A Social Group Decides That the Length of Someone's Big

A social group decides that the length of someone's big toe represents how intelligent and trustworthy that person is. Soon those with longer big toes have a higher social standing. Though the criteria may seem silly, it becomes a very real way group members are differentiated. This illustrates which sociological concept?

A) intersubjectivity
B) Thomas theorem
C) in-group
D) reference group