Short answers, pulled from the story.
Gordon Allport defined prejudice as a feeling, favorable or unfavorable, toward a person or thing, prior to, or not based on, actual experience. He also argued in his 1954 book The Nature of Prejudice that categorical thinking underlying prejudice is a normal and natural process of the human mind, not a pathology.
The word prejudice has been used in English since around the year 1300. It derives from the Old French préjudice, which came from the Latin praeiūdicium, a compound of prae (before) and iūdicium (judgment), meaning prior judgment.
The Robber's Cave experiment showed that prejudice and hostility between two groups of summer campers developed rapidly after they were placed in sports competitions for small prizes. The hostility decreased when the groups were required to cooperate on tasks toward a shared goal, supporting the realistic conflict theory.
The Implicit Association Test measures how much a person is prone to discriminate against a certain group unconsciously by evaluating hidden negative attitudes. In 2023 alone, more than 40 million IATs were completed at the Project Implicit website.
Walter G. Stephan's integrated threat theory identifies four threats that drive outgroup prejudice: realistic threats such as competition for resources, symbolic threats from perceived incompatible cultural values, intergroup anxiety felt during interactions with outgroup members, and negative stereotypes that prime expectations of bad behavior.
A meta-analysis of 515 studies involving roughly a quarter of a million participants across 38 nations by Thomas Pettigrew and Linda Tropp found that intergroup contact reduces prejudice mainly by lowering anxiety about contact and increasing empathy and perspective-taking. Increased knowledge about the outgroup also helped, though it was a weaker mediator than the other two.