Preference for group members with similar genes

Second, reciprocal altruism.

1, obey a social rule

Step 2 subtract the potential discomfort

3. Psychological satisfaction of external social identity.

Third, selfless altruism.

I am more willing to show selflessness and altruism when I am in a good mood.

Bystander effect:

The number of onlookers on the scene affects the possibility of pro-social reaction in real emergencies. When the number of onlookers increases, the possibility of any bystander providing help will decrease, and even if there is a response, the response time will be prolonged. The more people there are, the greater the influence of external environment on individual behavior and choice in the crowd. The higher the population density, the less likely it is to help others.