The greatest challenge for all societies, regardless of how advanced they are, is to ensure and protect the collective welfare. This challenge arises from the fact that the interests of the collective do not necessarily coincide with the personal interests of the people belonging to that collective. Thus, on many occasions, people face a dilemma between furthering the collective interests or furthering their personal interests. Despite this 'dilemma', empirical research has consistently shown that people frequently cooperate with each other, even if they do not know each other. My research is aimed at answering the question why people cooperate with others.