Others have mentioned the idea of similarity and relatedness, indicating that a person is more likely to help another based on a genetic appraisal of the situation and the desire to help those of his or her specific gene pool. Another prosocial idea is that persons behave according to the theory of reciprocal altruism, in which persons help others in the expectation of receiving something in return. Persons might also help others when faced with guilt or the need to repay a good deed that was previously done to them. This is known as guilt or reparative altruism (Wetering).
On the other hand, situations exist in which persons might not be inclined to help. Situations of moralistic aggression may arise, in which people feel that others are taking advantage of their altruistic tendencies, and in such cases they might not be inclined to help. Such is often the case in larger cities where cheaters are apt to exist. Subtle cheating and mimicry abound, through which people might pretend to be in distress in order to elicit altruistic behaviour. Such situations are likely to cause moralistic aggression to arise in persons as a protective mechanism (Wetering).
The social setting also determines the type of behaviour one can expect from a person. According to the Darley and Latané study done in 1968, a person is more likely to help another if he or she is the only available helper in the situation. This theory is akin to others concerning crowds. Areas that are crowded or busy tend to contain people who are less likely to help in a dire situation. This might be due to their being in a hurry or it might hinge on the idea that crowds or busier areas are more likely to contain opportunistic persons. In such cases patterns might also obtain so that despite such variables as cultural or societal norms, in a crowd, the bystander