What is love? (Baby don't hurt me)
"Do you believe in love at first sight, or should I walk by again?" - Unknown When I sit at my local coffee shop to work on planning experiments, about 15-20% (rough estimation) of the patrons around me appear to be on dates. Fresh off the heels of Valentine's Day, a thought passed through my head that I thought was pretty intriguing - what is love?
Figure 1: Wall-E and EVE. This post may not apply to robots.
Emotion is a classic topic in science that has been somewhat difficult to explain over the centuries. As a biologist, my first instinct is to boil down such a complex social phenomenon into its individual physiological components. The difference between happiness, sadness, jealousy, anger, and everything in between is simply the way in which the electrical signals in your brain coordinate the release of neurotransmitters, like dopamine and GABA. Some see this perspective as rather dull, but I think it's really quite beautiful!
When you see someone very attractive, what happens to you? Your heart begins to race, you start to feel very warm, and it seems like everything surrounding the object of your affection fades into the background. What explains this fixation? A fascinating review in the Journal of Sexual Medicine focused on this specific topic. With the use of advanced technologies, we can better visualize the physiological basis behind that warm and fuzzy feeling you get when you see someone you're interested in!
Ortigue et al. differentiate between two types of love in the review I've hyperlinked above. The first is known as passionate love, which is the sort of love you have towards a significant other. The second is compassionate love, which is the love you might feel towards a good friend or a family member. By using a device known as functional magnetic resonance imaging (fMRI), scientists can see how blood flow throughout the brain changes when these types of love are experienced.
In one study, scientists allowed participants to view images of their respective partners for about 17 seconds, while taking a peak into their brain via fMRI. They found that blood flow was significantly increased in areas of the brain associated with reward and euphoria, including areas of the brain that are also associated with euphoria-inducing drugs like cocaine. Activity was also shown in areas involved in memory. Simultaneously, blood flow was decreased in areas of the brain associated with anxiety and fear, such as the amygdala. These are also the areas of the brain that are highly active in humans who experience emotional stress, like a bad break up. A second study found that the reward centers of the brain are also stimulated when participants were shown the name of their significant other. How romantic!
Bartels and Zeki in 2004 performed a similar study, but this time they were seeking to further understand compassionate love. The experimental design was similar to the one above. In this case, the participants were all mothers who were shown pictures of their children. The researchers found significant activity in an area of the brain known as the periaqueductal gray matter (PAG), an area of the brain that is involved in pain suppression during intense emotional experiences, such as childbirth. Activity was also shown in areas of the brain associated with higher cognitive processing.
The same author has also discussed the idea of "love at first sight", which about 58% of Americans believe is a real phenomenon. As it turns out, when you look at someone who you find extremely attractive, 12 different areas of the brain work together to release a whole host of different neurotransmitters within 0.2 seconds of visual contact. Just think about that - within a fifth of a second, your brain is able to tell you "Wow, this person is incredible!" as opposed to the person to their left or right. Whether or not this feeling of intense emotion is actually "love" is a debate that continues to rage on today. What does this scientist think it means? From a biological perspective, it goes something like this:
"Ah, this person looks like they have good genes. Probably would make strong, healthy offspring. Proceed with mating."
In short, your brain is capable of generating very different feelings of love depending on the situation. It's a pretty incredible system, isn't it? Of course, why some people trigger strong feelings of love over others is a lengthy subject and probably too much for the scope of this blog. So when the next time you see your significant other (or that cute barista working the espresso machine), think about how hard your brain is working to say, "Hey buddy, time to make your move!"