Michael Gazzaniga: Split brains and other heady talesMichael Gazzaniga: Split brains and other heady tales
All In The Mind
One of the big names of the brain is Michael Gazzaniga, whose career was forged in the lab of Nobel laureate Roger Sperry. His striking experiments continue to uncover the differences between your left and right hemispheres. Today he's on the US President's Bioethics Council, heads up a major project on neuroscience and the law, and is a prolific writer of popular neuroscience. He joins Natasha Mitchell to reflect on the brain's left and right, and the mysterious nature of free will.
30:14•21 Jun 2008
Split Brains, Free Will and Addiction: Michael Gazzaniga Gets Inside Our Heads
Episode Overview
- Split-brain research shows that the left and right hemispheres can operate as separate conscious systems with different strengths.
- The left hemisphere functions as an interpreter, creating explanations for behaviour even when it lacks full information.
- Conscious experience likely arises from many local brain circuits working together rather than a single global centre.
- Personal responsibility is framed as a social construct between people, not a property of brain tissue alone.
- Neuroscience is still early-stage for courtroom use, and brain scans should be treated cautiously in questions of culpability and punishment.
“We're all dualists. We immediately convert the biological reality of ourselves to personhood, to the fact that we're talking to people, not brains.”
Understand the complexities of addiction with insights from a leading brain scientist as Michael Gazzaniga sits down with host Natasha Mitchell on All In The Mind. The focus here isn’t self-help tips, but how the brain itself shapes consciousness, choice and, ultimately, the way society handles crime, addiction and responsibility.
You’ll hear Gazzaniga revisit the "heady days" in Roger Sperry’s lab, where striking split-brain experiments with patients like WJ showed that the left and right hemispheres can operate as separate conscious systems. One of his most jaw-dropping findings is that a simple surgical cut can create "two conscious systems" in one head, with the left hemisphere acting as the brain’s interpreter, constantly explaining behaviour even when it doesn’t have all the facts.
The conversation digs into what it means to say we have a mind at all. Gazzaniga argues that consciousness isn’t one grand spotlight but more like a pipe organ: countless local brain circuits each contributing their note to the overall experience. That idea underpins his view of free will and personal responsibility. As he puts it, "People are free and therefore responsible for their actions.
Brains are not responsible," stressing that responsibility lives in social rules between people, rather than in bits of neural tissue. For anyone interested in addiction and justice, the episode also touches on the huge proportion of American crime that’s drug-related, the use of brain scans in court, and why Gazzaniga thinks neuroscience is still a "baby science" that should tread carefully in legal settings.
He’s wary of overusing brain imaging to excuse behaviour, yet deeply concerned about mass incarceration, psychopathy and the way prisons have become de facto psychiatric institutions. If you’re curious about how brain science might reshape ideas of blame, choice and addiction, this conversation gives you plenty to chew on. How does thinking about "brains, not people" change the way you view responsibility?
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