Humans have always been intensely interested in the workings of their own minds. But until about 100 years ago, the mind was more appropriately a subject for philosophers than for scientists, because the tools to study the brain did not yet exist. Through the first half of the twentieth century, the mind was treated by psychologists as a "black box" which internal workings could be deduced only through the investigation of how past and present experiences were interpreted and influenced behavior. New discoveries however are rapidly changing our views of the workings of the brain.

During recent decades, we have begun to understand the neural bases of at least some psychological phenomena. Many forms of mental illness, such as schizophrenic depression, and autism, once thought to be a childhood trauma or inept parenting, are now recognized as the result of biochemical imbalances in the brain. Studies are revealing a strong heritability factor for traits that were once considered entirely learned, such as shyness and alcoholism.

A striking illustration of how the physical structure of the brain is related to personality was unwittingly provided by Phineas gage in 1848. An explosion propelled a large metal rod through his skull, removing his left temporal lobe. He miraculously survived, but his personality changed radically. Before the accident, Phineas was conscientious, industrious, and well liked. After his recovery, he became impetuous, profane, and incapable of planning or working toward a goal. Subsequent research has implicated the frontal lobe in emotional expression, control of aggression, and the ability to work for delayed rewards. Other sites of damage have revealed additional anatomical specializations. One patient with very localized damage to the left frontal lobe of the cerebral cortex was unable to name fruits and vegetables. Describing this patient, one science writer quipped:" Does the brain have a produce section?" Similarly, damage to certain areas of the cortex on the underside of the brain results in a selective inability to recognize faces.

In the past, much of our understanding of the human mind-brain connection came from the study of victims of brain damage such as that caused by a stroke, trauma, tumor, o surgical procedure. If the victim was cooperative, and if the case came to the attention of an interested researcher, tests were administrated to define the change or loss of ability. Often, the exact extent of the damage remounted unknown until revealed by autopsy.

Now new techniques, such as the PET and MRI scans, are permitting insight into the functioning of normal, as well as diseased, brains. These and increasingly sophisticated techniques of the future will create ever-larger windows into the "black box" that is the human brain. It is possible that the exact nature of consciousness will always remain obscure, but the next decades will see continued merging of the fields of psychology and neurophysiology, and a clearer understanding of how the human brain generates the human mind.