Using dating applications and websites are among the most popular online activities in the world. But many online introductions fizzle out, or if the two meet, it isn’t followed up by a repeat performance. People who are seeking a romantic relationship know how important that first date can be.  

Many would-be marriage partners wonder when falling in love what makes us attracted to some people and not to others? The answer will be surprising to most of us – but it wasn’t to the team of researchers led by Dr. Shir Atzil of the psychology department at the Hebrew University in Jerusalem (HUJI). “Connecting with a partner depends on how well we can synchronize our bodies. We specialize in studying parent-infant bonding – and we had already seen the same thing there,” she explained.   

Classic evolutionary theories of mate selection emphasize immediate and static features such as physical appearance and fertility. However, they do not explain how initial attraction temporally unfolds during an interaction nor account for mutual physiological or behavioral adaptations that take place when two people become attracted.

“Humans belong to a limited number of mammalian species who form long-lasting pair bonds with selected sexual partners Unlike parental bonding, pair-bonding is an attachment between two adults that includes a voluntary selection of the partner. Pair bonding in humans is characterized by sexual desire and romantic infatuation, followed by a long-lasting attachment and familial cooperation,” they wrote. “Selecting a romantic partner is a significant process in human life, affecting many aspects of living and well-being. Yet, little is known about the bio-behavioral mechanisms underlying this selection in humans.”

The researchers looked at how a heterosexual couple’s physiology and behavior adapt to each other during that first encounter.  The study was based on a speed-date experiment with university undergraduates that consisted of 46 dates. Each lasted just five minutes during which the levels of physiological regulation of each partner were recorded with a band worn on the wrist. 

Behavioral movements, such as nodding, moving an arm and shifting a leg were also recorded in each partner during the date. After the encounter, the couple assessed the romantic interest and sexual attraction they felt for each other.  The study clearly showed that when couples synchronize their physiology with one another and adapt their behavioral movements to their partner during the date, they are romantically attracted to one another.  This research was recently published in Nature Pubications’ prestigious journal Scientific Reports under the title “Bio-behavioral synchrony is a potential mechanism for mate selection in humans.”

Interestingly, the study also showed that the degree of synchrony affected men and women differently. Although for both genders synchrony predicted attraction, women were more sexually attracted to men who showed a high level of synchrony – “super-synchronizers” who were viewed by women as highly desirable.

Our research,” said Atzil, “shows that behavioral and physiological synchrony can be a useful mechanism to attract a romantic partner. However, we still don’t know whether synchrony raises attraction or does the feeling of attraction generate the motivation to synchronize?”  This is an area of research that Atzil is planning to investigate.