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MICHELE NORRIS, host:

This is ALL THINGS CONSIDERED from NPR News. I'm Michele Norris.

This next story will be of special interest to those of you who are very short, very tall or have very sensitive toes. Assuming we have your attention now, here's our science correspondent Robert Krulwich. He suggests you follow his instructions very carefully.

ROBERT KRULWICH: Okay, here is what I want you do if you are not driving: Put your hand over your left eye, and then when you're ready, switch and put your hand over your right eye and you will notice a very slight shift in what you see. Your left eye gives you one version of the world, your right eye a slightly different version. And then your brain, says neuroscientist David Eagleman...

Dr. DAVID EAGLEMAN (Neuroscientist): Stitches it all together, and then it serves up a story to you.

KRULWICH: That combines two different views into a coherent whole.

Dr. EAGLEMAN: Yeah, so the fact that the whole kit and kaboodle seems simultaneous exposes the fact that your brain is doing a lot of editing work.

KRULWICH: Your brain not only combines what your two eyes see, it combines what your two ears hear, different tastes on your tongue, and so on. Its job is to make sense of all the signals that come into your body. But here is Dr. Eagleman's startling proposition: Because it takes your brain a little time to pull all this data together, it may be that different people could have different senses of time. So, to explain this, let me do a little experiment.

I want you to imagine lying on a table, and Dr. Eagleman is going to poke in two places at the exact same moment. Now, how you do that, I'm not...

Dr. EAGLEMAN: Oh, the way you actually run the experiment is we typically computerize these things. So you would have, let's say, two - well, you have little touchers.

KRULWICH: And when he says go, those touchers touch you, let's say, on the tip of your nose and on the tip of your toe at the exact same time.

Dr. EAGLEMAN: But here's the mystery. If I were to touch your nose and your toe at the same time, the information from your nose gets to your brain essentially right away, and the information from your toe has to climb all the way up your spinal cord to get to your brain.

KRULWICH: Right? Because think about this: The distance between your nose and your brain is so short. Go ahead, touch your nose...

(Soundbite of sound effect)

KRULWICH: ...and your brain knows.

But if you touch your toe, the signal travels up your foot, then your calf, then your thigh, then your spine to your brain. So the toe signal - slower.

Dr. EAGLEMAN: And it arrives much later.

KRULWICH: Well, what do you mean by much later? I mean...

Dr. EAGLEMAN: About a tenth of a second.

KRULWICH: Oh, that much later?

Dr. EAGLEMAN: Yeah, which to the brain is a really long time. You can distinguish a tenth of a second easily. But here's the mystery. If I touch your nose and your toe at the same time, you will feel them as simultaneous. Now, how could this possibly be?

KRULWICH: How come two signals arriving at discernibly different times can feel simultaneous?

Dr. EAGLEMAN: So we figured out the way that the system actually does this. It's a very clever method.

KRULWICH: What happens, says Dr. Eagleman, is your brain puts the first signal to arrive, the nose signal, on hold, and then waits for the slower signal. And it's only when the toe signal arrives in your brain, that...

Dr. EAGLEMAN: ...you say, oh, the moment now just occurred.

KRULWICH: But in truth, the real moment now was actually a fraction of a second earlier.

Dr. EAGLEMAN: Yes.

KRULWICH: So everything you do is a little bit ago.

Dr. EAGLEMAN: Precisely. We're living in the past. You're walking around with a slight delay...

KRULWICH: Now, wait a second. Wouldn't that suggest - now, this may sound a little ridiculous - that a very tall person, let's make it a six-foot-seven person whose toe is a foot further from his brain than my toe is from my brain, wouldn't a tall person have a slightly later now than, say a short person?

Dr. EAGLEMAN: So we're testing this right now. The...

KRULWICH: Really?

Dr. EAGLEMAN: Yeah. Because if you're really tall, then you have to wait longer.

KRULWICH: For a signal to travel up from your toe.

Dr. EAGLEMAN: That's exactly the hypothesis. Yep.

(Soundbite of laughter)

KRULWICH: So, wait. Does this mean that, for a basketball star - let's say Kareem Abdul-Jabbar, who is seven feet, two inches tall. Is his now later than my now?

Dr. EAGLEMAN: Yeah, that's right. When Kareem Abdul-Jabbar thinks that now occurs, it's happened longer ago for him.

KRULWICH: Than it does for me. But when you think about it, though, the guy has such amazing reaction time. I mean, I can't dunk like him. I can't shoot...

Dr. EAGLEMAN: Wait. Good point. So let me mention something else, which is everything that we're talking about here has to do with conscious awareness of time.

KRULWICH: Dr. Eagleman says a really fine basketball player has practiced so much, his reactions have become more or less automatic and much faster than his conscious awareness. So his brain, it doesn't wait for every last bit of information to arrive and think, well, now what do I do? He just does it. But for the things that we are aware of, certainly touch, tall people and short people may have different nows.

Dr. EAGLEMAN: Yes, yes.

KRULWICH: But this is great news for short people.

Dr. EAGLEMAN: Yes.

KRULWICH: Because like, if Randy Newman writes this song, short people have no reason to live - I don't know if you know his anthem for short people.

(Soundbite of song, "Short People")

Mr. RANDY NEWMAN (Singer, Songwriter): (Singing) Short people got no reason to live.

KRULWICH: This means that short people actually live closer to the real than tall people.

Dr. EAGLEMAN: That's right. I mean, that...

(Soundbite of laughter)

Dr. EAGLEMAN: Yes, that's right. I'm not sure what good it does them.

(Soundbite of laughter)

KRULWICH: Well, David Eagleman's laboratory at Baylor College of Medicine is investigating how we perceive time in all kinds of ways. He has found time diseases, time illusions. His experiments are getting a lot of attention, but this hypothesis, this one - this one has deep appeal. Let's suppose that you're listening to the radio right now, and you are five-foot-three, and you're sitting next to someone who's six-foot-five. Do you - can you turn to the taller person and say, hey, I know about stuff a teeny bit ahead of you? Hurray!

(Soundbite of laughter)

Dr. EAGLEMAN: I think everybody should do that, yes. Turn to your taller neighbors and rub it in.

KRULWICH: Although, maybe, short people, you want to be a little careful about that.

Robert Krulwich, NPR News.

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