Scientists are finding you can’t make “rational” decisions without emotion:

Antonio Damasio, a neuroscientist at USC, has played a pivotal role in challenging the old assumptions and establishing emotions as an important scientific subject. When Damasio first published his results in the early 1990s, most cognitive scientists assumed that emotions interfered with rational thought. A person without any emotions should be a better thinker, since their cortical computer could process information without any distractions.

But Damasio sought out patients who had suffered brain injuries that prevented them from perceiving their own feelings, and put this idea to the test. The lives of these patients quickly fell apart, he found, because they could not make effective decisions. Some made terrible investments and ended up bankrupt; most just spent hours deliberating over irrelevant details, such as where to eat lunch. These results suggest that proper thinking requires feeling. Pure reason is a disease.

Scientists are now finding more examples of emotional processing almost everywhere they look. A study led by Brian Knutson of Stanford University, published last January, demonstrated that our daily shopping decisions depend on the relative activity of various emotional brain regions. What we end up buying is largely dictated by these instant feelings, and not by some rational calculation.

In 2004, Harvard psychologist Joshua Greene used brain imaging to demonstrate that our emotions play an essential role in ordinary moral decision-making. Whenever we contemplate hurting someone else, our brain automatically generates a negative emotion. This visceral signal discourages violence. Greene’s data builds on evidence suggesting that psychopaths suffer from a severe emotional disorder — that they can’t think properly because they can’t feel properly.

“This lack of emotion is what causes the dangerous behavior,” said James Blair, a cognitive psychologist at the National Institute of Mental Health.