Anxiety/Uncertainty Management (AUM) theory was introduced by William B. Gudykunst to define how humans effectively communicate based on their balance of anxiety and uncertainty in social situations. Gudykunst believed that in order for successful intercultural communication a reduction in anxiety/uncertainty must occur. This is assuming that one person within the intercultural encounter is a stranger. AUM is a theory based on the Uncertainty Reduction Theory (URT) which was introduced by Berger and Calabrese in 1974. URT provides much of the initial framework for AUM, and much like other theories in the communication field AUM is a constantly developing theory, based on the observations of human behaviour in social situations.