Case Closed? On the John F. Kennedy Assassination: Biased Assimilation of Evidence and Attitude Polarization

Vitriolic debate surrounds John F. Kennedy's (JFK's) death more than 30 years after the assassination. Whereas some endorse the official government conclusion that Oswald acted alone, others allege that some form of a conspiracy is responsible for Kennedy's death. The central thesis of this article is that due to the processes of biased assimilation and attitude polarization, personal theories about the perpetrator(s) of the assassination are essentially immutable, and therefore that the debate surrounding JFK's assassination will continue endlessly. Due to the process of biased assimilation, proponents of both the Oswald and conspiracy theories perceive the same body of evidence as supportive of their position. Biased assimilation leads to attitude polarization rather than to a moderation or reversal of existing attitudes. The results of the present study strongly support this line of reasoning. The study also examined the formation of assassination attitudes among subjects with no initial opinion. The majority of these subjects embraced the conspiracy theory at the conclusion of the study. However, authoritarianism was indirectly associated with the development of an Oswald theory stance via an increased endorsement of evidence consistent with the Oswald theory.