Here's a fascinating study. By changing what was in front of the subjects on the questionnaire they were filling out, the subjects were tricked into believing that they believed the opposite of what they had just affirmed. What is fascinating is that a slight majority not only would read out loud and affirm that opposite (say that something is permissible, which they first said was not), but would go on to defend that in argument.
I wonder what they were asserting when they seemed to affirm the opposite to their initial claim. It's tempting to say that they were simply misspeaking and hence we should not attribute to them the assertion of something that they didn't believe. But then they defended what they literally said, which suggests that this is what they were asserting.
I guess I am inclined to think they weren't asserting contrary to their beliefs, but they were arguing contrary to their beliefs. Maybe this is another way of seeing that arguments come apart from why one believes what one does.