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If you want someone to like you, forget about body language – the real measure of whether two people hit it off is how much they synchronise internal bodily functions, like heart rate and sweating.

People on a mock blind date liked each other more if they had simultaneous surges in their heart rate and skin conductivity. “You hear about people who are well suited to each other in theory but there is no spark – we wanted to know if you can quantify the spark,” Mariska Kret of Leiden University in The Netherlands said at the European Federation of Primatology meeting in Oxford last week.

Kret’s team investigated by setting up a cabin at a music festival, where people could take part in short one-to-one meetings with potential partners. They were allowed to just look at the other person for two minutes and also given an additional two minutes for chatting.

All the 140 people who took part were straight, as only a few gay people volunteered and their visits to the cabin didn’t coincide with each other’s.

Blind date science

Subjects were hooked up to sensors that measured their heart rate and skin conductivity and wore eye-gaze-tracking glasses, and all their body movements were recorded. At the end, they answered questions about the meeting, including whether they would like a real date, and whether they thought their partner would.

The researchers found there was no body language that predicted whether or not people liked their partner – including eye gaze, facial expressions, face touching and nodding.

Sometimes people did “mirror” each other’s behaviour – such as smiling or nodding when the other person did – but contrary to popular belief, there was no correlation between mirroring and whether there was any spark of attraction. The researchers have posted their findings to a preprint server ahead of formal peer review.

Sally Farley of the University of Baltimore says this contradicts previous studies. “There is a lot of literature that shows behaviour is highly predictive of attraction. Eye contact, proximity, touching, gestures, mimicry, voice – all of these things are behavioural indicators of attraction.”

However, the Dutch team did find that the more couples’ heart rate and skin conductance synchronised during their chat, the more attracted they became to each other. “There was no body language to tell you if your partner was interested – physiology is where we found much better estimates,” says Eliska Prochazkova, also of Leiden University.

People cannot generally control these internal features, says Prochazkova. “We can’t perceive the other person’s heart. But often our subconscious can be influenced by our physiology.”

The team also found that people were terrible at gauging their partners’ feelings. When asked to predict if their partner would like a date, they scored no better than random guessing.

But the answers did reveal a certain bias: if someone fancied their partner they were more likely to think that person liked them back, even though in reality there was no correlation. “People tend to be biased by their own feelings,” says Prochazkova. “It’s an interesting mind trick.”

The researchers also saw differences in men and women’s behaviour. The women smiled, nodded and touched their face more often, while men stared more at their partner’s head and eyes.

In addition, women were choosier. Only 34 per cent of the women said they wanted a date, compared with 53 per cent of the men.

As this coincided in just 16 per cent of couples, the experiment did not lead to many relationships. In these cases the researchers gave the pair each other’s contact details and left them to it.