

This graph shows something quite wonderful. It shows that in a couple, the heart rates of a man and woman are in sync. Yes, when you're involved in a romantic relationship, your heart beats as fast as your partner's.

This couple was one of the 32 heterosexual couples in a study conducted by physiologies at UC Davis in the US that aimed to see if people in romantic relationships co-regulated their physiologies with their partners. By co-regulated, read change; by physiologies, read heart rates.



In one of the experiments, the couples sat facing each other but just far enough that they would not be able to touch. The researchers asked them to simply stare at one another for three minutes straight in as calm a manner as possible (ahem) while they monitored the couple's heart rates.



The graph above does not actually show the heart rates of the man and woman changing with time. Instead it shows a complex measure of heart rate which takes into consideration the observed changes in heart rate due to the individual self-regulating, that is trying to control himself or herself by keeping calm for instance, as well as the changes associated with the individual as he or she unconsciously mimics the partner, known as co-regulation. Since the extent of both self-regulation and co-regulation is different in man and woman, this measure allows for comparison between the two. In the above graph, the measure is actually shown by a blue line.



But the blue line is so closely matched by a red line that you barely see it. What does the red line indicate? It indicates the changes one would expect to see if the couple's heart rates are the same. Therefore the more closely the blue and red lines match, the closer an individual's heart rate is to the partner's. It is no surprise then that when the researchers compared the measure of heart rates between people not involved in a romantic relationship, the blue and red lines did not match.



The researchers also found that it was the women who tended to adjust their heart rates to their partners. Why this actually happens on a psychological level however is still a mystery. The researchers speculate that women have a strong link to their partners may have something to do with them having more empathy.



The study does have some limitations, which the researchers readily acknowledge. For instance, the study only looked at 32 couples which is a small sample. It also only looked at heterosexual couples. But regardless, it does at least give some evidence that we match our physiologies without even knowing to that special someone's.



And inspired from this study, here's a great line which may do wonders today of all days: "I love you so much that my heart beats as fast as yours whenever I see you." Not ravishingly special at first sight but just explain the science and we'll talk again later.



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Reference: Ferrer, E. & Helm, J.L. (2012) Dynamical systems modeling of physiological coregulation in dyadic interactions. International Journal of Psychophysiology. DOI: 10.1016/j.ijpsycho.2012.10.013.