Anatomy of Give and Take
In other words, the brain is always one step ahead of itself, calculating the potential costs and benefits of each choice at a cellular level.

"Most of the brain is dominated by automatic processes, rather than deliberative [thinking]. A lot of what happens in the brain is emotional, not cognitive," said George Loewenstein, a behavioral economist at Carnegie Mellon University.

Some brain cells are especially sensitive to the potential rewards of decisions, research at Baylor and Emory University suggests.

Brain cells that release a chemical called dopamine, which serves as a reward to reinforce behavior, actually anticipate snap decisions to help balance costs and payoffs. The cells secrete a burst of good feeling beforehand to underline the desirability of one course of action versus another.

These neurons respond selectively. Some react only to the possibility of something beneficial and others only to the reward itself, researchers at the University of Fribourg in Switzerland discovered.

Every brain is of two minds about the future.

Two competing neural systems interact during choices that hinge on a conflict between short-term and long-term benefits, Harvard University researchers reported.

"Our emotional brain has a hard time imagining the future, even though our logical brain clearly sees the future consequences of our current actions," said Harvard economist David Laibson. "Our emotional brain wants to max out the credit card, even though our logical brain knows we should save for retirement."

Moral dilemmas can engage the same sense of fair dealing and mutual obligation as money matters. Researchers at Princeton University determined that synapses active during complex moral choices tapped into areas associated with rational thinking — and also into regions aroused by strong emotion.

"Some of that emotional architecture affects decisions we make involving money," Zak said.

Critics have often argued that volunteers playing experimental games in brain scanners are no measure of real market behavior. So researchers led by Lo at MIT studied working traders during their normal business day.

To measure brain activity indirectly, he wired 10 currency speculators at a Boston brokerage to sensors monitoring heart rate, breathing, blood pressure, body temperature and skin conductivity. By the end of the day, the traders had made 1,200 split-second trades, averaging $3 million to $5 million apiece.

His team plotted the biological indicators of stress, exuberance and tension against real-time profit and loss. He repeated the experiment at the Boston Stock Exchange.

Market trades, the sensors showed, were the stuff of sweaty palms, heavy breathing and pounding pulses. Snap judgments, honed by intuition, outweighed high-minded economic calculations.

These were "gut" decisions.

Contrary to traditional economics — which considers only rational deliberation — such measures of market panic and exultation begin to document how involuntary emotions affect the rise and fall of stocks.

Already, preliminary findings about the balance sheet of the brain have scholars rethinking the meaning of money itself.

The same reward circuitry activated by cocaine, sports cars, attractive faces and jokes is activated by money. Until now, economists have assumed that money was prized not for itself but only for what it could buy.

Moreover, the prospect of winning money activates specific brain regions in a way that the threat of losing it does not, researchers at Stanford University recently demonstrated.

Scientists are not sure how the electrical snap of synapses adds up to a financial decision, or how these insights might be assembled into a working theory of economic behavior.