The more we learn about the human brain, the more puzzling the question of free will becomes.

Forty years ago, cognitive neuroscientist Gazzaniga (Human: The Science Behind What Makes Your Brain Unique, 2008, etc.)—the director of the SAGE Center for the Study of Mind at the University of California, Santa Barbara—pioneered the study of the different functions of the right and left hemispheres of the human brain. Since then, it has become clear that what characterizes the human brain is not simply its size—after all, Neanderthal brains were larger—or even the greater connectivity of our neurons than occurs in the brains of our chimpanzee cousins. Neuropsychologists have established that the human brain is composed of specialized modules, local circuits that each operate automatically. "The end result is thousands of modules, each doing their own thing," writes the author, so that "our conscious awareness is the mere tip of the iceberg of non-conscious processing." This capability allowed us to create culture and technology, our hallmark as a species, but we are left with a disturbing question: "[W]hy do we feel so unified and in control" if our conscious experience is the result of "positive feedback" from modules that are each acting independently in response to environmental challenges? Gazzaniga goes on to pose the deeper question of whether can exist if "the thoughts that arise from our minds are also determined," as can be shown experimentally by brain scans. If the brain is made up of subsystems without any one locus of control, can the concept of free will have any meaning? The author examines this knotty question from many different angles and offers a simple analogy to explain how, in his view, consciousness and moral responsibility emerge from social interaction. In other words, the rules of traffic are collective and cannot be reduced to the behavior of individual cars.

A fascinating affirmation of our essential humanity.