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Despite the hole in his skull, the survivor returned home ten weeks after the accident. He even tried to resume work less than a year later. But as his coworkers mentioned, something had changed: “Gage was no longer Gage!”

Before the accident, he was a respectful and polite person, in addition to being a dedicated and efficient employee mostly held in high esteem. Afterward, his behavior changed dramatically. He became prone to intemperate outbursts, spiteful to others, and impatient. His inability to hold to a plan for future actions and his overall lack of “emotional control” ended up costing him his job.

Gage’s case, later popularized by neurologist Antonio Damasio in his best-selling book Descartes’ Error,5 is one of the first-known demonstrations that the frontal areas of the brain play a key role in rational behavior by “controlling” emotional reactions.6 But one can wonder if, reciprocally, emotions participate in rational behavior.

This is where neuroeconomics7 comes into play.

WHAT CAN WE LEARN FROM THE MARRIAGE OF ECONOMICS AND NEUROSCIENCE?

Today, this multidisciplinary field—which brings together economics, neuroscience, psychology, philosophy, sociology, and physics—is offering new empirical and theoretical insights on how emotions and rationality interdependently sha(r)p(en) our decisions. Among the most striking examples are a couple of neuroscientific studies of a familiar experimental economic setting, the Ultimatum Game (UG). The first of these was conducted by scientists at Princeton University in 2003.8 Alan Sanfey, Jonathan Cohen, and colleagues used functional magnetic resonance imaging (fMRI)9 in order to estimate the brain activity that occurs when people decide to accept (or not) an unfair share of money in the UG.10 From a purely rational view, whether a proposition is unfair or not should not make any difference to their decision—they would get more money by accepting than by rejecting it. Still, these UG experiments have shown repeatedly that many of us prefer what we consider a “fair” offer that earns us less money over an “unfair” one with a higher outcome. This setting constitutes a good illustration of an “irrational” economic decision.

FIGURE 10.1 Some of the Brain Areas Showing Increased Activity When Refusing an Unfair Offer in the Ultimatum Game Note: These are not actual experimental data but 3D reconstructions generated courtesy of Brain Voyager© for illustrative purposes.

Functional magnetic resonance imaging reveals a significantly higher brain activity in the dorsolateral prefrontal cortex, or DLPFC (considered one of the “rational” parts of the brain), the anterior insula (considered one of the emotional parts), and the anterior cingulate cortex (a kind of mediator between emotion and cognition) when the decision to refuse an unfair offer is made, as opposed to accepting it (see Figure 10.1). Thus it appears that both parts of the brain, respectively identified as rational and emotional, are involved in the final decision—corroborating the emo-rational hypothesis.

However, only the evolution of activity in the more “emotional” part of the brain (the insula) allows us to predict whether an unfair offer will be accepted or not. One could therefore be tempted to conclude that the “emotional brain” somewhat prevails over the more “rational brain” when such decisions are being made. In fact, reality is a bit more complex than this, as a second experiment has revealed.

Neuroscientists are capable of imaging the brain while it thinks, calculates, and decides. But they can also alter brain functioning by simulating lesions. 11 Daria Knoch, Ernst Fehr, and their colleagues at the University of Zurich recently investigated whether decisions in the UG would be affected if one of the so-called—or so-believed, I should say—rational parts of the brain (the DLPFC) were “asleep” for a little while. If rationality is temporarily in the “off mode,” one would logically expect emotions to take over, irrational behavior to