How might game theory be applied to explain behavior that appears altruistic in nature?

The game theory explains the altruistic behavior of people. According to this theory, people help others only when they know they can get benefit from it. They start to rationalize that, the person whom he is helping is much capable to return something.  

The game theory is the best way to recognize people. Through this theory, people rationalize the behavior of people. They rationalize that the behavior is proper/ rational or not for others.

The altruism is is the behavior that acts according to the self-interest of people. The game theory is the theory that put the altruism in the frame of self-interest.