I need to test my ability to do cool things with blogs (insert links, embed videos, include pictures, etc.), but I want it to relate to psychology, so I chose cognitive dissonance, one of my favorite topics from my social psychology class.
Leon Festinger ("Uncle Leon") was the psychologist to originally study and identify the phenomenon and develop the theory, along with his colleague J. Merrill Carlsmith. In this seminal experiment, subjects performed a menial and unenjoyable task of turning spools and then asked to tell the next subject how fun the task is. Half of the subjects were paid $20 to do this reporting task; the other half were paid $1. A feeling of anxiety (cognitive dissonance) would arise from the discrepancy between their actions (the unenjoyable task) and their statement that the task was enjoyable. The theory goes that those paid $20 would find the 20-dollar payment to be a sufficient justification for lying; on the other hand, those paid only $1 would not find this to be sufficient justification, so they would change their opinion of the task in order to eliminate the dissonance.
However, the entire scientific community was not convinced by these findings. Daryl Bem did not believe the effects to be due to any sort or emotion or anxiety; rather, he believed the effects could be explained with he termed the self-perception theory. Bem's theory is as such: when we observe others, we do not have access to their emotions or thoughts, so we strictly analyze their environment and actions; when we when our actions are in discord with out cognitions, rather than reducing an anxiety, we achieve an attitudinal change after analyzing ourselves as analytically as we would observe another. To test this theory, Bem employed the same paradigm as the Festinger study, with one exception: instead of doing the task and reporting, subjects were told about Bob who had done the task and was paid to say it was fun. Subjects were then asked to evaluate how much Bob enjoyed the task. As can be shown in the table below, Bem found the same results as Festinger; but because Bem's theory does not rely on the added assumption of arousal, the principle of parsimony would argue his to be the better theory.
Still, the debate was not over. There were still people who believed in cognitive dissonance. There was also no reason to believe both couldn't be true--perhaps dissonance is employed when we judge ourselves, perception when we judge others--so in an exquisite experiment (one of my favorites, because of its beautiful design and explanatory prowess), Fazio, Zanna, and Cooper (1977) pitted the theories against one another. Subjects with liberal beliefs had to write essays arguing for specific topics, either something they would agree with or not agree with. They found writing a belief-consistent argument did not change their beliefs but that writing a belief-inconsistent essay could change their opinions, but only if there was a high choice (so they would have to know that they chose to write the essay voluntarily) and they had no external factor on which to blame their internal anxiety. However, if the choice was high but they had an external stimulus that caused discomfort/arousal (in this case, an uncomfortable booth), the internal arousal would be attributed to the booth rather than the behavior-cognition inconsistency and they did not change their beliefs. (I know it's complicated. You can read the full study here, if you like.) Self-perception would not predict that, thus restoring cognitive dissonance to its former glory.
That is not to say that self-perception is invalid or has no validity for predicting how our behaviors affect our attitudes. Take the facial feedback hypothesis, for example; affect/attitude is affected, but you can't argue that any dissonance is present. There are other instances where self-perception seemingly succeeds in explaining what cognitive dissonance cannot. Thus, as David Myers puts it in his textbook on social psychology, "Dissonance theory, then, explains attitude change [...] self-perception theory explains attitude formation."