The vagus nerve's potential for love can actually be measured by examining a person's heart rate in association with his breathing rate, what's called "vagal tone." Having a high vagal tone is good: People who have a high "vagal tone" can regulate their biological processes like their glucose levels better; they have more control over their emotions, behavior, and attention; they are socially adept and can kindle more positive connections with others; and, most importantly, they are more loving. In research from her lab, Fredrickson found that people with high vagal tone report more experiences of love in their days than those with a lower vagal tone.
Historically, vagal tone was considered stable from person to person. You either had a high one or you didn't; you either had a high potential for love or you didn't. Fredrickson's recent research has debunked that notion.
In a 2010 study from her lab, Fredrickson randomly assigned half of her participants to a "love" condition and half to a control condition. In the love condition, participants devoted about one hour of their weeks for several months to the ancient Buddhist practice of loving-kindness meditation. In loving-kindness meditation, you sit in silence for a period of time and cultivate feelings of tenderness, warmth, and compassion for another person by repeating a series of phrases to yourself wishing them love, peace, strength, and general well-being. Ultimately, the practice helps people step outside of themselves and become more aware of other people and their needs, desires, and struggles—something that can be difficult to do in our hyper individualistic culture.
Fredrickson measured the participants' vagal tone before and after the intervention. The results were so powerful that she was invited to present them before the Dalai Lama himself in 2010. Fredrickson and her team found that, contrary to the conventional wisdom, people could significantly increase their vagal tone by self-generating love through loving-kindness meditation. Since vagal tone mediates social connections and bonds, people whose vagal tones increased were suddenly capable of experiencing more micro-moments of love in their days. Beyond that, their growing capacity to love more will translate into health benefits given that high vagal tone is associated with lowered risk of inflammation, cardiovascular disease, diabetes, and stroke.
Fredrickson likes to call love a nutrient. If you are getting enough of the nutrient, then the health benefits of love can dramatically alter your biochemistry in ways that perpetuate more micro-moments of love in your life, and which ultimately contribute to your health, well-being, and longevity.
Fredrickson's ideas about love are not exactly the stuff of romantic comedies. Describing love as a "micro-moment of positivity resonance" seems like a buzz-kill. But if love now seems less glamorous and mysterious then you thought it was, then good. Part of Fredrickson's project is to lower cultural expectations about love—expectations that are so misguidedly high today that they have inflated love into something that it isn't, and into something that no sane person could actually experience.