Here is the full transcript of neuroscientist Bryan William Jones’ talk titled “How Your Vision Determines Your Reality” at TEDxBerlin 2024 conference.
Listen to the audio version here:
TRANSCRIPT:
The Human Brain
This amazing object is a human brain. I don’t have one here to show you, but if I could get you to imagine holding one in your own hands, you’d have an object in your hands that is roughly 1.4 kilos of fat, water, protein, carbohydrates, and salt. That’s it. But everything that we are, all of our personality, everything exists in this wondrous object.
And this wondrous object is contained within our skulls. In our skulls, our brains are basically in black boxes, and they know nothing about the world outside, unless it’s informed by the senses that plug into the brain. There are 12 cranial nerves in the brain, and all of our senses plus some end up flowing into our brains to help us synthesize our reality.
The trick is, every one of us perceives the world a little bit differently, but we don’t know it unless we’re given the opportunity to compare what we think we know about the world with what others think they know about the world. Neuroscientists now recognize a broader range of sensory experiences beyond the five basic human senses, with at least 20 senses that have evolved throughout evolution.
We rely on all of these 20 senses as a sophisticated network to literally help us synthesize our reality moment by moment. When there are gaps in the streaming of sensory information into our brains, our brains will make up the difference. They will model or predict what our brains think about reality, almost like we’re along for the ride.
Vision and the Retina
This modeling basically is our reality, but it’s also the foundation of illusion and misunderstanding. My scientific career has been the study of just one of these senses, vision. Vision is the sense that a lot of us use to inform what we think we know about reality.
I’m a neuroscientist who studies a small piece of the brain called the retina at the backs of our eyes. The goal of my work is to understand how retinal neurons are wired together, forming circuits, and how those circuits break in diseases that rob us of vision, like retinitis pigmentosa, age-related macular degeneration, and glaucoma. These are diseases that may be affecting some of us in this room right now.
Certainly as we grow older, about 20% of us will suffer from at least one of these diseases. When we develop in utero, our eyeballs come off the stalks from our brains and start forming all the components of our vision, of our eyeballs. What we have here is a cartoon of an eyeball with the cornea at the front of the eye.
That’s the clear, transparent object. This is where surgeons operate on when they do vision correction surgery. After that comes the lens. The lens is what gets replaced when we have cataracts. In blue around the lens is the iris. The iris gives us the color of our eyes, blue, green, or brown. And in back, in pink, is the retina and the optic nerve.
The Complexity of the Retina
The retina is not normally pink. The retina is normally thin, transparent, like wet tissue paper lining the back of the eye. But this wet tissue paper looking thing belies its complexity. So the retina is actually a sophisticated computing device with image detecting at the back of the retina with retina neurons in front that have circuitry, and all that circuitry calculates everything that we know as the first parts of vision.
The ancient Greeks thought that vision came from within the eyes, that we broadcast the world out through our eyes into what we could see, kind of like virtual reality. We know now that that’s not correct. We know that photons come into the eye and land on photoreceptors at the backs of our eyes, and that’s how we start communicating vision, calculating vision.
It turns out that this thing that we call vision is complicated, even for those of us who study vision. And the more we look, the deeper we look, the more complex vision gets. But one of the things I love about studying vision is that it reveals how different we all are.
Each one of us sees the world a little differently, and in vision, we can effectively communicate this with a couple of exercises here. This is a photograph made by a friend of mine, David Hobby, on a trip that a group of friends made to Cuba. And I’ll use it to show a few examples of what I mean by our sensory paradigms can be different, and thus our realities can be different.
Differences in Visual Perception
Because our senses are filters that help us create our realities, many of us synthesize in our brains a different reality based upon differences in our visual systems. And again, the convenient thing about vision is that we can easily demonstrate this. So some of us have very good vision, and we see the world in 20-20, very sharp.
Some of us are myopic, meaning that we see well up close, but we don’t see so well far away. But thankfully, we’ve got an old technology, glasses, that can help us see well. These glasses help us all live in the same shared reality.
But some of us, upwards of 8% of males specifically, are colorblind. This animation shows what the world looks like to people with the two most common kinds of colorblindness, protanopia and deuteranopia. So colorblind people see color, just not in the same way that people see color with three colors.
They see just fine, but their retinal biology renders a reality that confuses red and green or blue and yellow. And there’s good evidence that suggests that there are some genetic females that see the world in four colors. They see a slightly richer world than those of us who see the world in three colors.
Color Perception in Animals
And if you think that’s cool, there are organisms like turtles, common turtles, that see the world in nominally seven colors.
They see a richness of color that we can’t even imagine in our heads. So, most of the time, people who see the world in three colors agree on what reality is with people that see the world in two colors, with the possible exception of some confusion about certain colors.
And in fact, a lot of the times, people who are colorblind don’t even know that they’re colorblind until an opportunity comes along, or a challenge comes along, that illustrates to them how their reality is fundamentally different from somebody who sees the world in three colors. And judging from the size of this audience, there’s probably 30 people in this room who are colorblind.
Most of the time, each of our brains tends to agree with other brains on what reality is. And this, again, is based upon our shared understanding of the world through our senses. Do you remember this from back in 2015?
Sometimes an event comes along like the dress, right? And the dress revealed this fundamental rift in how people see the world in really new and surprising ways. For vision scientists, particularly vision scientists that study color perception, the dress was a phenomenon, right?
It was like this mass experiment that allowed us to get some insight into how people view the world. So, let’s do a little experiment. Can we get the house lights up a little bit? Is that possible? Awesome.
All right. Almost half the world sees the dress as blue and black. The other half of the world sees it as white and gold, with about 10% of people see it as blue and brown. So, can we have a show of hands? How many people in the room see the dress as blue and black? Raise your hands.
This is fun. Okay. Put your hands down. How many people in the room see the dress as white and gold? Yeah. All right. How many people in the room see the dress as blue and brown? This is awesome, right?
And this tickles me because this worked. The reason this is cool is there are almost a thousand people in this room. And we are all experiencing three completely different realities at the same time.
Color as a Shared Illusion
It turns out how we see the dress is based upon our perceptions of color and prior experience and what we expect color to be. That’s the simplest explanation. But the other really, really cool thing about this experiment is the degree of certainty that people have about what color they see the dress as. And there’s very little confusion on this, right? People see the dress how they see it and that is their reality.
Here’s where I get to say something controversial. And it’s only controversial because of these really strongly held beliefs that we have about what we think reality is. We think about color as being intrinsic to the universe. That everything in the universe has some sort of color to it.
But the truth is there is no color in the world. Let me repeat that. There is no color in the world. Photons, the things that fly into our eyes and trigger photoreceptors at the backs of our retinas, have no color.
Color is an illusion that socially, culturally, and as a species, we share. It’s a shared illusion. It’s wild, right? How do you explain to somebody what color the sky is?
Explaining Color
You say it’s blue. But what’s blue? You could give me a technical explanation for the wavelength of the sky. You could give me a technical explanation for the wavelength of blue and you could talk about luminance and you could talk about hue.
But what’s blue? Imagine trying to explain what blue is to somebody who’s been blind from birth. It can be a daunting task, right, to describe something so fundamental to our understanding of reality.
This shared illusion is created by the biology of neurons in our retinas and in our brains. And these neurons have evolved to interpret electromagnetic energy from this G-type main sequence star known as the yellow dwarf. That is our sun.
Our sun defines what we call vision through the energy that it gives off. And this energy is basically the architect of what we think color is. So this is a movie created by NASA’s Solar Dynamics Observatory. And I show this to give some idea of the kinds of energy that are generated by fusion in the sun.
Electromagnetic Energy and Color Perception
Some of that energy is released as heat that makes life possible on Earth. Some of that energy is released as photons that fly through space and land on Earth and have influenced evolution. So what do I mean by there is no color?
Our neural systems fundamentally operate by comparing things. We compare senses through time. We compare senses against one another. And our brains are constantly comparing these inputs against one another and comparing them.
Prior experience is important with this, but novel input is also integrated into these models of what we think the world looks like. So what we think of as color is created by our brain’s interpretation of the electromagnetic emissions from the sun, specifically the wavelength of photons.
So it turns out that this rainbow that we see is red, green, blue, and all the colors in between is sort of like a Goldilocks zone, right? It’s a perfect sort of zone for vision. Wavelengths on the left side of the rainbow over here, radio, microwave, and infrared are too low energy or they generate heat in tissues.
The Visible Light Spectrum
Wavelengths on the right side of the rainbow, ultraviolet, x-ray, and gamma rays are too high energy, right? They break chemical bonds in our tissues. But wavelengths in the middle are just right for the photoreceptors in our eyes.
So we’ve known since 1872, in experiments by James Clark Maxwell, that photoreceptors respond only to those photons that match wavelengths in a molecule in photoreceptors called opsin. And it turns out, within this range of light, from 400 to 700 nanometers, their correspondence is extremely low.
There corresponds a set of opsins in photoreceptors in our retina that match what we perceive as blue light at 420 nanometers, green light at 534 nanometers, and red light at 564 nanometers, with a peak at 500 nanometers for the rods, which are low light sensitivity photoreceptors that encode no color. So our eyes evolved to be light capturing devices, and the photoreceptors in our retinas have evolved to basically be biological antennas for photon energies between 400 and 700 nanometers.
Our brains perceive these differences in weighting between wavelengths as colors. But the colors don’t exist in nature. What we perceive are basically combinations of wavelengths that we associate with things that are important to us. These are things that are important for our survival. They’re food. They’re sources for reproduction.
Conclusion
So I’m going to leave you today with the idea that we’ve talked about color, and we’ve talked about vision, and how each of us lives in slightly different realities. But we all live on continuums in all of our 20 senses, or more senses. Some of us have deficits in these senses that influence how we perceive the world.
Others of us have different ways of processing the information from these senses that are different from the people around us, and that renders a different reality for us. In other words, we all perceive and process the world a little differently from one another, but we generally agree on what reality is.
So, as our world gets more chaotic and divisive, I would like to encourage you to sort of recognize this, and default to compassion and kindness by recognizing in everyone around us the richness of the diversity of our experiences. Thank you.