The mysteries of time and the brain

Why does time slow down when we fear for our lives? Does the brain shift gears for a few suspended seconds and perceive the world at half speed, or is some other mechanism at work? Time is subjective, it comes down to perception, and it's intrinsically linked to memory. Read how the surreal trippy feeling of falling off a roof as a boy sparked a quest to study "the coolest thing in the world" in this amazing article by Burkhard Bilger in The New Yorker: What a brush with death taught David Eagleman about the mysteries of time and the brain.

When David Eagleman was eight years old, he fell off a roof and kept on falling. Or so it seemed at the time. His family was living outside Albuquerque, in the foothills of the Sandia Mountains. There were only a few other houses around, scattered among the bunchgrass and the cholla cactus, and a new construction site was the Eagleman boys’ idea of a perfect playground. David and his older brother, Joel, had ridden their dirt bikes to a half-finished adobe house about a quarter of a mile away. When they’d explored the rooms below, David scrambled up a wooden ladder to the roof. He stood there for a few minutes taking in the view—west across desert and subdivision to the city rising in the distance—then walked over the newly laid tar paper to a ledge above the living room. “It looked stiff,” he told me recently. “So I stepped onto the edge of it.”

In the years since, Eagleman has collected hundreds of stories like his, and they almost all share the same quality: in life-threatening situations, time seems to slow down. He remembers the feeling clearly, he says. His body stumbles forward as the tar paper tears free at his feet. His hands stretch toward the ledge, but it’s out of reach. The brick floor floats upward—some shiny nails are scattered across it—as his body rotates weightlessly above the ground. It’s a moment of absolute calm and eerie mental acuity. But the thing he remembers best is the thought that struck him in midair: this must be how Alice felt when she was tumbling down the rabbit hole.

Eagleman is thirty-nine now and an assistant professor of neuroscience at Baylor College of Medicine, in Houston. Physically, he seems no worse for the fall. He did a belly flop on the bricks, he says, and his nose took most of the impact. “He made a one-point landing,” as his father puts it. The cartilage was so badly smashed that an emergency-room surgeon had to remove it all, leaving Eagleman with a rubbery proboscis that he could bend in any direction. But it stiffened up eventually, and it’s hard to tell that it was ever injured. Eagleman has puckish, neatly carved features, with a lantern jaw and modish sideburns. In Baylor’s lab-coated corridors, he wears designer jeans and square-toed ankle boots, and walks with a bounce in his step that’s suspiciously close to a strut, like Pinocchio heading off to Pleasure Island.

If Eagleman’s body bears no marks of his childhood accident, his mind has been deeply imprinted by it. He is a man obsessed by time. As the head of a lab at Baylor, Eagleman has spent the past decade tracing the neural and psychological circuitry of the brain’s biological clocks. He has had the good fortune to arrive in his field at the same time as fMRI scanners, which allow neuroscientists to observe the brain at work, in the act of thinking. But his best results have often come through more inventive means: video games, optical illusions, physical challenges. Eagleman has a talent for testing the untestable, for taking seemingly sophomoric notions and using them to nail down the slippery stuff of consciousness. “There are an infinite number of boring things to do in science,” he told me. “But we live these short life spans. Why not do the thing that’s the coolest thing in the world to do?”

The Eagleman lab, on the ground floor of Baylor’s Ben Taub General Hospital, could be the lair of a precocious but highly distractible teen-ager. The doors are pinned with cartoons, the counters strewn with joysticks and other gizmos. The conference table is flanked by a large red rubber ball, for use as a chair or a Hippity Hop. When Eagleman first moved in, he had the walls painted baby blue, with a shiny finish designed to be erasable. By now, they’ve been covered from floor to ceiling with equations, graphs, time lines, to-do lists, aphorisms, and sketches of brain waves—a Pollocky palimpsest of red, green, purple, and black scribblings. “The old stuff is really hard to erase,” Eagleman told me. “It’s like memory that way.”

Although Eagleman and his students study timing in the brain, their own sense of time tends to be somewhat unreliable. Eagleman wears a Russian wristwatch to work every morning, though it’s been broken for months. “The other day, I was in the lab,” he told me, “and I said to Daisy, who sits in the corner, ‘Hey, what time is it?’ And she said, ‘I don’t know. My watch is broken.’ It turns out that we’re all wearing broken watches.” Scientists are often drawn to things that bedevil them, he said. “I know one lab that studies nicotine receptors and all the scientists are smokers, and another lab that studies impulse control and they’re all overweight.” But Eagleman’s ambivalence goes deeper. Clocks offer at best a convenient fiction, he says. They imply that time ticks steadily, predictably forward, when our experience shows that it often does the opposite: it stretches and compresses, skips a beat and doubles back.

The brain is a remarkably capable chronometer for most purposes. It can track seconds, minutes, days, and weeks, set off alarms in the morning, at bedtime, on birthdays and anniversaries. Timing is so essential to our survival that it may be the most finely tuned of our senses. In lab tests, people can distinguish between sounds as little as five milliseconds apart, and our involuntary timing is even quicker. If you’re hiking through a jungle and a tiger growls in the underbrush, your brain will instantly home in on the sound by comparing when it reached each of your ears, and triangulating between the three points. The difference can be as little as nine-millionths of a second.

Yet “brain time,” as Eagleman calls it, is intrinsically subjective. “Try this exercise,” he suggests in a recent essay. “Put this book down and go look in a mirror. Now move your eyes back and forth, so that you’re looking at your left eye, then at your right eye, then at your left eye again. When your eyes shift from one position to the other, they take time to move and land on the other location. But here’s the kicker: you never see your eyes move.” There’s no evidence of any gaps in your perception—no darkened stretches like bits of blank film—yet much of what you see has been edited out. Your brain has taken a complicated scene of eyes darting back and forth and recut it as a simple one: your eyes stare straight ahead. Where did the missing moments go?

The question raises a fundamental issue of consciousness: how much of what we perceive exists outside of us and how much is a product of our minds? Time is a dimension like any other, fixed and defined down to its tiniest increments: millennia to microseconds, aeons to quartz oscillations. Yet the data rarely matches our reality. The rapid eye movements in the mirror, known as saccades, aren’t the only things that get edited out. The jittery camera shake of everyday vision is similarly smoothed over, and our memories are often radically revised. What else are we missing? When Eagleman was a boy, his favorite joke had a turtle walking into a sheriff’s office. “I’ve just been attacked by three snails!” he shouts. “Tell me what happened,” the sheriff replies. The turtle shakes his head: “I don’t know, it all happened so fast.”

A few years ago, Eagleman thought back on his fall from the roof and decided that it posed an interesting research question. Why does time slow down when we fear for our lives? Does the brain shift gears for a few suspended seconds and perceive the world at half speed, or is some other mechanism at work? The only way to know for sure was to re-create the situation in a controlled setting. Eagleman and one of his graduate students, Chess Stetson, who is now at Caltech, began by designing and programming a “perceptual chronometer.” About the size of a pack of cards, it had an L.E.D. display connected to a circuit board and powered by a nine-volt battery. The unit could be strapped to a subject’s wrist, where it would flash a number at a rate just beyond the threshold of perception. If time slowed down, Eagleman reasoned, the number would become visible. Now he just needed a good, life-threatening situation.... Read the rest of this article here (it's worth it).