If you want someone to open up to you, just make them laugh. Sharing a few good giggles and chuckles makes people more willing to tell others something personal about themselves, without even necessarily being aware that they are doing so. These are among the findings of a study led by Alan Gray of University College London in the UK, published in Springer's journal Human Nature.

The act of verbally opening up to someone is a crucial building block that helps to form new relationships and intensify social bonds. Such self-disclosure can be of a highly sensitive nature -- like sharing one's religious convictions or personal fears -- or a superficial tidbit such as one's favorite type of food.

To investigate the role and influence of laughter in this disclosure process, Gray and his colleagues gathered 112 students from Oxford University in England, into groups of four. The students did not know one another. The groups watched a 10-minute video together, without chatting to one another. The videos differed in the amount of laughter they invoked, and the amount of positive feelings or emotions they elicited. One featured a stand-up comedy routine by Michael McIntyre, another a straightforward golf instruction video, and the third a pleasant nature excerpt from the "Jungles" episode of the BBC's Planet Earth series. The levels of laughter and the participants' emotional state after watching the video was then measured. Each group member also had to write a message to another participant to help them get to know each other better.

The participants who had a good laugh together shared significantly more intimate information than the groups who did not watch the comedy routine. Gray suggests this is not merely because it is a positive experience, but because of the physiology behind a good laugh. It actually triggers the release of the so-called "happy hormone" endorphin. The findings support the idea that laughter encourages people to make more intimate disclosures to strangers.

Interestingly, the person who disclosed information was seldom aware that he or she had done so. It was only the listener who realized that it had happened.

"This seems to be in line with the notion that laughter is linked specifically to fostering behaviors that encourage relationship development, since observer ratings of disclosure may be more important for relationship development than how much one feels one is disclosing," says Gray. "These results suggest that laughter should be a serious topic for those interested in the development of social relationships."