Time
Apr 19, 2011 7:48:56 GMT -5
Post by Infinite Ego on Apr 19, 2011 7:48:56 GMT -5
www.newyorker.com/reporting/2011/04/25/110425fa_fact_bilger
“I was working with Larry Mullen, Jr., on one of the U2 albums,” Eno told me. “ ‘All That You Don’t Leave Behind,’ or whatever it’s called.” Mullen was playing drums over a recording of the band and a click track—a computer-generated beat that was meant to keep all the overdubbed parts in synch. In this case, however, Mullen thought that the click track was slightly off: it was a fraction of a beat behind the rest of the band. “I said, ‘No, that can’t be so, Larry,’ ” Eno recalled. “ ‘We’ve all worked to that track, so it must be right.’ But he said, ‘Sorry, I just can’t play to it.’ ”
Eno eventually adjusted the click to Mullen’s satisfaction, but he was just humoring him. It was only later, after the drummer had left, that Eno checked the original track again and realized that Mullen was right: the click was off by six milliseconds. “The thing is,” Eno told me, “when we were adjusting it I once had it two milliseconds to the wrong side of the beat, and he said, ‘No, you’ve got to come back a bit.’ Which I think is absolutely staggering.”
Eagleman’s results later showed a “huge statistical difference,” as he put it, between the drummers’ timing and that of the random control subjects he’d tested back in Houston. When asked to keep a steady beat, for instance, the controls wavered by an average of thirty-five milliseconds; the best drummer was off by less than ten. Eno was right: drummers do have different brains from the rest. “They kicked ass over the controls,” Eagleman said. His next task would be to use the EEG data to locate the most active areas of the drummers’ brains, then target them with bursts of magnetic stimulation to see if he could disrupt their timing. “Now that we know that there is something anatomically different about them,....”
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.
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.
...“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?
The reason that a hundred-metre dash starts with a pistol shot rather than a burst of light, Eagleman pointed out, is that the body reacts much more quickly to sound. Our ears and auditory cortex can process a signal forty milliseconds faster than our eyes and visual cortex—more than making up for the speed of light.
“Imagine that there’s an accident on the highway up ahead,” he began. “One of these cars runs into that bridge.” If the crash were to occur a hundred yards away, we’d see the car hit the bridge in silence. The sound, like a peal of thunder, would take a moment to reach us. The closer the impact, the shorter the delay, but only up to a point: at a hundred and ten feet, sight and sound would suddenly lock together. Under that threshold, Eagleman explained, the signals reach the brain within a hundred milliseconds of one another, and any differences in processing are erased. In the early days of television, Eagleman told me, broadcasters noticed a similar phenomenon. Their engineers went to a great deal of trouble to synchronize sound and image, but it soon became clear that perfectionism was pointless. As long as the delay was less than a hundred milliseconds, no one noticed it...
“We’re stuck in time like fish in water,” Eagleman said, oblivious of its currents until a bubble floats by. It’s usually best that way. He had spent the past ten years peering at the world through such gaps in our perception, he said. “But sometimes you get so far down deep into reality that you want to pull back. Sometimes, in a great while, I’ll think, What if I find out that this is all an illusion?” He felt this most keenly with his schizophrenic subjects, who tended to do poorly on timing tests. The voices in their heads, he suspected, were no different from anyone else’s internal monologues; their brains just processed them a little out of sequence, so that the thoughts seemed to belong to someone else. “All it takes is this tiny tweak in the brain, this tiny change in perception,” he said, “and what you see as real isn’t real to anyone else.”