The law of reciprocity means that when someone does something nice to you, you feel compelled to do something nice in return. For example, someone holds a door open for you, and you feel compelled to say thank you and smile. Yes, this is also good manners too, but for most of us feel that we want to say thank you as someone has done something nice. If someone gives us a gift out of the blue, we might feel compelled to think of something we can give them in return. Obviously there are takers in life who take everything [...]