 There are different ways to come up with a research idea. Our came when my friend came back from a Tinder date. She said it was great. As they sat and talked, the conversation flew, and every time you look into her eyes, she felt these butterflies in her stomach. Her heart was racing fast, and she felt this spark, this mutual chemistry. But he never called back. When there was no spark, could she misinterpret his signals? So the question is, what is this spark? And how do you know that someone's attracted to you? We decided to put this question in test and invited 140 individuals to our dating cabin. When the date started, we measured couples' eye gaze, their facial expressions, their body language. We also tracked their heart rate and sweating responses. Throughout the date, we asked how they feel about each other. So what did we find? First of all, quite humorously, people are pretty bad in guessing whether their partner likes them or not. In fact, more people like somebody, more do you think their partner likes them back, while there is no correlation whatsoever. So what are the reliable signals that someone likes us? As it turns out, no single signal, like frequent eye contact, smile or gesture, were good predictors of people's attraction. Not even raising heart or sweating were good indicators. And this is because people flared just to be liked, and raising heart can just mean somebody's nervous. So is there a way to measure attraction between two people? In order to do that, we need to zoom out from the individual and look at a couple dynamic. What we found was that it was the synchrony between physiological signals that predicted couple's attraction. More the couple synchronized their heart rate and sweating responses with each other, attracted they become to each other. If you imagine that people's physiology is like a melody, oscillating between two partners, and more the couple synchronized, better the melody sounds, and more attracted they become towards each other. Next time your D doesn't call you back, don't worry about it. Remember, you might be a hard rock chick and he's a folklore, and if you try, you will always play out of tune. If you want to learn more about this research, follow me on social media.