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Followers of passion

THE NEW INTEREST in the relationship between emotion and thinking has fueled a growing body of research. Even when we are doing the most mundane things -- like shopping or playing cards -- our unconscious emotions are influencing our decisions and shaping our judgment. As David Hume put it, "reason is, and ought to be, the slave of the passions."

Thinking, without feeling. Antonio Damasio, then at the University of Iowa, described the experience of neurological patients unable to experience emotion. While these patients all appeared perfectly intelligent, and showed no deficits on any conventional cognitive tests, they had tremendous difficulty making "rational" decisions. (Published in Behavioral Brain Research, 1990)

Fear before awareness. Joseph LeDoux of NYU painstakingly traced the nerves connecting the auditory sensations of rats to various parts of the brain. He found that frightening stimuli were processed by the emotional parts of the brain before they were processed by the cortex, the seat of conscious thought. This "low-road" of sensory processing is almost twice as fast as the "high-road." As a result, we experience strong emotional reactions before knowing what, exactly, we are reacting to. (Journal of Neuroscience, 1990)

The smarter unconscious. Following up the work with "emotionless" patients, scientists at the University of Iowa set up a simple card game and measured emotional responses. They found that the feelings generated by the unconscious brain often figured things out before the conscious mind, and that these feelings helped the players make money. But the "emotionless" patients, who did not have the benefit of these feelings to guide their thinking, often went "bankrupt" before the game was over. (Science, 1997)

Moral feelings. Harvard's Joshua Greene imaged the brains of people contemplating various types of moral dilemmas. He discovered that personal moral situations -- these involve directly hurting somebody else -- trigger a specific subset of emotional brain areas, which discourage potential acts of violence. (Science, 2001)

Impulsive decisions. Researchers at Princeton asked people whether they wanted a low-value gift certificate right away or a higher-value certificate in a few weeks. They found that when people started thinking about getting a gift certificate right away, brain areas associated with emotion were turned on. These impulsive feelings led people to opt for the spoils of immediate gratification. Scientists hope that this research will help them understand why people make bad financial decisions, such as not saving enough money for retirement. (Science, 2004)

The emotional mall. Researchers at Stanford turned their brain scanning machine into a virtual shopping mall, recording people's responses as they struggled with purchasing decisions. Each decision, they found, activated two separate emotional brain areas. One area was excited by the pleasant prospect of getting something new. The other area was triggered by the price tag, and generated a negative emotion. This emotional tug-of-war determined what was bought. (Neuron, 2007)