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The Science of Love Letters

February 10, 2012

In 1779 Benjamin Franklin, when serving as the U.S. envoy to France, fell in love with Anne Catherine Helvétius, the widow of the Swiss-French philosopher, Claude-Adrien Helvétius. In an attempt to win her affections, Franklin sent her many letters expressing his love, admiration, and passion for her. In one he claimed that in a dream he was transported to the Elysian Fields, where he discovered that his late wife and Madam Helvétius’s late husband had married one another. It would, he suggested, only be fair if they avenged this union by themselves marrying. In another, more passionate plea, he wrote “If that Lady likes to pass her Days with him, he in turn would like to pass his Nights with her; and as he has already given her many of his days…she appears ungrateful never to have given him a single one of her nights.”

The lover’s mind, as Alfred Lord Tennyson explained, “lightly turns to thoughts of love” with the arrival of Spring and its harbinger: St. Valentine’s Day. But this holiday brings a responsibility: the crafting of a “written missive that defines and describes the current and/or desired nature of an amative relationship between the sender and recipient”–in other words, a love letter. This burden is lightened, to some degree, by the availability of pre-built greeting cards, red roses, candy hearts, and the Love You! app for your smart phone, but the traditional love letter makes it possible to convey one’s love for another in a more coherent and influential way (and, as Marcus Cicero pointed out, “a letter does not blush”).

But what should you say in your love letter to your Valentine? Should lovers craft sentimental love poems, confess their undying commitment in flowery prose, or pen flirtatious notes that hint at the sexual pleasures found in each other’s arms? Did Ben Franklin’s sly request for a night together endear him to the widow, or would a letter like Kahlil Gibran’s to Mary Haskill be more likely to curry favor in the recipient’s heart: “You are like the Great Spirit, who befriends man not only to share his life, but to add to it. My knowing you is the greatest thing in my days and nights, a miracle quite outside the natural order of things.”

Fortunately, theory and research offer some suggestions to the love-besotted crafter of persuasive prose. Yale psychologist Robert Sternberg’s theory of love, for example, suggests that the ideal love letter should include content relevant to love’s three basic components—intimacy, passion, and commitment.

The three-factor theory of consumate love (Sternberg).

Intimacy is the emotional component: the “close, connected, and bonded” feelings lovers experience. Passion is the motivational component. Like passionate love, it includes physical attraction, sexual desire, sexuality. Sternberg’s third component, decision/commitment, speaks of one’s hope that the relationship will be long-lasting. Words like loyalty, responsibility, faithfulness, and devotion characterize commitment. The consummate love letter would, in theory, combine all three elements.

To test Sternberg’s theory Kelli Taylor and I developed a dozen different love letters and asked men and women to read and evaluate each one’s success in expressing love. Some of the letters were filled with expressions of tender intimacy: “You are my best friend,” “I can share any secret with you,” and “I feel so close and connected to you.” Others confessed ardor and passion: “You are a wonderful lover,” and “Our nights are pure, physical pleasure.” Still others spoke of commitment—a desire for a long-term relationship—or a worry about what the future might bring. And some letters included two of these elements, and one—the super-love-letter—combined all three.

We discovered that, when it comes to love letters, commitment conquered all. The letter that proclaimed “I know we will be happy together for the rest of our lives” and “I couldn’t imagine a world without you in it” was rated much higher, in terms of expressing love, than one that made no mention of commitment or, even worse, explained: “I am really happy being with you, but who knows what’s going to happen.” Adding language that spoke of closeness and caring increased the letter’s good impression with readers, but it was commitment that left readers feeling loved and in love. One woman said “I think he is really comfortable and at ease with me, it gives me a sense of being absolutely secure and comfortable.” A 20-year old man explained “This woman is in love with me and shows total commitment and loyalty to me.”

And what about expressing passion in a letter? Frisky letters, which went on for too long about the sender’s sexual passions, were viewed negatively; they seemed like lust letters instead of love letters. One 20 year-old woman concluded the “relationship appears to be purely physical, with no sentiments or emotional commitment.” Another complained “I don’t want my love letter talking about how crazy sex makes my partner feel.” But what about men? Did they prefer a letter with sensual details to one that spoke of closeness and commitment? No. Men were not as embarrassed by the provocative letters as were women, but they too gave them low ratings.

We also discovered that a message of commitment need not be delivered in a traditional love letter or a card: email will do. In a second study volunteers were told that at some point in the next week they would be receiving a love letter by email. All they needed to do was read it and imagine how they would react if they got such an email from someone they were dating. Once again, it was the message that spoke of the relationship, a future together, and years of happiness ahead that turned the email into a love email.

Unexpectedly, the super-love-letter that combined all three of the Sternberg model was not judged as uniquely loving. In the language of statistics, rather than love, we obtained only main effects, without a hint of an interaction.

To summarize our findings in the language of candy conversation hearts, all the letters said, at some point, “I love you,” but the strongest letters added “Be mine forever” and “Best friends.” The “Hot lover” letter was more likely to backfire than win a heart.

This research, in its small way, is a reminder of the value of the scientific study of interpersonal relationships. There are those who consider the study of liking and love to be a frivolous pursuit. For example, some years back Senator William Proxmire of Wisconsin discovered that the National Science Foundation was funding studies of attraction and love. Outraged by what he felt was useless research, Proxmire insisted that “Americans want to leave some things in life a mystery, and right at the top of the things we don’t want to know about is why a man falls in love with a woman and vice versa.” But the study of relationships yields the knowledge needed to strengthen those relationships and enrich people’s lives. People, when asked about sources of lasting happiness and satisfaction, put their relationships with others at the top the list, far higher in importance than career accomplishments, financial security, and material possessions. Health and well-being are linked to physical factors, but also to the quality and reliability of one’s relationships with others (Reis, 2011). Researchers, by studying relationships, find solutions to many of the most basic problems people face as individuals and as a species: divorce, violence, prejudice, conflict, and loneliness. Certainly many questions are worth studying scientifically–it would be good to know, for example, more about the moons around Saturn, the penguin’s top swimming speed, or DNA of the drosophilae–but is there really anything more important than understanding the whys and wherefores of our relationships with others?


Reis, H. T. (2011). “It’s Not a Matter of Life and Death.” Personality and Social Psychology Connections. Retrieved from

5 Comments leave one →
  1. February 10, 2012 11:11 pm

    This really makes me want to write a super love letter. But how can I fit it in a tweet?

    It’s amazing really how writing makes such a difference in our lives. I encourage everyone to do more of it. It’s good for you, and for others.


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