Cialdini and his colleagues (1976) counted the number of college insignia T-shirts worn by ...

Cialdini and his colleagues (1976) counted the number of college insignia T-shirts worn by university students on the Monday after their teams played football.
 
  These researchers found that students were more likely to wear such shirts after victories than after losses. These findings suggest that
  a. in-group identification is a source pride and self-esteem.
  b. minimal categorization can have effects on competition.
  c. in-groups can provide support after setbacks.
  d. the establishment of in-group bias can contribute to intergroup conflict.