People conform to social norms Which can cause prejudice. For example, homosexuality used to be illegal so in society it was ordinary to be prejudiced, but as norms have changed its more acceptable and less people are prejudiced.
Allport if situation is set up so that people in different groups can have contact, they can help reduce prejudice as they can find out their views. Making them corporate for superordinate goals and who are on equal footing as no group is higher than the other can help reduce prejudice
AO3evaluation:
Strength is supporting evidence. Akrami2009 found that after he changed the social norms about sexism in a university he found that there was less sexism in the campus, while the control group didn't find a change. This shows that social norms do affect prejudice.
Weakness is that it's reductionist as it considers nurture such as social norms but not nature such as personality traits so oversimplifies the explanation of prejudice down to just one factor