* People feel closer when they do new things together.
* Emotional bonds are strengthened when people do physical activities together.
* People tend to bond when they’re in frightening situations together.
* Feelings of love grow when total strangers simply gaze into each other’s eyes for two minutes.
Emotional bonds often get stronger when people feel vulnerable, and this works for two reasons. First, when you see someone who is in a weak and vulnerable state, you often feel like comforting or protecting that person; those tendencies make you feel close to them, and they often bring you physically closer, too. Second, when you are feeling vulnerable yourself, you could interpret your emotional state as a loving one—especially if someone nearby happens to reach out to comfort you. If two people feel vulnerable simultaneously, these two tendencies can interlock and increase synergistically.
Most of the experiences that lead to increases in emotional intimacy produce this kind of dynamic. Strong sexual attraction, scary situations, vigorous exercise and novel situations all make people feel vulnerable to some extent. And, yes, even gazing can have this effect. The difference between mutual gazing and staring is consent; people are giving each other permission to invade their privacy in a way that is normally quite threatening.