repercussions of these phobias reverberated through American culture, particularly in the 20th century. Most skyscrapers and hotels lack a 13th floor, which specifically comes from the tendency in the early 1900s for buildings in New York City to omit the unlucky number (though the Empire State Building has a 13th floor). Some street addresses also skip from 12 to 14, while airports may skip the 13th gate. Allegedly, the popular Friday the 13th films were so-named just to cash in on this menacing date recognition, not because the filmmakers actually believed the date to be unlucky.

So, is Friday the 13th actually unlucky? Despite centuries of superstitious behavior, it largely seems like psychological mumbo jumbo. One 1993 study seemed to reveal that, statistically speaking, Friday the 13th is unlucky, but the study's authors told LiveScience that though the data was accurate, "the paper was just a bit of fun and not to be taken seriously." Other studies have shown no correlation between things like increased accidents or injuries and Friday the 13th.

And Friday the 13th isn't a big deal in other cultures, which have their own unlucky days: Greeks and Spanish-speaking countries consider Tuesday the 13th to be the unluckiest day, while Italians steer clear of Friday the 17th. So today, try to rest a little easy—Friday the 13th may not be so unlucky after all.

Additional Source: 13: The Story of the World’s Most Popular Superstition.

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