Category Archives: How I see things

Do you see only three colors? I see a lot more.


I have been enjoying the book The Future of the Mind, by physicist Michio Kaku. It is interesting and well researched, but he does make one statement that I have to take issue with. He says that humans “see” only three colors. This is not the first time I have heard this claim from someone who ought to know better. (I suspect that vision experts he consulted for the book told him this, and he didn’t question it.)

The notion that we see only three colors is based on the fact that there are three primary colors and we have three types of color photoreceptors, or cones, in our retinas. The idea is wrong, however, on two counts.

For starters, it is important to understand that our eyes detect all frequencies of light in the visible spectrum. We are not limited to the three primary colors. In fact, each type of cone has a response function that spans most of the visible light spectrum. The response peaks at a different spectral frequency for each cone type, and it tapers off as the frequency gets further from the optimum for that type. The peaks do not even correspond with red, green, or blue colors.

Almost any frequency of light in the visible spectrum will cause a response in all three types of cones. Our visual systems combine the three response levels to discern the frequency. For example, light with a 500 nanometer wavelength, which has a blue-green shade, results in a strong response from the “green” cones, about 7/10 as strong in the “red” cones, and only about 2/10 as strong in the “blue” cones. That combination of responses allows us to distinguish between various light frequencies. (There is a lot more to it than that, of course. Color can be influenced by context, for example, and we have a remarkable ability to compensate for different types and levels of lighting.)

We need at least two types of cones in order to distinguish frequencies this way, and three are better. With only one type of cone, we could not tell a dim stimulus at the optimal frequency from a brighter stimulus at a less responsive frequency.

With three types of cones, our visual systems can distinguish a rich variety of many colors, more than two million for most people. I don’t know about you, but my perception of those colors is that they are all different, not just one of three.

It is true that color televisions use only the three primary colors, but that is not because those are the only colors we see. Rather, it is because three colors are sufficient to produce an experience of seeing most of the visible spectrum. With the right combinations of those primary colors, we can stimulate the cones at levels nearly identical to the levels produced by other colors of light, fooling the brain into thinking it is seeing the other colors.

But there is another, more mind-blowing problem with the claim that we see only three colors. That statement might lead one to believe that we are missing out on so many other colors in the visible spectrum that we cannot truly see—and that is usually the intent of the person making the claim. It is wrong, though, because there is no color in reality. Light waves have physical properties including wavelength, frequency, photon energy level (all interrelated), and intensity, but not color.

Color is an interpretation imposed by our brains, as a way of making meaningful sense of the complex mix of light frequencies and intensities striking our retinas. We rarely see pure spectral colors, outside of rainbows and reflections from surfaces that diffract light (such as CDs and DVDs). Most everyday objects reflect many different frequencies of light. The color we perceive is a result of the combined sensations caused by that assortment of frequencies. Whatever the total cone response is, our brains assign a corresponding color to it.

Color perception is one of the most profound examples of the way our brains construct representations of the world around us from sensory inputs. As real and as important as color seems to us, it nonetheless originates within our minds. For that reason, there can be no colors other than the ones you see. But for most of us that range of colors is rich and wondrous, and certainly more than three.

Building trust in science

In their book, Unscientific America: How Scientific Illiteracy Threatens Our Future,  Chris Mooney and Sheril Kirshenbaum say that Americans don’t trust science. A lot of that, as they point out, is a result of negative portrayals in television and movies, attacks from politicians and religious groups, and a general disconnect of scientific research from most of our daily lives.

I have always revered science, or at least the classical scientific principles that have been proven over time. Just as I would rather listen to classical music than the latest hits, or get my information from books instead of streaming newscasts, I tend to prefer the thoroughly digested long-term overview of science over the day-to-day research process.

When we get down to day-to-day findings, or even decade-to-decade findings, science hasn’t always earned our trust. The same people who brought us “better living through chemistry” also brought us bisphenol-A, PCBs, Agent Orange, and a host of household chemicals with dangers and toxicity levels that the average person is either unaware of or chooses to ignore. Science has overall raised our standard of living, but it has also led to overpopulation as food has become more plentiful, people live longer, and many diseases have been eradicated or made less severe. We are more comfortable, healthier, and able to enjoy life more than ever, and yet there is a sense of loss in that we seem to have more and more odd seasons–here in northeast Ohio we seem to have a lot of unusually warm winters and cool summers of late. Visit a park like Smoky Mountain National Park today and it just doesn’t have the feeling of wilderness that it used to have. It hasn’t been developed any more than it used to be, but as more people visit the park it just doesn’t feel like you are getting as close to nature as you used to feel. As we build more roads, buy more cars, and develop more suburbs, things start to look the same everywhere you go–I loved the term Generica that someone coined for the strip malls that all have the same stores and restaurants. Admittedly, all of these observations are indirectly a result of the science that made them possible. It is perhaps unfair to blame science for it, because it has more to do with how people have chosen to use the science.

In pure scientific research we see practices that also lead us to suspect scientists’ motives. Researchers receive funding from drug companies to test the effectiveness of the drugs, but do not disclose the funding source. Negative experiment results are simply not reported. In my own field of psychology, all kinds of things can go wrong with experiments. Many researchers do their best to avoid introducing biases or errors into their experiments, but results are often open to interpretation. A lot depends on how the questions are asked or how the results are interpreted. Experiments are supposed to be reproducible, but how often does someone actually try to reproduce any but the most classical experiments that are demonstrated in student labs. More likely, when a result is published, it will motivate someone else to come up with a counterexample or way of demonstrating an opposing view, and a subsequent experiment will argue for the opposite interpretation. Over time we might get to the truth, but it will take a long time to get there.

Great things happening in northeast Ohio

I’m going to say it. I think Clevelanders are being bamboozled by the people pushing for the Medical Mart. They are promising things that are far more optimistic than they can deliver on, and when questioned about it they lash out and tell us that they are our last hope for a dying city. Mr. Kennedy’s remarks that no one wants to do business in Cleveland, and that the only reason he was building the Medical Mart in Cleveland was because of Tim Hagan’s friendship, were nothing short of insulting

The reason I am offended by those comments is that I see a lot of great things happening in this region. When I go to events at OAI, i-Open, Science Cafe, Case Western Reserve University, and other places, I hear about advanced technologies that are putting Ohio on the map. We are home to key players in medical imaging, alternate energy, prosthetics, brain stimulation and neural interfacing, and much more. Our region has an exceptional density of research institutions, tech startups, advanced technology companies, and medical facilities. We are seeing collaborations between many institutions that are producing results far beyond what any one of them can achieve independently.

Northeast Ohio has its share of problems, including political corruption, economic problems, dying industries, a shortage of well educated laborers, and a pessimistic outlook. But I am tired of people looking to The Next Big Project, such as the Medical Mart, as the one thing that is going to bring everyone back. We need to play more to the strengths of the advanced technologies being developed here, our access to one of the largest supplies of fresh water in the world, and a pleasant way of life. And we shouldn’t take abuse from people who think we are desperate enough to give in to their every demand.