Why are you surprised?
Martin points us to: Call for neuroethics as brain science races ahead
The only surprising thing about our ability to understand the decision making process is that it took so long. There are no magic tricks going on inside of our brains... a magical little elf who mysteriously decides to buy this cola instead of that one... it's just grey goo and the hard part was getting a good enough look to figure it out. Thanks to scanning technology, they're starting to do just that.