money, risk our money. everything because it shows what's happening right up here. in the mri, volunteers are presented with different choices. keep a small amount or risk it to win more. by changing the dollar amounts at risk and the dollar amounts that can be gained, scientists are able to see how different areas of the brain react as decisions are made. >> there's an area we're very interested in called dorsal medial prefrontal cortex, the area in the middle, top and front of your brain, and that part of the brain seems to act as almost like a switch in a train yard or it's telling all the other parts of the brain that might contribute to a decision, which ones are going to be active at any moment in time. and so what it does is seems to switch between the more risk averse and risk-seeking mode depending on what's going on in the task at any moment in time. >> 140 and one, two, three, four. okay.