I remember watching the MythBusters a few years back when they where testing whether having your windows down or having your air conditioning on was better for fuel economy in your car. I immediately wanted it to result in better fuel economy to have the windows down, simply because I prefer to have the windows down to using the air con. I had no logical reason for this reaction, simply knowing would be better then I could make an informed decision, but instead I was automatically looking for reasons why the air con would be less efficient and the extra drag from the windows negligible.
This anecdote illustrates an important facet of human nature: we naturally look for the result we'd prefer to see. All humans are prone to this in some situations. It is for instance prevalent in the Creation/Evolution debate; Christians have an instinctive tendency to look for evidences, or interpretations thereof, that support a recent creation of the Earth, while Atheists have the exact same tendency to look for the opposite. The reason for this is of course obvious: no one likes to have their entire sincerely held worldview shattered. This is of course only one example; the same sort of issues arise in all areas of human knowledge to some extent or another.
I suspect that everyone demonstrates this bias, at least in some areas, and in some fields of study it is probable that no one is immune to it. Any one who claims otherwise is most likely telling mistruth, either they are being deliberately deceptive, or they are unaware of their own thinking, which means their thinking is suspect. We cannot, after all, overcome our own biases unless we are aware of them. Ultimately we most consciously watch for and correct our own biases to prevent our own thinking from becoming faulty or limited.
PS: In the MythBusters', admittedly limited and un-scientific, testing it was concluded that having your windows down was better for your fuel economy, so it turned out I was right all along. :-)
