Adam Weiss (W): Welcome to Simply Science from Nature Education. I’m Adam Weiss and I’m here at Harvard Medical School in Boston with Doctor Margaret Livingstone who looks how people see and looks how artists actually understand how people see. Sometimes, as well as, you guys do that, right? We are going to talk about the Mona Lisa, as an example of how artists can, they do experiments how we see.
Dr. Livingstone (L): Absolutely! So, the Mona Lisa is a very famous painting, very popular painting. And the art historians tell us it’s popular because her smile is ambiguous. You can’t tell she’s happy or said. But, if you look at the Mona Lisa, and, I want you to try looking between her eyes and mouth. So first, look at her eyes, but think about what her mouth looks like. Now, it’s kind of hard to know where your eyes are going. But try it to look at her eyes and think about how much she’s smiling.
W: So, I’m staring her right the eyes at the moment (L: Yes!) and try to think about her mouth.
L: And then look directly at her mouth.
W: It’s ambiguous.
L: Yeah, now look at her eyes again. Go back and forth and see if her expression changes.
W: It looks like she’s smiling when I look at her eyes and she’s just sitting there when I look her mouth.
L: So now, that’s not true imagination, that’s not like the art historian said. That has something to do with the way you see, not the way you think.
W: So that’s my eyes and my brain doing that to me, not my imagination.
L: It’s your eyes.
W: Really?
L: Yeah, because your vision, because the way you recognize and organize. It’s much higher acuity in your central gaze, so if you look at that central dot, all the letters in the image are equally readable. So you can see that there’s a dramatic fall off in acuity away from your central gaze.
W: Yeah, if I look at one of the big letters, I can’t see small ones at all.
L: And, so that’s why you move eyes when you read. Because the letters are tiny in the book and you could only see them in your central gaze. So, that doesn’t mean your peripheral vision is bad. It just means that your peripheral vision is designed to see bigger, blurrier things and your central vision is for looking at tiny, detailed things. But this difference in acuity with eccentricity is probably why Mona Lisa’s expression changes as you look at it. Because if you filter the Mona Lisa, in such a way that you can see what she would look at if you saw the whole thing with your peripheral vision compared to what she would look like if you saw the whole thing with your central vision which you of course can’t do. You can see that her expressions are quite different.
W: So, here we got on the left, the overall blurred version that you’ll get if you’re just in the sight of your eyes.
L: Peripheral vision, yeah.
W: And, the other side is the sharpened, just details part.
L: Yap, exactly.
W: And she’s definitely smiling while the not the other.
L: Yeah.
W: So, that’s amazing.
L: so, as you move your eyes around, her expression changes because you go from your peripheral vision to central vision in different part of image. And that gives the dynamic quality to a steady image which before the days of the video was very special thing be able to do.
W: So did and she was about this.
L: I don’t know if we aren’t all actually understood this phenomenon. Because he wrote a lot of techniques to use. He was actually a scientist. He wrote about a lot of techniques about shading and how your two eyes work and things like that, but he never wrote about this particular phenomenon. And we know that he liked this painting because he worked on it for years and then he carried it around with him for a long time till he gave it to the king of France. So he may had experienced the same thing and maybe he didn’t understand exactly what was going on.
W: Well, these are computer technology and the understanding the brain that we have these days. We can figure out but maybe he didn't know certainly very well.
L: Yes, it’s the understanding of eyes and our brain. This happens very early in the visual system, this difference between central and peripheral vision. It happens in record.
W: Uh, so, this is how we see demonstrated by da Vinci.
This 3D simulation shows a galaxy similar to Milky Way might be look 10 billion years ago. The young galaxy is experiencing a turbulent growth spurt. Cold, dense gas showed in red collapse in a heap of the galactic disk. Meanwhile, new stars are formed from the core of galaxy, driving a hot stream of gas showed in blue at temperature more than one million degrees. The interplay process makes a complex and dynamic environment.
Script: (No guarantee of accuracy.) Tentacled snake, name for the two appendages perched on the tip of its nose, is a master of ambush. But this snake has caught something other than fish lately. It’s caught the eyes of scientists. Its markable strategy for catching prey has become a subject to study. In the wild, the snake lives in the rivers in Southeast Asia. It camouflages itself by holding a pose that resembles a dead tree branch. As an unsuspecting fish swims nearby, the snake swings into action and swallow it whole. It happened so quickly that it is impossible to capture with regular film. But when view at 2000 frames per second, about a hundred times the speed of standard film. The snake’s strategy becomes clear. It uses a quick flick of its body to start on the fish, corralling it toward its head and into its mouth. The snake exploits reflex that normally helps fish it captures. Two large nerves on either sides of the body called Mauthner Neuron react pressure ways and involuntarily cause the fish to move in the opposite direction. Most of the time, this mechanism works in the fishes’ favor. But the Tentacled snake creates false waves, causing the fish to the wrong direction and straight into its waiting jaws. What about those unusual tentacles that give the snake its name? Those are actually highly-involved motion detectors perfectly tuned to the movement of fish. They let the snake detect food even in murky, silty water, its natural environment. They are features that strike fear and sometimes fangs into heart of fish everywhere. To learn more about the Tentacled snake, read the article “Natural-Born Killer” in the April issue of Scientific American.
