How The Brain Perceives Time, with David Eagleman

Neil deGrasse Tyson and co-hosts interview Stanford neuroscientist David Eagleman about how the brain constructs perception, with a focus on time, sensory substitution, and memory. Eagleman describes work on ‘sensory substitution’—routing information through different channels—citing early experiments that mapped camera input to tactile stimulation and his own lab’s efforts to convert sound into vibration patterns on skin for deaf users.

A large portion of the episode centres on neuroplastic competition between sensory systems. Eagleman argues that unused brain ‘territory’ can be repurposed, pointing to evidence that occipital (visual) cortex can become engaged in Braille reading in blind people, and discussing echolocation in blind navigation. He then advances a hypothesis that dreaming functions as a defence of the visual cortex during sleep, claiming rapid sensory takeover can begin after about an hour of blindfolding and saying his team observed more dreaming in primate species with greater plasticity.

On time perception, Eagleman recounts an experiment dropping volunteers from a tall tower to test whether fear produces true slow-motion perception; he says the effect is instead a memory-density illusion. He also describes timing recalibration experiments where gradual delays between action and outcome can make people later experience the outcome as occurring before their action.

Eagleman links these timing effects to mental health, arguing schizophrenia may involve disrupted timing that drives misattribution of agency and auditory hallucinations, and says he is exploring a video-game-like recalibration approach. The conversation closes with a discussion of consciousness as an unsolved problem and how AI raises practical questions about detecting machine consciousness.

• Eagleman describes sensory substitution research, including converting sound into skin vibrations for deaf users.
• He says the brain can repurpose ‘visual’ cortex for non-visual tasks in blindness, including Braille-related processing.
• He argues dreams may act as ‘defensive activation’ to keep the visual cortex from being taken over during sleep.
• He says his ‘fear time-slowing’ experiment found perception does not slow; the effect comes from dense memory encoding.
• He describes timing-recalibration experiments where action–effect order can feel reversed after adaptation.
• He claims schizophrenia may fundamentally involve timing errors leading to misattributed agency and voices.
• He says consciousness remains unexplained and AI makes the question more urgent in practical terms.