Searching for Scary
You might not expect a neuroscientist and his lab team to take a field trip to the amusement park Astroworld. Then again, you might not expect volunteers in his experiments to be dropped from a 150-foot height in a freefall. But Baylor College of Medicine Assistant Professor David Eagleman explains that it was all part of a reality check.
“What we’re trying to figure out is how the brain represents time and one of the common anecdotal reports is that time seems to go in slow motion when people are in fear for their lives; when they are in a car accident or getting mugged or something like that. And so this is the first time that we’ve put that to the study. And we’ve actually put people in a situation that’s completely safe but extremely scary and we were able to measure whether time actually slows down for people,” says Eagleman.
“In The Matrix, for the main character, Neo, time actually slows down. He sees things in bullet time; as the bullets are coming towards him he can see it in slow motion and dodge out of the way,” Eagleman adds. “And so the question is, does that actually happen to people? Can people actually perceive the world in slow motion like that?”
Eagleman decided to do an experiment to find out.
First, the team had to find a truly frightening experience that could cause the same slow motion experience that people often report after car accidents. After Astroworld rollercoasters proved not to be scary enough, the research team settled on a freefall ride in Dallas called the Suspended Catch Air Device Diving. Despite its name, it really is more like falling than diving. The volunteers are taken up by a crane-like elevator to a 150-foot tall tower, harnessed in, dangled and then released. During the freefall they reach speeds of 70 miles per hour. Eagleman and Stetson both tried the ride themselves.
Eagleman vouches for the fear factor: “I did the plunge myself three times to make sure everything was safe and okay. And it’s absolutely terrifying. It’s so scary because you’re falling backwards and you’re going 70 miles an hour when you hit the net.”
Eagleman and first author Chess Stetson wanted to find out if slow motion experience was accompanied by an increased visual resolution. They created an LED device called a chronometer that straps on to volunteers’ wrists like a watch. The speeds of the flashing numbers can be adjusted to go slow or fast.
They found the speed at which the volunteers could no longer read the numbers and set the device to that speed. They reasoned that if the volunteers experienced slowing of time due to heightened visual perception, they would be able to read the numbers as they fell. But the volunteers could not read the numbers.
“In other words, they’re not like a video camera taking in more frames during the fall,” explains Eagleman.
Another part of the experiment required the volunteers, after falling, to estimate with a stopwatch how long their own falls took compared to those they watched other people taking. On average, the volunteers estimated that their falls took 36-percent than the duration of others’ falls.
“So there’s a paradox here,” says Eagleman. ” On one hand, they think their fall took a long time. But on the other hand, they’re not actually seeing more in time.”
Eagleman suggests in the journal PLoS One that our slow-motion experience of fearful events may be due to a trick of memory.
“Normally, your brain lays down memories though an area of the brain called the hippocampus. That’s involved in laying down memories. It turns out when something really scary is happening, the amygdala comes into play, and it lays down memories with a secondary track. So it lays down the type of memories that people have during traumatic events â€“ these so-called flashbulb memories,” explains Eagleman.
He writes in his paper, “Our findings suggest that time-slowing is a function of recollection, not perception: a richer encoding of memory may cause a salient event to appear, retrospectively, as though it lasted longer.”
Eagleman says that as scientists understand how the brain processes time, it will allow them to understand what happens when there are problems with the timing systems in the brain.
“What we’re pursuing right now is the hypothesis that schizophrenia is in fact a disorder of timing,” he says. “So, when you look at the things that characterize schizophrenia, there are credit misattributions where a schizophrenic will do something and say, ‘I wasn’t the one who did it.’ There are auditory hallucinations and we interpret that as part of the brain generating an internal voice, and part of it listening to that internal voice just like we always do, but getting the timing wrong. If you get the timing wrong that’s an auditory hallucination. So we’re engaged in experiments right now with schizophrenia patients and it appears to be the case that schizophrenia is a disorder of timing,” says Eagleman.
PUBLICATION: Public Library of Science One (PLoS One), December 11, 2007
AUTHORS: Chess Stetson, Matthew P. Fiesta & David Eagleman
RESEARCH FUNDED BY: National Institutes of Health
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