The Outgroup Homogeneity Effect is the tendency to view an outgroup as homogenous, or as “all the same,” whereas the ingroup is seen as more heterogeneous or varied.
For example, a woman who lives in a big city might believe that everyone from the country or a small town is stupid, whereas she thinks that people from the city can be smart, stupid, or something in between. When the woman meets a small town person who is very intelligent, she considers him or her an exception to the norm. Overgeneralizing in this way about outgroup traits contributes to stereotyping.