According to this study, if we think someone else is an expert at something, our own brains shut down and let that person take care of it. If we trust the person making the decision, our own decision-making apparatus turns itself off. Duh, right? But it's interesting to see the phenomenon presented so graphically in a brain scan.
It's like in marriages, if one partner is (or just seems to be, or we think he is or, etc.) very effective in some area, the other partner lets him or her take care of it. You know about cars, so you keep track of when to change the oil. You're better at math, you pay the bills. You cook, I'll wash the dishes. If one partner is hyper-functional in an area, the other partner gets less and less effective in that area. It just makes sense; division of labor makes a house hum.
Is this any more complex than our brains just looking for a break where they can find one? I often get frustrated with myself because if someone else is driving, I don't pay attention to where I am. So if I have to get there by myself next time, even if I've been there dozens of times I have no idea where it is or how to get there. This even happens when I'm walking with someone. If I think my companion knows the way, I stop paying attention. Trouble is, often that person and I are both thinking the same thing and we get totally lost. And it feels involuntary, it's as if I can't even make myself pay attention if I try.
I kind of see this study as evidence of something very nice about how we work together as organisms. We don't all need to be taking care of everything, do we? The discouraging aspect is, like so many things, the biological mechanism doesn't seem to take into account our infinite ability and desire to deceive each other.