Heart rates synchronise if two people get on well during first date

When people feel instant chemistry with each other on a first date, their hearts start to beat in tune, a new study shows.

We often think we know what we are looking for in a partner, but research shows that the people we actually end up falling for often don’t match our ideal preferences.

“While someone may seem a perfect match on Tinder, we may feel nothing when we meet the person in real life,” says Eliska Prochazkova at Leiden University in the Netherlands. This may be because attraction isn’t simply based on what someone “looks like on paper”, but also on a gut feeling we get when we are with them, she says.

To study what happens at a physiological level when people instantly spark on a first date, Prochazkova and her colleagues set up “dating cabins” at three festivals – one for music, one for arts and one for science – in the Netherlands.

They invited 142 single heterosexual males and females aged 18 to 38 to go on 4-minute blind dates in these cabins. The participants wore eye-tracking glasses, heart rate monitors and devices for monitoring the sweatiness of their palms.

Some pairs reported becoming more attracted to each other as their dates progressed, while others failed to click. Of all the pairs that were matched up, 17 per cent expressed a mutual wish to go on another date.

The pairs that wanted to see each other again and rated each other as attractive tended to be those who developed physiological synchrony. Their heart rates began to speed up and slow down at the same time and their palm sweatiness increased and decreased in tandem.

It was common for pairs to also mirror each other’s smiles, laughs, head nods and hand gestures, but this type of synchrony didn’t predict mutual attraction.

The results largely replicate those that the team found in an earlier version of the study, which they posted to a preprint server in 2019.

The mechanism underlying physiological synchrony is still unclear, but it is possible that when you meet someone you really like, you unconsciously pay attention to their micro-expressions, such as pupil dilation, eye blinking or blushing, says Prochazkova. “Although you do not consciously register these subtle changes, your brain and body unconsciously process these micro-expressions, which causes your heart rate and skin conductance to sync with the partner.”

Physiological synchrony has also been observed between mothers and their babies while they are playing together, suggesting it may help to strengthen social bonds more generally, says Prochazkova.

Although the new study shows what happens at a deeper biological level when two people feel mutual attraction, we still need more research to answer why we fall for the people we do, says Prochazkova. “What sparks this feeling between people remains one of the unsolved mysteries of science.”