Getting the vole story

The prairie vole is one species among the only 3% of mammals that live monogamously.

Boys, Valentine’s Day is coming up. According to a U.S. census, 53% of women would dump their boyfriend if he didn’t get her anything for Valentine’s Day. It’s the time to buy flowers, heart-shaped necklaces, and chocolates, watch chick-flicks, go out for expensive dinners, and even propose.


Valentine’s Day is not when people like to hear that love may not be a mystical, cosmic force, but more of a scientifically explained soup of brain chemicals and evolution.


But here it is anyway, through the eyes of a rodent.


It’s now almost common knowledge, what the average man or woman subconsciously looks for when choosing the perfect mate. Men look for women with voluptuous hips, smooth skin, and glossy hair. Women look for men with broad shoulders, a deep voice, and a good income.


But what makes us fall in love?


Scientists decided to look into one species among the only 3% of mammals that form monogamous relationships: the prairie vole. The prairie vole is a rodent, resembling a fat mouse, that forms a lifelong relationship with its partner after they mate. The male avoids “cheating” on his partner, jealously defends her against other males, and loyally helps bring up their offspring.


Scientists decided to look into the chemical events occurring in the voles’ brains to see what could trigger such strong bonds. They found that voles’ brains had a particularly interesting distribution of the hormones oxytocin, vasopressin, and dopamine.


During sex, the voles’ brains shoot out vasopressin, oxytocin, and dopamine. Brain receptors designed to collect these hormones are located in the “rewards and reinforcements” area of the brain. When the voles mate, they get “rewarded” with a good feeling. They end up associating that good feeling with their mate, and from then on only prefer spending time feeding, mating, and raising offspring with each other.


Humans, on the other hand, have more complex brains, so scientists can’t rely on injecting us with hormones to help us form longer relationships.


But they are trying.


Scientists already found that humans also get surges of vasopressin and oxytocin during sex. They believe that humans may have defects in similar areas of their brains to voles when members of either species fail to form good relationships. If scientists can tap into where or what is causing the inability to form relationships, including ordinary friendships or business relationships with colleagues at work, they might be able to produce a drug to fix it.


At University College in London, scientists Andreas Bartels and Semir Zeki collected students claiming to be madly in love. They set up a brain scanner, looked for patterns in brain activity, and analyzed the parts of their brains that were stimulated by love.


They found that the area where love supposedly manifests is tinier than that activated for simple friendships. However, the area coincided with that which is sensitive to feelings in the gut and that which creates euphoria. These euphoric areas are the same areas stimulated when a person takes cocaine.


According to Bartels and Zeki, it’s quite possible for humans to become love “addicts”. The attachment to the sensation of deep love is not a far cry from taking coke!


Question: if humans can indeed form strong, lifelong bonds like prairie voles, then why do people cheat?


One Las Vegas social media company,, released some interesting statistics last Thursday. The website found that 65% of people cheating on Valentine’s Day are women. How did the website find out? Did the cheating women suddenly become overwhelmed with guilt and admit it online? Nope. Other women outed them.


Cheating behaviour is characteristic of a vole species otherwise similar to the prairie vole, namely the montane vole. Montane voles mate almost oppositely to prairie voles. Montane voles prefer one-night stands, almost never committing to only one other vole of the opposite sex, and caring little for his offspring. They do not form lifelong relationships with a mate.


Scientists decided to take oxytocin and inject it into the montane voles in an attempt to induce “love”, or at least a long-term relationship. After injection, the montane vole did not even respond to the hormone. However, when it was injected into a prairie vole, the vole locked onto a potential mate even when scientists kept the two from mating. The prairie vole preferred only that mate, even when other voles courted it.


The difference lies in the receptors present in the prairie vole brain. These receptors do not exist in the montane vole. The montane vole could not be induced to be faithful.


Humans are classed as “(generally) monogamous”, although there is ample evidence to the contrary. There are many reasons why people cheat. One major idea may be that people desire the extreme, euphoric emotions of that first stage of love. Whether we like to hear it or not, that great feeling usually doesn’t last forever, even when a more mature, perhaps “truer” love outlasts it.


It doesn’t take a scientist to see that a loving relationship evolves in stages over a long time. When first falling in love, you feel a high and become obsessed with that one person, thinking and dreaming about them, longing to be with them every waking moment. This is when intimacy is greatest.


Over the years, as you get on with life, you sober up, but the bonds deepen. Sometimes children enter the picture, and then you spend more time raising the kids and less time with each other.


This too can contribute to a deeper, more “companionate” love, in which you simply like each other’s company. You like chatting over the newspaper or playing board games on a rainy day. This type of love has less passion.


Less passion may not be a bad thing.


Long-lasting relationships, even from an evolutionary perspective, are critical to ensure that children are raised successfully. Desirous passion at this stage of life would distract from family, career, and life in general.


This isn’t to imply that there are no couples out there who have lived together for decades without romantic passion. But scientists claim these couples are rare. If love fizzles and cools, it may be meant to. There may be less romantic excitement, but the bond between the couple could be stronger than ever, and their children happier.