Emilio Ferrer, a psychology professor at University of California, Davis, who has conducted a series of studies on couples in romantic relationships, finds that couples connected to monitors measuring heart rates and respiration get their heart rate in sync, and they breathe in and out at the same intervals.

To collect the data, the researchers conducted a series of exercises, sitting 32 heterosexual couples a few feet away from each other in a quiet, calm room. The couples did not speak or touch.

“We’ve seen a lot of research that one person in a relationship can experience what the other person is experiencing emotionally, but this study shows they also share experiences at a physiological level,” Ferrer says.

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