If you let your mind get caught in a loop of thinking, these girls will trigger a sort of philosophical optical illusion about the self. On the one hand, if their brains are indeed connected and sharing information, they have one – very unusual – brain. So using a neural definition of the self, that means they’re one person. But when you see them on video you experience them – as their mother does – as having two minds. Using a mental definition of self, that means they’re two selves. But then you realize these two selves have one brain… and back again you go to the beginning. And that’s the optical illusion. Depending on whether you define the self using minds or brains, you see a different number of people: One. Two. One. Two. The purpose of this illusion, which I submit should be called the “Neuroself Illusion,” is not to get you to choose one or two. Rather, it is to introduce you to the very real possibility that neuroscience does not support our four-hundred year-old Enlightenment assumption that each of us has a single self. Rather, neuroscience – mixed with simple logic – makes it increasingly likely that we will conclude the brain makes multiple selves or – if you think that idea makes no sense – no self at all. But either way we’re in for a cultural (but not a scientific!) paradigm shift. Because both conclusions rock western society’s core metaphysical assumption: that an individual self, in an individual body, is what we really are. Increasingly, the smart money says it ain’t.