Who's in Charge? Free Will and the Science of the Brain

Michael S. Gazzaniga is one of the founders of cognitive neuroscience — he co-coined the field's name — and at the time of writing he directed the SAGE Center for the Study of the Mind at the University of California, Santa Barbara. His career was built on split-brain research: studies, beginning with Roger Sperry (whose work won the 1981 Nobel Prize) and continued with Joseph LeDoux, of patients whose corpus callosum had been severed so the two hemispheres could no longer communicate. Out of those studies came the concept this book popularises — the left-hemisphere "interpreter," the confabulation mechanism that supplies reasons for behaviour whose real cause it cannot see.

The book was published in 2011 by Ecco, a HarperCollins imprint, as a trade adaptation of Gazzaniga's 2009 Gifford Lectures. The filter between author and page is a trade editor and a general-readership market, not peer review; the underlying science is carried in his and others' primary papers, which the book synthesises. Its central demonstration is the classic split-brain experiment: the right hemisphere is shown an instruction the speaking left hemisphere cannot access — a snow scene, say — the left hand selects a matching object such as a shovel, and when the patient is asked why, the left hemisphere, with no knowledge of the real prompt, invents a plausible reason on the spot rather than answering "I don't know." Gazzaniga's argument is that this fabricating narrator is not a quirk of damaged brains but the ordinary basis of the unified self and its sense of choosing.

The book sits as a secondary, synthesising work for a popular audience, resting on a primary experimental literature that can be chased through Gazzaniga's research papers. Its interpreter is the neuroscientific sibling of the findings in Nisbett and Wilson, where people report a priori causal theories in place of introspection, and of Haidt's account of moral reasoning as post-hoc justification; the three describe the same gap between a decision and its stated reason at three different levels — hemisphere, cognition, and moral judgment. That gap is the human counterpart to the machine question of whether a model's stated reasons match its computation, which Turpin takes up directly.

Gazzaniga's stake is reputational and, in part, philosophical. The interpreter is his signature contribution, and the book uses it to argue a particular position — that responsibility survives in a determined brain because it lives at the social level rather than the neural one — so he writes as the originator of the theory and an advocate of the conclusions he draws from it. There is no commercial conflict beyond the ordinary interest of a trade author in a book that sells.