that repeating the message several times makes consumers more likely to purchase the product because they already connect it with a good emotion and positive experience. Stefano DellaVigna and Matthew Gentzkow did a comprehensive study on the effects of persuasion in different domains. They discovered that persuasion has little or no effect on advertisement; however, there was a substantial effect of persuasion on voting if there was face-to-face contact. Cognitive dissonance theory Leon Festinger originally proposed the theory of cognitive dissonance in 1957. He theorized that human beings constantly strive for mental consistency. Our cognition (thoughts, beliefs, or attitudes) can be in agreement, unrelated, or in disagreement with each other. Our cognition can also be in agreement or disagreement with our behaviors. When we detect conflicting cognition, or dissonance, it gives us a sense of incompleteness and discomfort. For example, a person who is addicted to smoking cigarettes but also suspects it could be detrimental to their health suffers from cognitive dissonance. Festinger suggests that we are motivated to reduce this dissonance until our cognition is in harmony with itself. We strive for mental consistency. There are four main ways we go about reducing or eliminating our dissonance: changing our minds about one of the facets of cognition reducing the importance of a cognition increasing the overlap between the two, and re-evaluating the cost/reward ratio. Revisiting the example of the smoker, they can either quit smoking, reduce the importance of their health, convince themself they are not at risk, or decide that the reward of smoking is worth the cost of their health. Cognitive dissonance is powerful when it relates to competition and self-concept. The most famous example of how cognitive dissonance can be used for persuasion comes from Festinger and Carlsmith's 1959 experiment in which participants were asked to complete a very dull task for an hour. Some were paid $20, while others were paid $1, and afterwards they were instructed to tell the next waiting participants that the experiment was fun and exciting. Those who were paid $1 were much more likely to convince the next participants that the experiment really was enjoyable than those who received $20. This is because $20 is enough reason to participate in a dull task for an hour, so there is no dissonance. Those who received $1 experienced great dissonance, so they had to truly convince themselves that the task actually was