David Eagleman is an adjunct professor at Stanford University and the narrator of the book. He acts as a guide to complex neuroscientific concepts, translating academic research into accessible language for the general public. He advocates for using brain science to inform social policy, particularly within the criminal justice system, and promotes evidence-based rehabilitation over punishment.

Charles Whitman is a former Marine who commits a devastating mass shooting after experiencing overwhelming, irrational violent urges. An autopsy reveals a brain tumor pressing on his amygdala. This physical abnormality raises major questions about biological determinism and free will. His actions serve as a focal point for discussions on criminal culpability and neurolaw.

Mike May loses his sight at age three in a chemical explosion and opts for restorative surgery 40 years later. Despite having functional eyes post-surgery, his brain struggles to interpret the new visual data. His experience shows the active, learned nature of visual perception.

Ian Waterman suffers from a rare neurological illness that destroys his innate body awareness. He must consciously direct every physical movement with intense visual focus, risking a fall if his concentration lapses. His daily routine demonstrates the massive computational power of the unconscious brain.

Jan Scheuermann is paralyzed from the neck down by a degenerative genetic disorder. She participates in a study utilizing electrodes implanted in her motor cortex, successfully learning to control a sophisticated robotic arm with her thoughts. She represents the potential of neuroplasticity in a new bionic era.

Sigmund Freud is the foundational Austrian psychologist who developed psychoanalysis. He serves as an intellectual predecessor to modern neuroscience by insisting that behavior stems from physical processes rather than abstract philosophy. His early theories anticipate modern findings regarding the power of the unconscious.

Austin Naber is a 10-year-old cup-stacking champion whose highly automated skills are measured against a novice. His brain activity remains calm and energy-efficient during his rapid routine, demonstrating the concept of procedural memory.

Ken Parks carries out complex, goal-directed violence entirely without conscious involvement. He is later acquitted. His case provides an extreme example of the unconscious brain's capabilities and challenges legal definitions of intent.

Tammy Myers is a former engineer whose orbitofrontal cortex is damaged in a motorcycle crash. Because she can no longer integrate emotional and bodily signals, she suffers from severe indecision despite retaining her rational faculties.

John Robison has Asperger's syndrome and undergoes transcranial magnetic stimulation. Following the procedure, he gains the ability to perceive emotional information in facial expressions, showing the physical basis of social understanding.

Dr. Alvaro Pascual-Leone is a medical researcher who conducts transcranial magnetic stimulation experiments. His work helps individuals with atypical neurological conditions access new channels of social communication.

Sarah Shourd is a journalist whose extended isolation causes severe psychological distress. Her experience provides real-world context for clinical data on social exclusion, proving that the brain processes isolation as physical pain.

Jane Elliott is an Iowa schoolteacher who arbitrarily divides her class by eye color to teach them about prejudice. Her exercise forces students to experience systemic bias firsthand. This practice demonstrates education's role in cultivating empathy.

Cameron Mott is a young epilepsy patient who has half of her brain surgically removed. The remaining half successfully rewires itself to assume nearly all lost functions. This recovery provides a clear example of extreme brain plasticity.

Dr. Charles Nelson is a professor at Boston Children's Hospital who studies the cognitive and emotional deficits of children raised in deprived state-run facilities. His research proves that a nurturing environment is essential for normal brain development.

Professor Elizabeth Loftus is a psychologist at the University of California, Irvine. She demonstrates that human memory is not a factual recording but a fragile reconstruction highly susceptible to modification and falsehood.

Jeb Corliss is a wingsuit flyer whose extreme sports experiences provide data on temporal distortion. His accounts help explain how the brain records memories with much greater density during a crisis, creating the retrospective illusion of slow motion.