Well, that all depends on how you look at it … Ambiguous image illusions seem to simultaneously point out limitations in our visual system (dependence on shapes, edges and previous experiences in interpreting what’s in our visual field) as well as its flexibility (because in the end, most of us can see both shapes). Think about that while you explore the young lady/old lady, rabbit/duck and whale/kangaroo illusions above. I wonder how these work for people who experience “face blindness”, the inability to recognize and identify faces. Radiolab explored that condition previously.
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Well, that all depends on how you look at it … Ambiguous image illusions seem to simultaneously point out limitations in our visual system (dependence on shapes, edges and previous experiences in interpreting what’s in our visual field) as well as its flexibility (because in the end, most of us can see both shapes). Think about that while you explore the young lady/old lady, rabbit/duck and whale/kangaroo illusions above. I wonder how these work for people who experience “face blindness”, the inability to recognize and identify faces. Radiolab explored that condition previously.
Zoom Info
Well, that all depends on how you look at it … Ambiguous image illusions seem to simultaneously point out limitations in our visual system (dependence on shapes, edges and previous experiences in interpreting what’s in our visual field) as well as its flexibility (because in the end, most of us can see both shapes). Think about that while you explore the young lady/old lady, rabbit/duck and whale/kangaroo illusions above. I wonder how these work for people who experience “face blindness”, the inability to recognize and identify faces. Radiolab explored that condition previously.
Zoom Info

Well, that all depends on how you look at it …

Ambiguous image illusions seem to simultaneously point out limitations in our visual system (dependence on shapes, edges and previous experiences in interpreting what’s in our visual field) as well as its flexibility (because in the end, most of us can see both shapes).

Think about that while you explore the young lady/old lady, rabbit/duck and whale/kangaroo illusions above.

I wonder how these work for people who experience “face blindness”, the inability to recognize and identify faces. Radiolab explored that condition previously.

This GIF might break your brain a little:

Take a look at the sequence of images below (I recommend clicking through to enlarge, Tumblr Dashboard folks). Works best if you stare at the dot:

Color? Or black and white?

The rods and cones of your retina respond to the illumination (black-white) and color of a scene, respectively. But that input passes through one key information filter on the way to your visual cortex. 

In a sense, your rods and cones take a wavelength survey of the visual field, measuring all the wavelengths they are capable of measuring. It’s the “opponent process” that begins to give color meaning. It’s not only how “red” something is, it’s also how “not green” it is. Likewise, a yellow tulip in the original image from above is intensely “not blue”.

When looking at the “blue” tulips, your blue photoreceptors get fatigued. This creates the illusion of yellow when the blue surplus is taken away. 

Ouch. I need to close my eyes.

Beau Lotto: Optical illusions show how we see

One of the best TED talks I’ve seen in recent memory. Sit down and prepare to get a bit of a brain cramp as you are taken through a series of truly awesome optical illusions.

In the process, you will learn a bit about how we perceive the world. In a sense, these tricks show us how our eyes work, but more accurately it shows us how our brains make sense of all that visual information.

You begin with particular wavelengths of light, the purely physical thingness of things. You end with a perception of your surroundings, tricks and all. All the between bits are where the fun lives.

What IS an illusion???

Source: youtube.com

via explore-blog:

The human eye is one of the most powerful machines on the planet: It’s like a 5000-megapixel camera that can run in bright light, near-darkness, and even underwater.

And yet our eyes an imperfect: What a camera sees that our eyes don’t. Complement with 100 ideas that changed photography. 

Our eye is (and isn’t) like a camera, but our brain is certainly more than a roll of film. I mean, what mere roll of film could create a picture like the brush of Claude Monet, who near the end of his life could see into the ultraviolet?

the-science-llama: Animal Eye Close-Ups By Suren Manvelyan Jeepers creepers, where’d you get them peepers? Aren’t eyes just great? It’s amazing to see how evolution has solved a single problem in such a myriad of ways. Actually, to be more accurate, it’s amazing to see that evolution has molded such diverse and intricate machinery from perhaps the same starting point. That’s right. Although it’s long been thought that animal eyes evolved separately as many as 40 times, eyes most likely owe their varied existence all to one single gene. That gene is named Pax6, and it’s a master control switch for many of the things that end up becoming eyes in jellyfish, flies, snakes and even humans. It doesn’t make eyes on its own, but acts like the conductor during the symphony of development. The protein it makes looks like this: Now that we are sequencing more and more genomes, and deciphering the precise DNA sequence of Pax6 in all of those diverse creatures, we are able to map out how that gene has changed over time. Like a game of molecular telephone, DNA sequences (usually) get more and more scrambled as they spread into new species. Follow the molecular breadcrumbs back far enough, and you can find out where you came from. And for all those oodles of eyes, all gorgeous, intricate and exquisite, Pax6 might hold the key to seeing where vision began. 
Zoom Info
the-science-llama: Animal Eye Close-Ups By Suren Manvelyan Jeepers creepers, where’d you get them peepers? Aren’t eyes just great? It’s amazing to see how evolution has solved a single problem in such a myriad of ways. Actually, to be more accurate, it’s amazing to see that evolution has molded such diverse and intricate machinery from perhaps the same starting point. That’s right. Although it’s long been thought that animal eyes evolved separately as many as 40 times, eyes most likely owe their varied existence all to one single gene. That gene is named Pax6, and it’s a master control switch for many of the things that end up becoming eyes in jellyfish, flies, snakes and even humans. It doesn’t make eyes on its own, but acts like the conductor during the symphony of development. The protein it makes looks like this: Now that we are sequencing more and more genomes, and deciphering the precise DNA sequence of Pax6 in all of those diverse creatures, we are able to map out how that gene has changed over time. Like a game of molecular telephone, DNA sequences (usually) get more and more scrambled as they spread into new species. Follow the molecular breadcrumbs back far enough, and you can find out where you came from. And for all those oodles of eyes, all gorgeous, intricate and exquisite, Pax6 might hold the key to seeing where vision began. 
Zoom Info
the-science-llama: Animal Eye Close-Ups By Suren Manvelyan Jeepers creepers, where’d you get them peepers? Aren’t eyes just great? It’s amazing to see how evolution has solved a single problem in such a myriad of ways. Actually, to be more accurate, it’s amazing to see that evolution has molded such diverse and intricate machinery from perhaps the same starting point. That’s right. Although it’s long been thought that animal eyes evolved separately as many as 40 times, eyes most likely owe their varied existence all to one single gene. That gene is named Pax6, and it’s a master control switch for many of the things that end up becoming eyes in jellyfish, flies, snakes and even humans. It doesn’t make eyes on its own, but acts like the conductor during the symphony of development. The protein it makes looks like this: Now that we are sequencing more and more genomes, and deciphering the precise DNA sequence of Pax6 in all of those diverse creatures, we are able to map out how that gene has changed over time. Like a game of molecular telephone, DNA sequences (usually) get more and more scrambled as they spread into new species. Follow the molecular breadcrumbs back far enough, and you can find out where you came from. And for all those oodles of eyes, all gorgeous, intricate and exquisite, Pax6 might hold the key to seeing where vision began. 
Zoom Info
the-science-llama: Animal Eye Close-Ups By Suren Manvelyan Jeepers creepers, where’d you get them peepers? Aren’t eyes just great? It’s amazing to see how evolution has solved a single problem in such a myriad of ways. Actually, to be more accurate, it’s amazing to see that evolution has molded such diverse and intricate machinery from perhaps the same starting point. That’s right. Although it’s long been thought that animal eyes evolved separately as many as 40 times, eyes most likely owe their varied existence all to one single gene. That gene is named Pax6, and it’s a master control switch for many of the things that end up becoming eyes in jellyfish, flies, snakes and even humans. It doesn’t make eyes on its own, but acts like the conductor during the symphony of development. The protein it makes looks like this: Now that we are sequencing more and more genomes, and deciphering the precise DNA sequence of Pax6 in all of those diverse creatures, we are able to map out how that gene has changed over time. Like a game of molecular telephone, DNA sequences (usually) get more and more scrambled as they spread into new species. Follow the molecular breadcrumbs back far enough, and you can find out where you came from. And for all those oodles of eyes, all gorgeous, intricate and exquisite, Pax6 might hold the key to seeing where vision began. 
Zoom Info
the-science-llama: Animal Eye Close-Ups By Suren Manvelyan Jeepers creepers, where’d you get them peepers? Aren’t eyes just great? It’s amazing to see how evolution has solved a single problem in such a myriad of ways. Actually, to be more accurate, it’s amazing to see that evolution has molded such diverse and intricate machinery from perhaps the same starting point. That’s right. Although it’s long been thought that animal eyes evolved separately as many as 40 times, eyes most likely owe their varied existence all to one single gene. That gene is named Pax6, and it’s a master control switch for many of the things that end up becoming eyes in jellyfish, flies, snakes and even humans. It doesn’t make eyes on its own, but acts like the conductor during the symphony of development. The protein it makes looks like this: Now that we are sequencing more and more genomes, and deciphering the precise DNA sequence of Pax6 in all of those diverse creatures, we are able to map out how that gene has changed over time. Like a game of molecular telephone, DNA sequences (usually) get more and more scrambled as they spread into new species. Follow the molecular breadcrumbs back far enough, and you can find out where you came from. And for all those oodles of eyes, all gorgeous, intricate and exquisite, Pax6 might hold the key to seeing where vision began. 
Zoom Info
the-science-llama: Animal Eye Close-Ups By Suren Manvelyan Jeepers creepers, where’d you get them peepers? Aren’t eyes just great? It’s amazing to see how evolution has solved a single problem in such a myriad of ways. Actually, to be more accurate, it’s amazing to see that evolution has molded such diverse and intricate machinery from perhaps the same starting point. That’s right. Although it’s long been thought that animal eyes evolved separately as many as 40 times, eyes most likely owe their varied existence all to one single gene. That gene is named Pax6, and it’s a master control switch for many of the things that end up becoming eyes in jellyfish, flies, snakes and even humans. It doesn’t make eyes on its own, but acts like the conductor during the symphony of development. The protein it makes looks like this: Now that we are sequencing more and more genomes, and deciphering the precise DNA sequence of Pax6 in all of those diverse creatures, we are able to map out how that gene has changed over time. Like a game of molecular telephone, DNA sequences (usually) get more and more scrambled as they spread into new species. Follow the molecular breadcrumbs back far enough, and you can find out where you came from. And for all those oodles of eyes, all gorgeous, intricate and exquisite, Pax6 might hold the key to seeing where vision began. 
Zoom Info

the-science-llama:

Animal Eye Close-Ups

By Suren Manvelyan

Jeepers creepers, where’d you get them peepers?

Aren’t eyes just great? It’s amazing to see how evolution has solved a single problem in such a myriad of ways. Actually, to be more accurate, it’s amazing to see that evolution has molded such diverse and intricate machinery from perhaps the same starting point.

That’s right. Although it’s long been thought that animal eyes evolved separately as many as 40 times, eyes most likely owe their varied existence all to one single gene. That gene is named Pax6, and it’s a master control switch for many of the things that end up becoming eyes in jellyfish, flies, snakes and even humans. It doesn’t make eyes on its own, but acts like the conductor during the symphony of development. The protein it makes looks like this:

Now that we are sequencing more and more genomes, and deciphering the precise DNA sequence of Pax6 in all of those diverse creatures, we are able to map out how that gene has changed over time. Like a game of molecular telephone, DNA sequences (usually) get more and more scrambled as they spread into new species. Follow the molecular breadcrumbs back far enough, and you can find out where you came from.

And for all those oodles of eyes, all gorgeous, intricate and exquisite, Pax6 might hold the key to seeing where vision began. 

(via sagansense)

Source: surenmanvelyan.com

Seeing (Infra)Red

I’m continually amazed at the added beauty of the world when we are allowed to view it from a point beyond our usual sensory range.

Do you know why plants are green? It’s because they reflect green light more intensely than other colors. If anything, that kind of makes them not green. If it doesn’t contribute to photosynthesis, they have no use for it. And although we can’t see it with our limited vision, they also eschew the infrared. 

Andrew Shurtleff has made a stunning time-lapse showcasing the world as viewed in near-infrared. The light-sensitive chips of digital cameras can sense these wavelengths outside human vision (near-infrared being about 800-2000 nm wavelengths compared to our 400-700 nm visual range). With the right kind of video editing, that infrared world comes alive like a planet painted from pure ice. The leafy material appears white due to its intense reflection of infrared light.

Holy wow.

Infrared photography has been used for decades to study vegetation. Kodak’s infrared-sensitive Aerochrome film paints the plant world in an eerie dusting of pink that you’ll have to see to believe. And NASA, whose scientists use the entirety of the electromagnetic spectrum to paint pictures of our world and others in Pepto-pink, create amazing works of Earth as art using infrared filters:

(via Bad Astronomy)

Source: Slate

Via neuronympho: Did you know chickens ‘one-up’ humans in ability to see color?Scientists mapped five types of light receptors in the chicken’s eye. They discovered the receptors were laid out in interwoven mosaics that maximized the chicken’s ability to see many colors in any given part of the retina, the light-sensing structure at the back of the eye…. “The human retina has cones sensitive to red, blue and green wavelengths,” Corbo explains. “Avian retinas also have a cone that can detect violet wavelengths, including some ultraviolet, and a specialized receptor called a double cone that we believe helps them detect motion.” Detect motion? Wait. In Jurassic Park, the T. rex sensed motion. And chickens are like tiny, feathered dinosaurs. Colonel Sanders is our John Hammond. We are so screwed. (As a scientist, I would be remiss if I didn’t tell you that the T. rex vision claims of Jurassic Park are completely bonkers and quite wrong. Still, the chicken vision part is quite cool.)
Zoom Info
Via neuronympho: Did you know chickens ‘one-up’ humans in ability to see color?Scientists mapped five types of light receptors in the chicken’s eye. They discovered the receptors were laid out in interwoven mosaics that maximized the chicken’s ability to see many colors in any given part of the retina, the light-sensing structure at the back of the eye…. “The human retina has cones sensitive to red, blue and green wavelengths,” Corbo explains. “Avian retinas also have a cone that can detect violet wavelengths, including some ultraviolet, and a specialized receptor called a double cone that we believe helps them detect motion.” Detect motion? Wait. In Jurassic Park, the T. rex sensed motion. And chickens are like tiny, feathered dinosaurs. Colonel Sanders is our John Hammond. We are so screwed. (As a scientist, I would be remiss if I didn’t tell you that the T. rex vision claims of Jurassic Park are completely bonkers and quite wrong. Still, the chicken vision part is quite cool.)
Zoom Info
Via neuronympho: Did you know chickens ‘one-up’ humans in ability to see color?Scientists mapped five types of light receptors in the chicken’s eye. They discovered the receptors were laid out in interwoven mosaics that maximized the chicken’s ability to see many colors in any given part of the retina, the light-sensing structure at the back of the eye…. “The human retina has cones sensitive to red, blue and green wavelengths,” Corbo explains. “Avian retinas also have a cone that can detect violet wavelengths, including some ultraviolet, and a specialized receptor called a double cone that we believe helps them detect motion.” Detect motion? Wait. In Jurassic Park, the T. rex sensed motion. And chickens are like tiny, feathered dinosaurs. Colonel Sanders is our John Hammond. We are so screwed. (As a scientist, I would be remiss if I didn’t tell you that the T. rex vision claims of Jurassic Park are completely bonkers and quite wrong. Still, the chicken vision part is quite cool.)
Zoom Info
Via neuronympho: Did you know chickens ‘one-up’ humans in ability to see color?Scientists mapped five types of light receptors in the chicken’s eye. They discovered the receptors were laid out in interwoven mosaics that maximized the chicken’s ability to see many colors in any given part of the retina, the light-sensing structure at the back of the eye…. “The human retina has cones sensitive to red, blue and green wavelengths,” Corbo explains. “Avian retinas also have a cone that can detect violet wavelengths, including some ultraviolet, and a specialized receptor called a double cone that we believe helps them detect motion.” Detect motion? Wait. In Jurassic Park, the T. rex sensed motion. And chickens are like tiny, feathered dinosaurs. Colonel Sanders is our John Hammond. We are so screwed. (As a scientist, I would be remiss if I didn’t tell you that the T. rex vision claims of Jurassic Park are completely bonkers and quite wrong. Still, the chicken vision part is quite cool.)
Zoom Info
Via neuronympho: Did you know chickens ‘one-up’ humans in ability to see color?Scientists mapped five types of light receptors in the chicken’s eye. They discovered the receptors were laid out in interwoven mosaics that maximized the chicken’s ability to see many colors in any given part of the retina, the light-sensing structure at the back of the eye…. “The human retina has cones sensitive to red, blue and green wavelengths,” Corbo explains. “Avian retinas also have a cone that can detect violet wavelengths, including some ultraviolet, and a specialized receptor called a double cone that we believe helps them detect motion.” Detect motion? Wait. In Jurassic Park, the T. rex sensed motion. And chickens are like tiny, feathered dinosaurs. Colonel Sanders is our John Hammond. We are so screwed. (As a scientist, I would be remiss if I didn’t tell you that the T. rex vision claims of Jurassic Park are completely bonkers and quite wrong. Still, the chicken vision part is quite cool.)
Zoom Info

Via neuronympho:

Did you know chickens ‘one-up’ humans in ability to see color?

Scientists mapped five types of light receptors in the chicken’s eye. They discovered the receptors were laid out in interwoven mosaics that maximized the chicken’s ability to see many colors in any given part of the retina, the light-sensing structure at the back of the eye….

“The human retina has cones sensitive to red, blue and green wavelengths,” Corbo explains. “Avian retinas also have a cone that can detect violet wavelengths, including some ultraviolet, and a specialized receptor called a double cone that we believe helps them detect motion.”

Detect motion?

Wait. In Jurassic Park, the T. rex sensed motion.

And chickens are like tiny, feathered dinosaurs. Colonel Sanders is our John Hammond.

We are so screwed.

(As a scientist, I would be remiss if I didn’t tell you that the T. rex vision claims of Jurassic Park are completely bonkers and quite wrong. Still, the chicken vision part is quite cool.)

Always Check Your Blind Spot (Check the end of this post for a cool way to test your eyes’ blind spot!) Humans have fairly good vision, as the animal world goes. Perhaps not as advanced as some ultraviolet-sensing birds or the super-seeing mantis shrimp, which can see circularly polarized light from UV to infrared, but pretty good. But along the evolutionary path that our eyes took to become what they are today, they left a blind spot … literally. The rod and cone cells that make up the light-sensing part of the retina are wired from the inside, like a camera whose interior is filled with wires. All of those wires have to exit out the back of the eye, leaving a tiny hole in the retina where you can’t see anything: Our eyes are on the left in the image above. The eyes on the right? Cephalopod eyes, like those of squid, have retinas that are wired from beneath and don’t have a blind spot. This is probably why we are doomed to be conquered by them … Want to test your blind spot? Open up the “R/L” image at the top of this post, then close your right eye. Stare at the letter “L” with your left eye and move your head closer and farther from the screen to watch the other letter disappear. Rinse, repeat, freak out.
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Always Check Your Blind Spot

(Check the end of this post for a cool way to test your eyes’ blind spot!)

Humans have fairly good vision, as the animal world goes. Perhaps not as advanced as some ultraviolet-sensing birds or the super-seeing mantis shrimp, which can see circularly polarized light from UV to infrared, but pretty good. But along the evolutionary path that our eyes took to become what they are today, they left a blind spot … literally.

The rod and cone cells that make up the light-sensing part of the retina are wired from the inside, like a camera whose interior is filled with wires. All of those wires have to exit out the back of the eye, leaving a tiny hole in the retina where you can’t see anything:

image

Our eyes are on the left in the image above. The eyes on the right? Cephalopod eyes, like those of squid, have retinas that are wired from beneath and don’t have a blind spot. This is probably why we are doomed to be conquered by them …

Want to test your blind spot? Open up the “R/L” image at the top of this post, then close your right eye. Stare at the letter “L” with your left eye and move your head closer and farther from the screen to watch the other letter disappear.

Rinse, repeat, freak out.

How We See Color

One of the most mind-boggling parts of color theory is the observation that two different colors of light, when mixed, can create a new color. For instance, red and green light shining together, like from the pixels of a TV or computer screen, give the perception of yellow. This is a phenomenon called “additive color” mixing, illustrated below:

image

It turns out that the word “perception” is the key there. Different colors of light each have their own characteristic wavelength and the yellow coming from your monitor is still red and green wavelengths traveling simultaneously toward your eye. The perception of yellow, or any “in-between” color, comes from simultaneously activating more than one kind of “cone” color receptor in the back of your eye. See how yellow, which by itself would have a wavelength of around 570 nm, falls between the red and green cone receptor ranges:

That explanation up there is thanks to another great video by the folks at TED Ed. Check out my previous vision posts here, including OK Go and Sesame Street explaining primary colors, a fun test of your ability to tell colors apart, and an exploration of the idea that Vincent Van Gogh may have been colorblind.

Also, XKCD did a really fun color survey to discover what people in different cultures and from different backgrounds called different hues. The results are amazing (below), be sure to read about the whole project here.

image

Source: youtube.com

Into the Red Can I recommend some tunes to listen to while reading this post? How about this? Or if you’re feeling reggae, then this. A team of vision scientists has engineered a color vision receptor to be more sensitive and see farther into the red than any human! The human eye contains two types of light receptors, rods and cones. The three types of cone cells are what gives us color vision. Each type of cone cell is sensitive to a different range of wavelengths, and added together, they cover our “visible spectrum” from violet to red (~390 nm to 750 nm). It’s like the RGB pixels in a screen, only in reverse. The proteins inside those cones (called “opsins”) actually absorb light and turn it into a chemical signal. It’s one of evolution’s finest bits of magic. I mean, it’s a protein, that absorbs radiation of a very certain wavelength, transfers some charges and shapes, and makes a nerve fire. It’s mind-boggling, man! This new research took one of those opsins and tweaked it so that it can absorb the farthest red light wavelengths better than our own eyes can. By tweaking the order and charge of the amino acids that make up the red opsin, they changed the wavelengths of light it responds most strongly to (from 587 nm to 644 nm). Since each cone sees a range of wavelengths instead of a narrow few, this means it can absorb a little bit of that far red light that our eyes can’t. It hasn’t been put into any kind of living thing yet, only played with in a test tube, but it will help us understand how different opsins in different animals let them see different wavelengths of light (like how mantis shrimp can see ultraviolet light). Maybe one day we’ll create a super-sensory mouse or something, but for now we can be happy just to see how we see a little more clearly. If you’ve got access to Science, you can read about it here. Previously: Was Van Gogh colorblind? Could Monet see ultraviolet?
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Into the Red

Can I recommend some tunes to listen to while reading this post? How about this? Or if you’re feeling reggae, then this.

A team of vision scientists has engineered a color vision receptor to be more sensitive and see farther into the red than any human!

The human eye contains two types of light receptors, rods and cones. The three types of cone cells are what gives us color vision. Each type of cone cell is sensitive to a different range of wavelengths, and added together, they cover our “visible spectrum” from violet to red (~390 nm to 750 nm). It’s like the RGB pixels in a screen, only in reverse.

The proteins inside those cones (called “opsins”) actually absorb light and turn it into a chemical signal. It’s one of evolution’s finest bits of magic. I mean, it’s a protein, that absorbs radiation of a very certain wavelength, transfers some charges and shapes, and makes a nerve fire. It’s mind-boggling, man! This new research took one of those opsins and tweaked it so that it can absorb the farthest red light wavelengths better than our own eyes can.

By tweaking the order and charge of the amino acids that make up the red opsin, they changed the wavelengths of light it responds most strongly to (from 587 nm to 644 nm). Since each cone sees a range of wavelengths instead of a narrow few, this means it can absorb a little bit of that far red light that our eyes can’t.

It hasn’t been put into any kind of living thing yet, only played with in a test tube, but it will help us understand how different opsins in different animals let them see different wavelengths of light (like how mantis shrimp can see ultraviolet light). Maybe one day we’ll create a super-sensory mouse or something, but for now we can be happy just to see how we see a little more clearly.

If you’ve got access to Science, you can read about it here.

Previously: Was Van Gogh colorblind? Could Monet see ultraviolet?