Psychologists discovered a weird trick to gaining people's trust

Looking deep into your conversation partner's eyes isn't just for lovers - it has a place in the conference room, too.

That's according to new research, which found that people are more likely to trust others with dilated pupils.

In the study, led by Mariska Kret, Ph.D. of Leiden University, 69 students at the University of Amsterdam played an investment game in which they watched short video clips of their "partner." It was actually a manipulated image of a pair of eyes, which showed pupils that dilated, constricted, or stayed the same over four seconds.

Next, the participants had to decide whether to give five Euros or zero Euros to their partner. Researchers told participants that their investment would be tripled, and their partner would choose how much of that sum to give back to the participant. (The researchers were really the ones determining the partners' choices, since the partner was just a computerized image of eyes.)

Results showed that participants gave more money to partners whose pupils dilated, especially when the eyes looked happy. The researchers interpreted these findings to mean that participants were more likely to trust people with dilated pupils.

In a release, Kret said it's impossible to voluntarily dilate or constrict your pupils. Yet other recent research suggests that simply thinking about a dark room can make your pupils dilate to take in more light.

That could be a useful trick when you sense that someone doesn't trust you - imagine yourself in darkness and hope that your partner notices the change in your eyes.

Interestingly, the study also found that most participants mirrored their partners' pupils, either dilating or constricting their own. When they mimicked dilation, they were more likely to invest money, unless the partner looked Asian as opposed to Western European.

That means that you might be able to tell if someone trusts you by looking closely at their eyes. 

"Possibly, when humans unconsciously mimic the dilations of another's pupil, they come to feel reflections of that person's inner state, which signals mutual interest and liking," the researchers write. "This process could facilitate calibrated and fast decisions in interactions with strangers."

This research does not imply that you should focus all your attention on your eyes instead of on what you're actually saying. But this study is just one more piece of evidence that much of interpersonal communication doesn't involve language at all.

Whether you're trying to convince someone to invest in your company or choose you as a job candidate, it helps to be aware that your words aren't the only factor involved in their decision.