Cognitive dissonance has traditionally been defined as the negative affective state which accompanies inconsistent cognitions and motivates one to make the cognitions consistent. This thesis critically evaluates two theories about cognitive dissonance. The action-based model of dissonance argues that inconsistent cognitions have the potential to interfere with effective and unconflicted action. The new look model of dissonance, contradicting the traditional definition of dissonance, argues that it is aversive consequences rather than inconsistent cognitions that cause dissonance. Recent studies investigating the neural correlates of dissonance show that parts of anterior cingulate cortex and prefrontal cortex seem to be involved in the dissonance process. One of the major predictions of the new look model of dissonance has been undermined by recent evidence. In contrast, the action-based model of dissonance is supported by recent studies.