So here's something totally random: Men feel emasculated when another man holds the door open for them.

A new two-part study in the Journal of Social Influence first looked at how people open the door for others; either by walking through it and holding it open for the person behind, or holding the door and letting someone else go first. They found that men were less likely to have the door held for them in the second way.

In the next experiment, researchers gave men a brief survey after they walked through a door (some had it held open while others opened it themselves). The men who had the door opened for them surprisingly reported significantly lower self-esteem and self-efficacy (basically, confidence in your ability to achieve things) than those who opened it themselves.

Weird.

Holding the door is only polite, and in no way emasculating. But it apparently had an effect on these men. So guys, if you want to make a rival feel like shit, just open and hold the door for him.