Wikipedia says: "In sociology and social psychology, an in-group is a social group to which a person psychologically identifies as being a member. By contrast, an out-group is a social group with which an individual does not identify." Implying it is about psychological identification. This makes sense for groups like...
For many conventional things that are considered standard "stereotypes" about groups such as physical appearance-related assumptions about sex or gender, age, race, nationality, or style of dress, accent etc., that the general public employs? On the one hand, those in the rationality community emphasize the point to use whatever information...
Here's a phenomenon I was thinking about. In many situations, knowledgeable people don't just go out of their way to show off how much they're familiar with things that raise their clout with the ingroup -- for example, an artsy person rattling off names of obscure artists to his artsy...