![]() ![]() “Sensory gating, the process by which the brain filters out repeated stimuli, is a problem with schizophrenia,” she says. “The diminished energy of the repeated image is just a lesser example of this.” Time Travel as Medicineĭeana Davalos, a psychologist at Colorado State University who works on timing and mental illness, agrees. “In a perfect system, the brain would know what was coming next and use zero energy to represent it,” Eagleman says. “But for this experiment, it was the Rosetta stone.” Eagleman proposed that instead of slowing down time in response to a novel flower, as Tse believes, the brain speeds it up during the repetition of the coffee cup-it recognizes the cup immediately and spends less time and energy inspecting it. “It’s a boring rule of thumb called repetition suppression,” he says. In trying to puzzle out why, Eagleman read studies reporting diminished electrical activity in the brain when it viewed a familiar image. But people found the gun-toting man no more novel than a flower. If attention is responsible for this effect, a more emotionally stirring “oddball”-like a guy pointing a gun at you, which tests have shown is much more salient than a flower-should seem to stay on the screen even longer. (Tse contends that the retina can’t process images fast enough for this to work under any circumstance Eagleman counters that studies show that the retina processes images 100 times per second, well within the range required to read his chronometer.) So Eagleman reran Tse’s oddball experiment with a twist. If this were true, then Eagleman’s jumpers should have seen the numbers on the chronometer flashing at a slower rate-and they would need to flash only a hair slower to be readable-while falling. If you’re made aware of what would normally be four seconds’ worth of data, then you think your fall lasts for four seconds. Like with the fast-acting lightbulb, your brain is stuck in the old pattern. When faced with a life-threatening situation, like falling 150 feet, your brain is presented with more information per second than it is accustomed to, so it recalibrates on the fly. “When we are paying attention,” Tse says, “the brain processes more information per second.” It’s a survival tactic. Moving shadows in the jungle could mean dinner or it could mean becoming dinner-either way, it pays to pay attention. Evolution trained our brain to notice novelty. Dartmouth College neuroscientist and time researcher Peter Tse offered another explanation. The fall doesn’t seem to take longer while you’re falling you just remember it that way. At first Eagleman was disappointed, but then he realized that the results indicated that time dilation is, in fact, a misremembered experience. Their brains didn’t actually perceive time at a slower rate. Every subject felt as if the experience lasted longer than it really did-the average estimate was closer to 4 seconds than the actual 2.6-but they could read the chronometer no better while falling than they had with two feet on the ground. “Another null effect.” In the initial round of testing, he ran 23 subjects through the high dive (one was excluded because she shut her eyes on the way down). I hit the net harder than I had prepared myself for, but I’m intact, and I sheepishly report my experience to Eagleman. That’s when he decided that dropping people off a tower could be the way to figure all this out. Eagleman remembered falling off a roof as a kid and how time seemed to stretch out forever in what was really only an instant. But they first need to know if the system is truly capable of varying the rate at which it interprets the data. Because of this, most scientists in the field have moved on to solving how parts of the brain work together to produce a single representation of time. Similar tests backed up his results, indicating that-unlike speech, which is processed in Broca’s area, or vision, which the occipital lobe handles-our sense of time is not centralized. This suggested that the brain maintains at least two separate versions of time, a master clock that feeds you a perception of the now, and another that is constantly at work tidying up that perception. He found that when people experience the time delays, there is a boost of activity in the anterior cingulate cortex, which activates only when different parts of the brain process conflicting information. ![]() Eagleman had dozens of people play 9 Square while he scanned their brains with a functional-MRI machine.
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