Cognitive dissonance is the feeling one gets when one does something that contradicts his or her beliefs. It can be a strong and distasteful feeling, and researchers have found that it can affect a person's judgment.
Funnily enough, this was tested by having people dress up as Carmen Miranda, the Chiquita banana lady. In a grass skirt, coconut bra, and fruit-laden headdress, subjects walked in broad daylight across a campus quad, then asked to estimate the distance they traveled. Some of the subjects were made to believe they had a choice in wearing the costume or doing some unnamed embarrassing thing, while others were given no choice. There was also a control group who didn't wear the costume at all.
Those who chose to wear the outfit tended to estimate the distance much shorter than those who were forced to wear it. Those not in outfits estimated right in the middle of the other two. The cognitive dissonance of having to dress up in an embarrassing costume caused the brain to judge distance longer than if there was a choice or if there was no outfit. Perhaps this is because the uneasy feeling made people feel like time was dragging on, so the distance seemed longer. Or perhaps because those subjects felt put-upon, they imagined the task to be harder and the embarrassment longer lasting. At any rate, there is a definite indication that cognitive dissonance affects the judgment of the physical world.