Getty Images/Pascal Le Segretain Being with someone for a long time changes the way you see the world.
It also changes you.
More importantly, close relationships may spark an entirely different way of thinking and acting, something Joshua Wolf Shenk, author of "Powers of Two," chalks up to having a "shared mind."
So, how do you and your significant other stack up? Check out these signs psychologists have observed in long-term couples that they say point to having such a shared mind: