You've seen it in movies so many times, it seems like just a cliche: As disaster strikes, everything seems to slow down, the seconds tick by on the clock and you experience Matrix-like awareness and reflexes.

But after experiencing the phenomenon first hand as a child by falling through a tar paper roof, Baylor College of Medicine neuroscientist David Eagleman wanted to discover how it works — does time seem to slow because your heart races and your brain thereby functions at a faster rate?

He discussed his experiment and unexpected findings on NPR's Morning Edition. (Check out the audio below.)

To scare participants enough to trigger the time warp, Eagleman first tried Astroworld rollercoasters — too tame. Then he heard about SCAD (Suspended Catch Air Device) diving — a new experience for adrenaline junkies where divers are hoisted 150 feet in the air and while facing the sky, dropped in a 100-foot freefall into an elevated net. Scary enough? No doubt. For those who don't want to use the audio, the sound of someone participating goes like this: "Aaaaaaaagggghhhhhhhhhh!!!!!!"

To bring in the science, Eagleman gave participants in Dallas (the sport is illegal in Houston) a watch-like device which flashed a series of numbers too fast to see under normal condition, under the theory that if time slows relative to human function, the numbers will slow down and be legible.

"Turns out, when you're falling you don't actually see in slow motion," says Eagleman. "It's not equivalent to the way a slow-motion camera would work — it's something more interesting than that."

Time doesn't actually slow down — just our perception of it. Participants couldn't read the watch numbers, but when asked afterwards about the 3-second fall, all guessed it took much longer.

Eagleton says the effect comes not from our heart racing but because of our memory. Programmed to remember (and thus avoid) threats, when afraid for your life the memory function clicks into overdrive, remembering stimuli and details that would normally be forgotten. As a result, when looking back at all the information processed, a short event — like a 3-second fall — seems much longer.

No word yet on why time flies when you're having fun or why a watched pot never boils.

Listen to Eagleman discuss his time-slowing experiment:

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