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Looking At What The Eyes See

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We move our eyes three times a second, over 100,000 times each day. Why isn't life blurrier? Reporting in Nature Neuroscience, psychologist Martin Rolfs and colleagues found that our mind seems to prepare for our eye movements before they occur, helping us keep track of objects in the visual field.

IRA FLATOW, host:

Up now, Flora Lichtman is here. Hi, Flora.

FLORA LICHTMAN: Hi, Ira.

FLATOW: Video Pick of the Week. What have you got for us today?

LICHTMAN: Well, we were just talking about illusions, a big illusion, right? Well, it turns out that our eyes, our visual system, they're sort of more minor illusions all day long. So the Video Pick of the Week this week is about what our eyes see and how that's different from what we perceive.

FLATOW: What we see being different from what we perceive - a fine difference?

LICHTMAN: Right. Well - see, let me give you an example.

FLATOW: OK. Good idea.

LICHTMAN: So our eyes move over 100,000 times per day, these rapid eye movements. More than three times a second, we're moving our eyes around.

FLATOW: Wow.

LICHTMAN: In fact, if you look at someone, if you look into the person's eyes next to you...

(Soundbite of laughter)

FLATOW: I'm looking.

LICHTMAN: ...for example, you'll notice that their eyes are not staying still. And so you're moving your eyes all this time, but you notice that life is not so blurry.

FLATOW: It's not blurry. It's not like you see on TV when they pan the camera too quickly, right?

LICHTMAN: That's right. That we - our eyes are not working like a camera pan. We tune out that pan. That's one sort of illusion that we do. But Martin Rolfs is interested in another question, which is, you know, how do you keep track of things on - in your eye, when you're moving around so much?

FLATOW: Right. Right. Right.

LICHTMAN: And so one thing that he knows is that when your eye stops moving, you refresh the image on the back of the eye. And in fact, he actually -there's some news you can use in here. Martin Rolfs has this news you can use about how to tell if you're dreaming or awake.

Dr. MARTIN ROLFS (Department of Psychology, New York University): And that's actually how you can tell imagery from a real visual experience, because if you move your eyes, things change on the retina. If you move your eyes while you're imagining, while you're hallucinating, nothing changes. So if you want to know if you're dreaming or not, you should just move your eyes or your body.

(Soundbite of laughter)

LICHTMAN: Forget the pinch test. Just do the retina test.

FLATOW: Just move your eyes. Do the retina test. And so, your Video Pick of the Week, we're going to see what?

LICHTMAN: So in this, we look at Rolfs's study where he tracks our eyeballs. He puts people in front of a high-speed camera, and he has this software that will follow your eyeballs around. So that's kind of, first of all, kind of cool to see.

FLATOW: Yeah, that's cool.

(Soundbite of laughter)

LICHTMAN: And what he finds is that our attention, our eyes move all the time and it seems like our visual system is sort of prepared for this movement. Almost like our - part of our brain knows where our eyes are going to move before they move.

FLATOW: It anticipates?

LICHTMAN: It anticipates the movement.

FLATOW: And so it moves the visual field in advance of where we think we're going to be going?

LICHTMAN: Right. I mean, if you hold your finger or your thumb, in front of your eyes and you move your eyes around...

FLATOW: Right.

LICHTMAN: you notice that your thumb is going to change position in the visual field.

FLATOW: Right.

LICHTMAN: This happens all the time. So to keep your attention on your thumb, your visual system prepares for that movement in a fraction of a second before the movement happens. So you start paying attention to where your thumb is going to be after the movement takes place, before the movement happens. It's complicated.

(Soundbite of laughter)

FLATOW: But you show it very well. That's why we have visuals.

LICHTMAN: That's why we have visuals.

(Soundbite of laughter)

FLATOW: You can go to our Video Pick of the Week on our webpage at sciencefriday.com. You'll see Flora's Video Pick of the Week, where she shows exactly how your eye anticipates.

LICHTMAN: Yeah. So even I threw in a lemur because I figured there needs to be some enticing thing to get people to watch this.

FLATOW: Get a critter in there whenever we can.

LICHTMAN: Yes, exactly.

(Soundbite of laughter)

FLATOW: And so he studied this, this is what he does for a living. He studies how we look at things?

LICHTMAN: Yes. I mean, these rapid eye movements are kind of interesting. I asked if you could look into someone eyes and tell where they're paying attention, and he said there are these microsaccades, these really tiny eye movements that are sort of correlated to attention.

So if you're at a party, you're at a cocktail party, and you're trying to gauge the person's interests that you're talking to, you'd have to look very closely to tell whether they're interested. But if you see their eyes darting off all the time to the side, that's a pretty good indicator that it's not going well.

FLATOW: Yes. Much like they're darting toward their watch.

(Soundbite of laughter)

LICHTMAN: Yeah.

FLATOW: All right, Flora, thank you. Flora's Video Pick of the Week, it's up there at sciencefriday.com. It's on our website. And it's - click on the video on the left side. We'll also give you links on our webpage and our Facebook page; there'll be a link to the video. We have a Facebook page at facebook/scifri. We invite you to go there.

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