"Vagus nerve      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.             via The Atlantic - No such thing as unconditional love"
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