Disgust reactions to sex can be arbitrary, personal, and defensive. They can be quite different in different countries, subcultures, and time periods. The examples of felching and sounding show the fine line between disgust and fascination. Even the exchange of sex for material goods arouses different reactions depending on the context. While psychoanalysis has opened up the discussion of varying sexual practices, it has also espoused cultural and religious norms of sexuality that have sabotaged clinical effectiveness. Research may help clarify how the same act can at different times seem silly, repugnant, or world changing.