Who put the heart in Valentine’s Day?

Every year on Valentine’s Day, couples exchange romantic gifts of chocolates and roses and jewelry. Some will take vacations. Some will pledge their love. According to the National Retail Federation, last year Americans spent $18.6 billion to show their affection.

But, to paraphrase Tina Turner, “What’s the heart got to do, got to do with it?”

“Love is really a function of the brain, not the heart,” said OMRF President Stephen Prescott, M.D. “In 2004, anthropologist Helen Fisher published research of brain scans to show that the feelings we associate with love are caused by a chemical reaction.”

So that blissful feeling of love is really a mélange of norepinephrine, dopamine and other chemicals.

But where does the heart come in? Rodger McEver, Ph.D., chair of OMRF’s Cardiovascular Biology Research Program, said his scientists spend their time looking at how hearts (and blood vessels and lymph nodes) work in keeping people alive—not its role in love.

Scientist and philosopher Aristotle believed the heart was the source of all passions. The first known appearance of the heart symbol was in the manuscript of the French “Roman de la poire”—though this heart was upside down and pointed by a lover at his lady.

And one origin of the familiar heart shape comes from a French nun, Saint Margaret Mary Alacoque, who had visions of “The Sacred Heart” of Jesus in the 1600s. That heart, surrounded by flames, is more anatomically accurate than the symbol bandied about today, thanks to what looks like an aorta and pulmonary artery feeding into the top.

Does the connection between the heart and love have something to do with how fast that muscle beats when you’re in the presence of someone you love? Maybe, said Prescott, a trained cardiologist. But the precise lineage might be lost to the ages.

But that hasn’t stopped the heart becoming a big part of modern society. In 1977, the heart logograph was officially used to replace the word “love” to promote tourism in the “I ♥ NY” campaign. In more recent years, video games used the heart symbol to show the vitality of characters and restaurants began to mark healthy dishes with it.

“All this heart talk does remind me of a story, though,” Prescott said. “Years ago, while on a trip to Mexico, I skipped a day—and then a whole week—of bird watching and spent my time painting a custom Valentine’s card for my wife, Susan.

“But, of course, I painted a realistic heart. How romantic is that?”