For centuries, the fleeting and highly subjective world of feelings was the purview of philosophers. But during the past 30 years, Antonio R. Damasio has strived to show that feelings are what arise as the brain interprets emotions, which are themselves purely physical signals of the body reacting to external stimuli.

Born in 1944 in Lisbon, Portugal, Damasio has been chair of the University of Iowa's neurology department since 1986. He and his wife, neurologist Hanna Damasio, have created one of the world's largest databases of brain injuries, comprising hundreds of studies of brain lesions and diagnostic images. As profound as some of the damage is to Antonio Damasio's patients, all of it informs his understanding of how emotions and feelings arise and how they can affect mental illness.

In recent years, Damasio has become increasingly interested in the role emotions play in our decision-making processes and in our self-image. In several widely popular books, he has shown how certain feelings are cornerstones of our survival. And today he argues that our internal, emotional regulatory processes not only preserve our lives but actually shape our greatest cultural accomplishments. --Interview by Manuela Lenzen

MIND: Professor Damasio, why are you so fascinated by the nature of human emotion?

Antonio R. Damasio: At first I was interested in all types of neurological injuries. If one area of the brain would lose its ability to function, the patient's behavior could change either dramatically or only subtly. One day I asked myself, What is missing in a person who can pass an intelligence test with flying colors but can't even organize his own life? Such patients can hold their own in completely rational arguments but fail, for example, to avoid a situation involving unnecessary risk. These kinds of problems mainly occur after an injury to the forebrain. As our tests prove, the result is a lack of normal emotional reactions. I continue to be fascinated by the fact that feelings are not just the shady side of reason but that they help us to reach decisions as well.

MIND: You differentiate between feelings and emotions. How so?

Damasio: In everyday language we often use the terms interchangeably. This shows how closely connected emotions are with feelings. But for neuroscience, emotions are more or less the complex reactions the body has to certain stimuli. When we are afraid of something, our hearts begin to race, our mouths become dry, our skin turns pale and our muscles contract. This emotional reaction occurs automatically and unconsciously. Feelings occur after we become aware in our brain of such physical changes; only then do we experience the feeling of fear.

MIND: So, then, feelings are formed by emotions?

Damasio: Yes. The brain is constantly receiving signals from the body, registering what is going on inside of us. It then processes the signals in neural maps, which it then compiles in the so-called somatosensory centers. Feelings occur when the maps are read and it becomes apparent that emotional changes have been recorded--as snapshots of our physical state, so to speak.

MIND: According to your definition, all feelings have their origin in the physical. Is that really the case?

Damasio: Interestingly enough, not all feelings result from the body's reaction to external stimuli. Sometimes changes are purely simulated in the brain maps. For example, when we feel sympathy for a sick person, we re-create that person's pain to a certain degree internally. Also, the mapping of our physical state is never completely exact. Extreme stress or extreme fear and even physical pain can be dismissed; the brain ignores the physical signals that are transmitting the pain stimulus.

MIND: The differentiation between emotions and feelings brings to mind 17th-century philosopher Ren¿ Descartes' idea of dualism--that the body and mind represent autonomous systems. But you reject that idea, as you explain in your book Descartes' Error. How should we see the relationship between mind and body?