Monday, February 16, 2009

Re-visiting what happens during life-threatening situations

David Eagleman is guest blogging this week.

One interesting direction of transhumanism lies in the possibility of teasing out latent talents buried within us. In its grandest form, the question becomes: what are the possibilities for unearthing some sort of “superpowers”? The detection of exceptional abilities would not only (potentially) improve the human condition, but also give us stunning new data to draw from for our biological theories.

The search for hidden powers is by no means new, of course. Artists have long used drugs to enhance creativity, and students around the globe are pounding energy drinks to optimize their cognitive abilities.

But my interest, in particular, is in time perception, and so my next three posts will be about issues I’m chewing on in that domain. As George covered earlier, a few years ago I set out to address our capacity to perceive the world in slow motion. We have all experienced (or heard described) that time seems to “slow down” during a car accident, or during other high-adrenaline situations. So my laboratory performed experiments to directly address this, and, to my slight disappointment, we could find no evidence that people could really see in slow motion. Instead, they all seemed to believe that a scary event lasted longer—but only when they were reconstructing the event retrospectively. This suggested that the duration expansion during fear was a trick of memory. During a frightening event the emergency control centers in your brain quickly come online and lay down memories on a secondary memory track. Under normal circumstances, your memory is quite leaky; in frightening situations, memories tend to stick better. The end result is that we are not actually able to see in slow motion like Neo in The Matrix, but instead that consciousness seems to be postdictive, that is, constructed in retrospect. So much for the seeing-in-bullet-time superpower. Bummer.

However, since the publication of that study, I have received dozens of emails from people describing their life-threatening experiences. Despite our negative results in the slow-mo domain, there are clearly interesting things going on in the moment of an accident. I’ve noticed a few patterns. First, it seems that the duration dilation is reported only when someone sees the event approaching, as in sliding on the ice toward a truck. When a person is blindsided, there seems to be something like a loss of time: everything is over before you know what happened. So the duration dilation seems to require anticipation. This is consistent with the need for the emergency control centers to kick into gear.

The second thread in virtually all the descriptions is a total calmness about the life-threatening event as it takes place. As a historical example, in 1843, the African explorer David Livingstone was sprung upon by a lion. The lion shook Livingstone in his jaws the way a dog shakes prey. When someone else raised a rifle, the lion dropped Livingstone and went after him instead. As a result of the event, Livingstone lost power in his left arm for the rest of his life. But the extraordinary thing was that Livingstone reported that he had felt “no sense of pain nor feeling of terror, though quite conscious of what was happening.” Similarly, it is commonplace for a soldier to not notice wounds, even mortal wounds, until after the battle is over. This appears to be the result of what’s known as “stress-induced analgesia.” All the body’s resources are marshaled for fighting (or running) one’s way out of a situation, not for tending to wounds. This analgesia depends on the release of chemicals in the brain called endorphins. So that’s good news for humans who end up in bad situations. As Livingstone interpreted it, it is “a merciful provision by our benevolent Creator for lessening the pain of death.”

What’s a bit stranger, and unaddressed in the literature, is that this calmness is often accompanied by a bizarreness of thought. For example, one man reported that while he was sliding along the asphalt after being thrown from his motorcycle, he composed a little song to the tune of his helmeted head bouncing against the asphalt. No fear, no panic, just a calm little tune. And I experienced something similar when I was younger and fell from a roof. As I plummeted toward what was likely to be my death, I was calmly thinking how similar the fall was to Alice’s fall down the rabbit hole in Alice in Wonderland. No fear, no panic, just a crystal clear thought about a moment from a children’s book.

The final commonality is that people claim to have made very good decisions, especially as regards motor actions—as in “I decided to jump onto the approaching car hood,” or “I darted out of the way with no hesitation.” Of course, there is no way to assess the subjective impressions of those who made the wrong decisions, because they can’t tell us; this leaves open the possibility that the survivors who write to me are those who enjoyed a bit of luck, and their brains retrospectively construct a good story about the potency of their decision-making.

At this stage, there’s one more thing I want to look into, if I can figure out a way to do it scientifically. I’d like to better understand the common claim that “my life flashed before my eyes.” Does this really happen? It is difficult to know, at first blush, whether the statement is metaphorical. At least in some cases, the statement becomes something people say when they are trying to be clear that an event was extremely frightening. It becomes a linguistic equivalent of “that was really scary”, in the same way that saying “I was on cloud nine” is not meant to really imply something about levitation or cumulonimbi. The question is whether it is being used metaphorically in some cases, or in all cases. Take this example from another motorcycle accident victim:
…it was at this stage that I started to think of some of the people I had gone to school with in both Primary and Secondary School. I thought of the names of teachers and students that I hadn’t thought of or remembered in years and could see their faces and the school yards as vividly as if it were only a few days ago. I could hear their voices in my head and was saying their names out loud.
The challenge for brain researchers is to understand whether there is a nugget of something real at the heart of these claims, something that would force a change of our views about the capacity of memory, the potential speed of running through recall, and the power of calcified memories to suddenly shoot up to consciousness. Not surprisingly, these questions have not been addressed because of the difficulty in setting up a safe and meaningful experiment. Are there any ideas about what’s happening in these situations, or how to address these in an experiment? I’ll be very interested to hear readers post their own experiences or hypotheses.

In my next two posts I’ll address some different aspects of slow motion and the speed of perception…

David Eagleman is a neuroscientist and a writer. His book of literary fiction, Sum, debuted internationally this month.

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