When given the option of either kicking your grandmother down a flight of stairs or selling her car because you know she is too forgetful to know it was gone, one might find it difficult and uncomfortable to make a decision. Why? The question is simple, it is really only flipping a coin in many ways. In either choice grandma looses and get hurts. What about a third option where no one gets hurt, that will make this easier. So, you can kick grandma down the stairs, sell her car for your gain, or have sex with her dead body by her request. I am still finding it difficult to make a choice.
The reason pinning these questions against each other is so difficult is because they don't work on the same areas of the brain. The first example one would be causing harm, the second is being dishonest, the third fills one with disgust and all three activate separate neuropathways. After the brain has invoked all these different pathways it sends the message up to the frontal lobe so it can figure it out. As a result, we are left in conflict, mostly because we are trying to sort out all the different signals.
Carolyn Parkinson and colleagues, recently published an article that explained the differences in activation. The approached used by her team is interesting because it addresses all levels of morality, things being natural or not neutral (stealing from grandma is wrong but what about finding out you didn't pay for the dog food on the bottom of your cart once you get home.) and all the different types of situations used above.
If you would like to read about the specifics of the study including what regions were activated and how they tested the subject (some of the questions at the bottom are pretty silly), the link is posted below
MIT Press Journal