Why Humans See More Colors than Dogs, but Fewer than Birds and Insects
“What we perceive as color — what we perceive as light — corresponds to a very narrow band of frequencies, out of an infinite continuum," says Nobel Laureate Frank Wilczek.
Frank Wilczek is an American theoretical physicist, mathematician and a Nobel laureate. He is currently the Herman Feshbach Professor of Physics at the Massachusetts Institute of Technology (MIT). Wilczek, along with David Gross and H. David Politzer, was awarded the Nobel Prize in Physics in 2004 for their discovery of asymptotic freedom in the theory of the strong interaction. He is on the Scientific Advisory Board for the Future of Life Institute. His new book is titled A Beautiful Question: Finding Nature's Deep Design.
Frank Wilczek: In the nineteenth century with Maxwell’s synthesis of the laws of electricity and magnetism physicists started to realize that what we perceive as light is deeply understood as a kind of disturbance, electric and magnetic fields. That gave us a new concept of the possibilities of perception of light that show us that we’re missing a lot. The electromagnetic equations permit radiation of any wave length and of any frequency – what we perceive as color – what we perceive as light is corresponds to a very narrow band of frequencies out of an infinite continuum. Not only that but even within that band we take three averages. We don’t sample all the different frequencies but just three averages. That’s called trichromatic vision. So for instance in computer displays there are three different kinds of lighting elements used. When you see on your menu the choice of millions of different colors that doesn’t mean different lighting arrangements, lighting possibilities. It means different combinations, different relative intensities of just three. Any perceived color can be synthesized from three basic colors.
Other creatures see less. Dogs, for instance, see only two kinds of colors like color blind people see basically only two kinds of colors. Other creatures see more. Other creatures – many insects and birds see four or five colors. They also sample kinds of light, kinds of electromagnetic radiation that humans don’t see. There’s infrared radiation. There’s ultraviolet radiation. Maxwell’s equations which describe light also describe radio waves and microwaves and x-rays and gamma rays. So all those things are possible forms of vision that human’s natural endowment doesn’t tap into. But it’s out there. On the one hand it’s very important to make concepts visual because it taps into very powerful methods of processing that we have. And on the other hand scientific knowledge of what light is shows us that our natural perception leaves a lot on the table and so it leaves us with the program of doing better with telescopes, microscopes, spectrometers and other kinds of gadgets that I’m developing for everyday life that will allow us to see more colors.
The human perception of color is limited really by the principles of quantum mechanics. It’s interesting to compare the human perception of color to the perception of sound. Our perception of sound in one way is much richer. When you have two pure tones together like a C and a G, a simple chord that’s a fifth. If you hear that you can hear the separate tones even though they’re played together and you hear a chord. You can also sense the separate tones and if one is louder than the other you can continuously judge how their relative intensity. Whereas with colors if you mix two different – if you have two different colors say spectral green and spectral red and mix them what you see is not a chord where you can see the distinct identities preserved but rather an intermediate color. In fact you’ll see something that looks like yellow. The perception of color sort of throws away the detailed resolution, detailed accounting of the different kinds of underlying tones, different kinds of pure frequencies or pure colors that are underlying the perception. Our perception of that kind of mixture is indistinguishable from our perception of a pure spectral yellow such as you’d see in a rainbow.
It’s as if in music when you played a C and a G together instead of hearing a chord you just heard the note E, the intermediate note. On the other hand visual information is much richer in conveying the spatial structure of things. We get a detailed image whereas sound gives much poorer spatial resolution. And there are good physical reasons for those things. Sound waves are relatively slow – oscillate relatively slowly so that mechanical vibrations inside our ear and electrical processes inside our brain can keep up with them and so we can keep that kind of time structure. We can keep track of it. That’s why we do a good job with chords. Whereas the oscillations in electromagnetic radiation are very, very fast. Much faster than any mechanical system can keep up with or that nerve firings can keep up with. So the way we process that is quite different. It’s an all or none process where photons get absorbed and trigger changes in the structure of proteins. And we have three kinds of proteins and three different kinds of cone cells that give us three kinds of average responses. And that’s why you can synthesize any perceived color with just three.
"In the nineteenth century, with Maxwell’s Synthesis of the Laws of Electricity and Magnetism, physicists started to realize that what we perceive as light is deeply understood as a kind of disturbance of electric and magnetic fields." Frank Wilczek says. "That gave us a new concept of the possibilities of perception of light, that show us we’re missing a lot."
In fact, there is a lot to light that we as humans can’t see.
"What we perceive as color — what we perceive as light — corresponds to a very narrow band of frequencies, out of an infinite continuum. Not only that, but within that band we take three averages."
These averages are made up of the three primary colors. These three colors mix and match to make up the rest of our field of vision, which is known as tri-chromatic vision.
"In computer displays, there are three different kinds of lighting elements used." Wilczek explains. "When you see on your menu, the choice of millions of different colors, that doesn’t mean different lighting arrangements or possibilities. It means different combinations, different relative intensities of just three. Any perceived color can be synthesized from three basic colors."
Not all animals have three cones of vision, dogs are known to have only two, while some other animals have more. These animals not only can see more colors than we as humans do, but can "sample" light in different ways than humans, such as infrared and ultra violet light. For now, in our current natural state of being, we can’t see them.
"Our perception of sound, in one way, is much richer." Wilczek says. When a chord is played on an instrument, we are able to differentiate between the notes being played, we hear them as separate notes played at the same time. But when two waves of light, two colors hit each other, such as red and blue, we see them as one beam of light: purple.
"Our perception of that mixture is indistinguishable from a pure spectral yellow such as you’d see in a rainbow. It’s as if in music, when you play a C and a G together, instead of hearing a chord, you just heard the note E."
This has a lot to do with how fast the waves oscillate. Sound waves are relatively slower, allowing our brains to keep up with the way they move, while light waves oscillate faster.
"The way we process that is quite different, it’s an all or none process where photons get absorbed and trigger changes in the structure of proteins. We have three kinds of proteins, and three different kinds of cone cells, that give us three kinds of average responses. And that’s why you can synthesize any perceived color with just three."
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That's as fast as a bullet train in Japan.
The way an elephant manipulates its trunk to eat and drink could lead to better robots, researchers say.
Elephants dilate their nostrils to create more space in their trunks, allowing them to store up to 5.5 liters (1.45 gallons) of water, according to their new study.
They can also suck up three liters (0.79 gallons) per second—a speed 30 times faster than a human sneeze (150 meters per second/330 mph), the researchers found.
The researchers wanted to better understand the physics of how elephants use their trunks to move and manipulate air, water, food, and other objects. They also wanted to learn if the mechanics could inspire the creation of more efficient robots that use air motion to hold and move things.
Photo by David Clode on Unsplash
While octopuses use jets of water to propel themselves and archer fish shoot water above the surface to catch insects, elephants are the only animals able to use suction both on land and underwater.
"An elephant eats about 400 pounds of food a day, but very little is known about how they use their trunks to pick up lightweight food and water for 18 hours, every day," says lead author Andrew Schulz, a mechanical engineering PhD student at the Georgia Institute of Technology. "It turns out their trunks act like suitcases, capable of expanding when necessary."
Sucking up tortilla chips without breaking them
Schulz and his colleagues worked with veterinarians at Zoo Atlanta, studying elephants as they ate various foods. For large rutabaga cubes, for example, the animal grabbed and collected them. It sucked up smaller cubes and made a loud vacuuming sound, like the sound of a person slurping noodles, before transferring the vegetables to its mouth.
To learn more about suction, the researchers gave elephants a tortilla chip and measured the applied force. Sometimes the animal pressed down on the chip and breathed in, suspending the chip on the tip of its trunk without breaking it, similar to a person inhaling a piece of paper onto their mouth. Other times the elephant applied suction from a distance, drawing the chip to the edge of its trunk.
Elephants inhale at speeds comparable to Japan's 300 mph bullet trains.
"An elephant uses its trunk like a Swiss Army knife," says David Hu, Schulz's advisor and a professor in Georgia Tech's School of Mechanical Engineering. "It can detect scents and grab things. Other times it blows objects away like a leaf blower or sniffs them in like a vacuum."
By watching elephants inhale liquid from an aquarium, the team was able to time the durations and measure volume. In just 1.5 seconds, the trunk sucked up 3.7 liters (just shy of 1 gallon), the equivalent of 20 toilets flushing simultaneously.
Soft robots and elephant conservation
The researchers used an ultrasonic probe to take trunk wall measurements and see how the trunk's inner muscles work. By contracting those muscles, the animal dilates its nostrils up to 30%. This decreases the thickness of the walls and expands nasal volume by 64%.
"At first it didn't make sense: an elephant's nasal passage is relatively small and it was inhaling more water than it should," Schulz says. "It wasn't until we saw the ultrasonographic images and watched the nostrils expand that we realized how they did it. Air makes the walls open, and the animal can store far more water than we originally estimated."
Based on the pressures applied, Schulz and the team suggest that elephants inhale at speeds comparable to Japan's 300-mph bullet trains.
"By investigating the mechanics and physics behind trunk muscle movements, we can apply the physical mechanisms—combinations of suction and grasping—to find new ways to build robots," Schulz says.
"In the meantime, the African elephant is now listed as endangered because of poaching and loss of habitat. Its trunk makes it a unique species to study. By learning more about them, we can learn how to better conserve elephants in the wild."
The paper appears in the Journal of the Royal Society Interface. The US Army Research Laboratory and the US Army Research Oﬃce 294 Mechanical Sciences Division, Complex Dynamics and Systems Program, funded the work. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the view of the sponsoring agency.
Source: Georgia Tech
Original Study DOI: 10.1098/rsif.2021.0215
The experience of life flashing before one's eyes has been reported for well over a century, but where's the science behind it?
At the age of 16, when Tony Kofi was an apprentice builder living in Nottingham, he fell from the third story of a building. Time seemed to slow down massively, and he saw a complex series of images flash before his eyes.
As he described it, “In my mind's eye I saw many, many things: children that I hadn't even had yet, friends that I had never seen but are now my friends. The thing that really stuck in my mind was playing an instrument". Then Tony landed on his head and lost consciousness.
When he came to at the hospital, he felt like a different person and didn't want to return to his previous life. Over the following weeks, the images kept flashing back into his mind. He felt that he was “being shown something" and that the images represented his future.
Later, Tony saw a picture of a saxophone and recognized it as the instrument he'd seen himself playing. He used his compensation money from the accident to buy one. Now, Tony Kofi is one of the UK's most successful jazz musicians, having won the BBC Jazz awards twice, in 2005 and 2008.
Though Tony's belief that he saw into his future is uncommon, it's by no means uncommon for people to report witnessing multiple scenes from their past during split-second emergency situations. After all, this is where the phrase “my life flashed before my eyes" comes from.
But what explains this phenomenon? Psychologists have proposed a number of explanations, but I'd argue the key to understanding Tony's experience lies in a different interpretation of time itself.
When life flashes before our eyes
The experience of life flashing before one's eyes has been reported for well over a century. In 1892, a Swiss geologist named Albert Heim fell from a precipice while mountain climbing. In his account of the fall, he wrote is was “as if on a distant stage, my whole past life [was] playing itself out in numerous scenes".
More recently, in July 2005, a young woman called Gill Hicks was sitting near one of the bombs that exploded on the London Underground. In the minutes after the accident, she hovered on the brink of death where, as she describes it: “my life was flashing before my eyes, flickering through every scene, every happy and sad moment, everything I have ever done, said, experienced".
In some cases, people don't see a review of their whole lives, but a series of past experiences and events that have special significance to them.
Explaining life reviews
Perhaps surprisingly, given how common it is, the “life review experience" has been studied very little. A handful of theories have been put forward, but they're understandably tentative and rather vague.
For example, a group of Israeli researchers suggested in 2017 that our life events may exist as a continuum in our minds, and may come to the forefront in extreme conditions of psychological and physiological stress.
Another theory is that, when we're close to death, our memories suddenly “unload" themselves, like the contents of a skip being dumped. This could be related to “cortical disinhibition" – a breaking down of the normal regulatory processes of the brain – in highly stressful or dangerous situations, causing a “cascade" of mental impressions.
But the life review is usually reported as a serene and ordered experience, completely unlike the kind of chaotic cascade of experiences associated with cortical disinhibition. And none of these theories explain how it's possible for such a vast amount of information – in many cases, all the events of a person's life – to manifest themselves in a period of a few seconds, and often far less.
Thinking in 'spatial' time
An alternative explanation is to think of time in a “spatial" sense. Our commonsense view of time is as an arrow that moves from the past through the present towards the future, in which we only have direct access to the present. But modern physics has cast doubt on this simple linear view of time.
Indeed, since Einstein's theory of relativity, some physicists have adopted a “spatial" view of time. They argue we live in a static “block universe" in which time is spread out in a kind of panorama where the past, the present and the future co-exist simultaneously.
The modern physicist Carlo Rovelli – author of the best-selling The Order of Time – also holds the view that linear time doesn't exist as a universal fact. This idea reflects the view of the philosopher Immanuel Kant, who argued that time is not an objectively real phenomenon, but a construct of the human mind.
This could explain why some people are able to review the events of their whole lives in an instant. A good deal of previous research – including my own – has suggested that our normal perception of time is simply a product of our normal state of consciousness.
In many altered states of consciousness, time slows down so dramatically that seconds seem to stretch out into minutes. This is a common feature of emergency situations, as well as states of deep meditation, experiences on psychedelic drugs and when athletes are “in the zone".
The limits of understanding
But what about Tony Kofi's apparent visions of his future? Did he really glimpse scenes from his future life? Did he see himself playing the saxophone because somehow his future as a musician was already established?
There are obviously some mundane interpretations of Tony's experience. Perhaps, for instance, he became a saxophone player simply because he saw himself playing it in his vision. But I don't think it's impossible that Tony did glimpse future events.
If time really does exist in a spatial sense – and if it's true that time is a construct of the human mind – then perhaps in some way future events may already be present, just as past events are still present.
Admittedly, this is very difficult to make sense of. But why should everything make sense to us? As I have suggested in a recent book, there must be some aspects of reality that are beyond our comprehension. After all, we're just animals, with a limited awareness of reality. And perhaps more than any other phenomenon, this is especially true of time.
A school lesson leads to more precise measurements of the extinct megalodon shark, one of the largest fish ever.
- A new method estimates the ancient megalodon shark was as long as 65 feet.
- The megalodon was one of the largest fish that ever lived.
- The new model uses the width of shark teeth to estimate its overall size.
A Florida student figured out a way to more accurately measure the size of one of the largest fish that ever lived – the extinct megalodon shark – and found that it was even larger than previously estimated.
The megalodon (officially named Otodus megalodon, which means "Big Tooth") lived between 3.6 and 23 million years ago and was thought to be about 34 feet long on average, reaching the maximum length of 60 feet. Now a new study puts that number at up to 65 feet (20 meters).
Homework assignment leads to a discovery
The study, published in Palaeontologia Electronica, used new equations extrapolated from the width of megalodon's teeth to make the improved estimates. The paper's lead author, Victor Perez, developed the revised methodology while he was a doctoral student at the Florida Museum of Natural History. He got the idea while teaching students, noticing a range of discrepancies in the results they were getting.
Students were supposed to calculate the size of megalodon based on the ancient fish's similarities to the modern great white shark. They utilized the commonly accepted method of linking the height of a shark's tooth to its total body length. As the press release from the Florida Museum of Natural History expounds, this method involves locating the anatomical position of a tooth in the shark's jaw, measuring the tooth "from the tip of the crown to the line where root and crown meet," and using that number in an appropriate equation.
But while carrying out calculations in this way, some of Perez's students thought the shark would have been just 40 feet long, while others were calculating 148 feet. Teeth located toward the back of the mouth were yielding the largest estimates.
"I was going around, checking, like, did you use the wrong equation? Did you forget to convert your units?" said Perez, currently the assistant curator of paleontology at the Calvert Marine Museum in Maryland. "But it very quickly became clear that it was not the students that had made the error. It was simply that the equations were not as accurate as we had predicted."
Found in North Carolina, these 46 fossils are the most complete set of megalodon teeth ever excavated.Credit: Jeff Gage/Florida Museum
The new approach
Perez's math exercise demonstrated that the equations in use since 2002 were generating different size estimates for the same shark based on which tooth was being measured. Because megalodon teeth are most often found as standalone fossils, Perez focused on a nearly complete set of teeth donated by a fossil collector to design a new approach.
Perez also had help from Teddy Badaut, an avocational paleontologist in France, who suggested using tooth width instead of height, which would be proportional to the length of its body. Another collaborator on the revised method was Ronny Maik Leder, then a postdoctoral researcher at the Florida Museum, who aided in the development of the new set of equations.
The research team analyzed the widths of fossil teeth that came from 11 individual sharks of five species, which included megalodon and modern great white sharks, and created a model that connects how wide a tooth was to the size of the jaw for each species.
"I was quite surprised that indeed no one had thought of this before," shared Leder, who is now director of the Natural History Museum in Leipzig, Germany. "The simple beauty of this method must have been too obvious to be seen. Our model was much more stable than previous approaches. This collaboration was a wonderful example of why working with amateur and hobby paleontologists is so important."
Why use teeth?
In general, almost nothing of the super-shark survived to this day, other than a few vertebrae and a large number of big teeth. The megalodon's skeleton was made of lightweight cartilage that decomposed after death. But teeth, with enamel that preserves very well, are "probably the most structurally stable thing in living organisms," Perez said. Considering that megalodons lost thousands of teeth during a lifetime, these are the best resources we have in trying to figure out information about these long-gone giants.
Researchers suggest megalodon's large jaws were very thick, made for grabbing prey and breaking its bones, exerting a bite force of up to 108,500 to 182,200 newtons.
Megalodon tooth compared to two great white shark teeth. Credit: Brocken Inaglory / Wikimedia.
Limitations of the new model
While the new model is better than previous methods, it's still far from perfect in precisely figuring out the sizes of animals which lived so long ago and left behind few if any full remains. Because individual sharks come in a variety of sizes, Perez warned that even their new estimates have an error range of about 10 feet when it comes to the largest animals.
Other ambiguities may affect the results, such as the width of the megalodon's jaw and the size of the gaps between its teeth, neither of which are accurately known. "There's still more that could be done, but that would probably require finding a complete skeleton at this point," Perez pointed out.
How did the megalodon go extinct?
Environmental changes that led to fluctuations in sea levels and disturbed ecosystems in the oceans likely led to the demise of these enormous ancient sharks. They were just too big to be sustained by diminishing food resources, says the ReefQuest Centre for Shark Research.
A 2018 study suggested that a supernova 2.6 million years ago hit Earth's atmosphere with so much cosmic energy that it resulted in climate change. The cosmic rays that included particles called muons might have caused a mass extinction of giant ocean animals ("the megafauna") that included the megalodon by causing mutations and cancer.
Scientists, led by Adrian Melott, professor emeritus of physics and astronomy at the University of Kansas, estimated that "the cancer rate would go up about 50 percent for something the size of a human — and the bigger you are, the worse it is. For an elephant or a whale, the radiation dose goes way up," as he explained in a press release.
Might as well face it, you're addicted to love.
- Many writers have commented on the addictive qualities of love. Science agrees.
- The reward system of the brain reacts similarly to both love and drugs
- Someday, it might be possible to treat "love addiction."
Since people started writing, they've written about love. The oldest love poem known dates back to the 21st century BCE. For most of that time, writers also apparently have been of two (or more) minds about it, announcing that love can be painful, impossible to quit, or even addictive — while also mentioning how nice it is.
The idea of love as an addiction is one that is both familiar and unsettling. Surely it can't be the case that our mutual love with our partner — a thing that can produce euphoria, consumes a great deal of our time, and which we fear losing — can be compared to a drug habit? But indeed, many scientists have turned their attention to the idea of "love addiction" and how your brain on drugs might resemble your brain in love.
Love and other drugs
In a 2017 article published in the journal Philosophy, Psychiatry, & Psychology, a team of neuroethicists considered the idea that love is addicting and held the idea up to science for scrutiny.
They point out that the leading model of addiction rests on the notion of a drug causing the brain to release an unnatural level of reward chemicals, such as dopamine, effectively hijacking the brain's reward system. This phenomenon isn't strictly limited to drugs, though they are more effective at this process than other things. Rats can get a similar rush from sugar as from cocaine, and they can have terrible withdrawal symptoms when the sugar crash kicks in.
On the structural level, there is a fair amount of overlap between the parts of the brain that handle love and pair-bonding and the parts that deal with addiction and reward processing. When inside an MRI machine and asked to think about the person they love romantically, the reward centers of people's brains light up like Broadway.
Love as an addiction
These facts lead the authors to consider two ideas, dubbed the "narrow" and "broad" views of love as an addiction.
The narrow view holds that addiction is the result of abnormal brain processes that simply don't exist in non-addicts. Under this paradigm, "food-seeking or love-seeking behaviors are not truly the result of addiction, no matter how addiction-like they may outwardly appear." It could be that abnormal processes cause the brain's reward system to misfire when exposed to love and to react to it excessively.
If this model is accurate, love addiction would be a rare thing — one study puts it around five to ten percent of the population — but could be considered a disorder similar to others and caused by faulty wiring in the brain. As with other addictions, this malfunction of the reward system could lead to an inability to fully live a typical life, difficulty having healthy relationships, and a number of other negative consequences.
The broad view looks at addiction differently, perhaps even radically.
It begins with the idea that addiction exists on a spectrum of motivations. All of our appetites, including those for food and water, exist on this spectrum and activate similar parts of the brain when satisfied. We can have appetites for anything that taps into our reward system, including food, gambling, sex, drugs, and love. For most people most of the time, our appetites are fairly temperate, if recurring. I might be slightly "addicted" to food — I do need some a few times per day — but that "addiction" doesn't have any negative effects on my health.
An appetite for cocaine, however, is rarely temperate and usually dangerous. Likewise, a person's appetite for love could reach addiction levels, and a person could be considered "hooked" on relationships (or on a particular person). This would put love addiction at the extreme end of the spectrum.
None of this is to say that the authors think that love is bad for you just because it can resemble an addiction. Love addiction is not the same as cocaine addiction at the neurological level: important differences, like how long it takes for the desire for another "hit" to occur, do exist. Rather, the authors see this as an opportunity to reconsider our approach to addiction in general and to think about how we can help the heartsick when they just can't seem to get over their last relationship.
Is "love addiction" a treatable disorder?
Hypothetically, a neurological basis for an addiction to love could point toward interventions that "correct" for it. If the narrow view of addiction is accurate, perhaps some people will be able to seek treatment for love addiction in the same way that others seek help to quit smoking. If the broad view of addiction is correct, the treatment of love addiction would be unlikely as it may be difficult to properly identify where the cutoff of acceptability on a spectrum should be.
Either way, since love is generally held in high regard by all cultures and doesn't quite seem to be in the same category as a bad cocaine habit in terms of social undesirability, the authors doubt we'll be treating anyone for "love addiction" anytime soon.