The Symbol of Love

Valentine’s Day is approaching, and love is in the air. Everywhere you look, there are heart-shaped cards, candies, and decorations. But February isn’t the only time you’ll see this famous shape. Heart icons appear year-round in advertisements, on clothing, and as emojis in texts. Pop stars even make the shape with their hands to express gratitude to fans at concerts. Across the globe, the heart is a universal symbol of love.

Valentine’s Day is near, and love is in the air. Heart-shaped cards, candies, and decorations are everywhere. But you won’t see this famous shape only in February. Heart icons appear all year in ads, on clothing, and as emojis in texts. Pop stars even make the shape with their hands to thank fans at concerts. Around the world, the heart is a common symbol of love.

Some modern ideas about the heart stem from the beliefs of ancient Greek scientists, known as philosophers. They came up with theories about how the human body worked—many of which turned out to be incorrect. “Ancient Greek philosophers believed that the human body was controlled by four humors, or fluids: black bile, yellow bile, phlegm, and blood,” explains Brad Bouley. He’s a professor of scientific and religious history at the University of California, Santa Barbara.

To the ancient Greeks, a healthy person was someone who had all their humors in balance. They believed that too much or too little of any of these fluids caused physical, emotional, or psychological problems. Too much yellow bile was thought to make a person angry, while too much black bile made them depressed. Blood was the humor associated with love and passion. “The heart was seen as a motor that heated fresh blood and moved it through the body, so it was also viewed as the origin of passionate feelings,” Bouley explains.

Some modern ideas about the heart come from ancient Greek scientists, known as philosophers. They came up with theories about how the human body worked. Many of those theories turned out to be incorrect. “Ancient Greek philosophers believed that the human body was controlled by four humors, or fluids: black bile, yellow bile, phlegm, and blood,” explains Brad Bouley. He’s a professor of scientific and religious history at the University of California, Santa Barbara.

To the ancient Greeks, a healthy person had all their humors in balance. They believed that too much or too little of any of these fluids caused problems. These problems could be physical, emotional, or psychological. Too much yellow bile was thought to make a person angry. Too much black bile made them depressed. Blood was the humor linked to love and passion. “The heart was seen as a motor that heated fresh blood and moved it through the body, so it was also viewed as the origin of passionate feelings,” Bouley explains.

The scalloped shape of the modern heart icon may trace back to early scientific ideas about the body. “Ancient medical texts didn’t contain pictures, but Greek and Roman philosophers describe the heart as having two chambers [hollow spaces] and an indent in it,” says Bouley. “If you were to try to draw an organ based on that description, you can see how it might translate to the heart shape we see today.”

The modern heart icon has curves with an indent. This shape may go back to early scientific ideas about the body. “Ancient medical texts didn’t contain pictures, but Greek and Roman philosophers describe the heart as having two chambers [hollow spaces] and an indent in it,” says Bouley. “If you were to try to draw an organ based on that description, you can see how it might translate to the heart shape we see today.”

Although the heart may not control our feelings, our feelings can have major effects on our heart. When you feel joy, like when you’re in love, your brain releases oxytocin and dopamine. These chemicals increase feelings of happiness and well-being. They also cause heart rate to increase and arteries to dilate, or enlarge. “This increases blood flow throughout the body, providing organs with more oxygen and improving their function,” says Dr. Ilan Wittstein. He’s a cardiologist, or heart doctor, at Johns Hopkins University in Maryland. “People who experience more positive emotions seem to have fewer heart problems in the long term,” he explains.

The heart may not control our feelings. But our feelings can have major effects on our heart. Take what happens when you feel joy, like when you’re in love. Your brain releases oxytocin and dopamine. These chemicals increase feelings of happiness and well-being. They also increase heart rate and cause arteries to dilate, or enlarge. “This increases blood flow throughout the body, providing organs with more oxygen and improving their function,” says Dr. Ilan Wittstein. He’s a cardiologist, or heart doctor, at Johns Hopkins University in Maryland. “People who experience more positive emotions seem to have fewer heart problems in the long term,” he explains.

The connection between our brains and our hearts is complex, and scientists still aren’t sure exactly how the two interact. “Our scientific understanding of how our bodies and feelings are related is still quite basic,” says Wittstein. Everyone experiences emotions differently, making them difficult to measure. After all, how can anyone scientifically define a feeling as mysterious and complicated as love?

The connection between our brains and our hearts is difficult to explain. Scientists still aren’t sure exactly how the two affect one another. “Our scientific understanding of how our bodies and feelings are related is still quite basic,” says Wittstein. Everyone experiences emotions differently. That makes emotions hard to measure. After all, a feeling like love is mysterious and complicated. How can anyone define it scientifically?