To feel superior
According to Alfred Adler, the father of individual psychology, all people strive to be superior. When a person fails to feel superior in a useful way, he might attempt to feel superior by putting others down, criticizing them or discriminating against them.
Colonization could have contributed towards racism
Colonization, or the act of establishing a colony in a new country, might have contributed towards racism. Europeans formed many colonies in different countries, and as a result, the white skin of Europeans was considered by some people the sign of superiority.
To belong to the superior group (according to their beliefs)
Humans always want to belong to a superior group to feel good about themselves. The fact that some people discriminate against blacks made some of the white people, who wanted to feel better about themselves, to do the same to belong to a group they believe to be superior.
Stereotypes can affect performance
A study found that if a person was reminded of racial discrimination against his race before an exam then he is likely to perform worse in the exam. According to the study, people who believe in the racial stereotypes imposed on them might prove them correct. (See Why are some people so racist?)
Fear of the unknown
Some psychologists believe that at the heart of discrimination lies the fear of the unknown. A normal person would like to understand everything around him, and when he finds people who are different his fear can motivate him to discriminate against them.
A superiority complex
A person who has a superiority complex usually believes he is superior to others in order to cover his deep down inferiority. (See Why do people strive for superiority?)
Social Darwinism might have led to racism
According to Wikipedia, Social Darwinism is a theory that applies the rules of natural selection to sociology and politics. People who believe in this theory believe that the strong should see their powers and wealth increasing, while the weak should experience the opposite.
The media set beauty standards to whites
According to psychologists, our attractiveness perception is very plastic and can be affected by the media and what we see on TV. The media has made white people the new beauty standard and so some white people started feeling superior to blacks.
Because of the history of slavery
The new European traders took black slaves to work in their new colonies. As a result of being seen as slaves, some people assumed that blacks were inferior to white people.
Because most advanced countries in this era have white people as a majority
People who didn’t study history and who just saw a snapshot of the current world might assume that black people are inferior because most advanced countries have white people as a majority.
Some scientists tried to make some studies to prove that blacks are inferior to whites. The fact that some of those studies got some powerful propaganda unconsciously made some people believe that blacks are inferior.
Some people need racism to be psychologically healthy
In order to feel better about themselves, people who usually have self-esteem problems need to discriminate against any group they believe to be inferior to feel better. This is why people discriminate against race, religion and women.
Each person wants his group to be superior
Humans like to believe that the group they belong to is superior. This is why both iPhone and Android users usually consider each other inferior. The desire to make one’s group superior is hard wired into the human brain.
Majorities usually discriminate against minorities
Blacks are a minority in the United States, and as a result, white people are more likely to discriminate against blacks since they are the minority.
The desire to conform to social norms can lead to discrimination
In one study, it was found that the desire to conform to the acceptable social norms can either make people nice or unfriendly to minority groups. According to the study, if in one city white’s discriminate against blacks then many other whites will join just to conform to their group’s behavior.
They truly believe those people are inferior
People who have false beliefs about others might discriminate against them. A person, for example, who believes that obese people are lazy might discriminate against them. A person’s belief system can make him a racist.