Our senses and “objective reality”: part 1 – vision

[ This is post #4 in the series, “Finding reality in a post truth world.” ]

Homo sapiens has been around for around 200,000 years. Today, we ridicule “flat earthers.” But for 99% of the time homo sapiens existed, everyone was a flat earther. When we consider that somewhere between 30% and 65% of the processing power of the brain is devoted to vision, it’s not surprising that most humans, lacking modern tools of science, thought the earth was flat. You can’t detect the curvature of the earth below 35,000 feet, so that ruled out a “true” perception of “objective reality” simply by climbing up the nearest mountain.

Most of the evolution of homo sapiens, then, occurred with a fundamental misperception of reality. It leads one to wonder whether evolution favors an accurate picture of the “real world,” or does it instead favor an understanding that’s just good enough for evolutionary fitness. That’s the crux of Donald Hoffman’s fascinating book, “The Case Against Reality, why evolution hid the truth from our eyes.”

The starting point of this discussion is, of course, evolution and in particular Darwin’s theory of natural selection, which he sums up as follows:

But if variations useful to any organic being do occur, assuredly individuals thus characterized will have the best chance of being preserved in the struggle for life; and from the strong principle of inheritance they will tend to produce offspring similarly characterized. This principle of preservation, I have called, for the sake of brevity, Natural Selection.

Hoffman, p. 56, from Darwin’s “On the Origin of Species by Means of Natural Selection”

While only around 1/3 of the public believes this to be true, more than 87% of all scientists accept this as established fact. As in all questions of science there is never unanimity, so if you’re not an expert on evolution, it makes sense to go along with the scientific consensus, which here is quite clear.

If one does accept natural selection as fact, then it follows that evolutionary fitness dominates organic development. Why? Because any other strategy, no matter how “beautiful” or “noble” would lead to extinction. Evolutionary fitness might coincide with beauty or nobility, e.g. acts of altruism, but it can’t be the ultimate goal. Reproduction is the goal; everything else is subordinate.

This brings us back to the visual system, which plays a dominant role in our sensory perception of the world. Two questions pop up: a) how good is our visual system in terms of understanding the “real world”?; and b) if it’s not that good, why is it sufficient for natural selection?


To the non-scientific viewer, this seems impressive. Our eye’s grouping of wave lengths in the spectrum is, after all, responsible for much of what we call “beauty.” Without going into anatomical details, it is impressive. We can “see” individual photons; we can perceive a million colors. But when we combine the raw capture power of the eye with the processing of the brain, much of this is filtered out. The result is the eye chart you see at the optician’s office.

We’re used to putting ourselves at the top of the organic world. Let’s see how this holds up for our visual system.

The evidence shows that the human visual system is just so-so in terms of raw capture power. We have tri-chromatic vision, thanks to three opsins –light sensitive proteins found in the retinas of humans and animals. Dragonflies have between 15 and 30 opsins, allowing them to see all the colors we do as well as ultraviolet light. Not only that, but their eyes have up to 30,000 facets, allowing them to see in every direction simultaneously. Their small brains handle the impressive feat of integrating these images into a coherent whole that gives them prowess as hunters.

There are many animals that see much better than humans. Eagles, for example, can spot a rabbit over a mile away. Older humans often have trouble seeing at night, but tigers, lions, jaguars, and leopards have extraordinary night vision, making them dangerous predators. Chameleons have eyes that can swivel, and they can process the image from each eye independently.

Even the highest level of visual acuity pales when compared with the entirety of the electromagnetic spectrum, of which the visible light spectrum is a tiny part, and which, after all, is the closest thing we have to “objective reality.”


I couldn’t resist using xkcd’s drawing on this topic, and even if you strip away all the humor, it still shows the dilemma of homo sapiens for 99.9% of its existence. Our visual perception of the objective world, and the perception that has guided natural selection, is based on a tiny fraction of reality – .0035% to be exact. Our species first became aware of the other 99.9% of the spectrum a little more than a century ago. At the time radio waves were discovered, in the 1880’s, 99.9% of our evolutionary history had already passed us by.

So, when Donald Hoffman poses the question, what’s more important – truth or evolutionary fitness, the answer, at least as far as our visual system is concerned, seems clear. Hoffman uses the metaphor of the desktop icon to describe this. We all know that the icon on our computing device representing email isn’t really email. It’s nothing more than an assembly of pixels representing a complex computing process. So it is with vision. It’s an icon on a huge screen, giving us a tiny slice of objective reality, but enough to facilitate natural selection.

The raw capture power of our vision, combined with the processing power of our brain, allows us to recognize visual patterns, to sense danger, to see beauty (reproductive fitness) in another person. Imagine how confusing the world would be if we sensed every aspect of the electromagnetic spectrum. Not only would our brain have to be the size of a refrigerator, it wouldn’t help us escape from the predator on the savannah about to make a meal out of us. For most of our existence, fitness, rather than “truth,” gave us what we needed to survive. You don’t need to know the earth is a sphere to run away from a lion, but you do need an overabundance of caution when you see movement in a bush, or when you see just a tiny portion of a predator. You do need to visualize your world as a three dimensional surface consisting of solid objects. Perception of molecules in that environment would lead to extinction.

The visual system is not just a dominant part of our brain’s perception of reality; it is also at the core of many cognitive fallacies. The very thing that we’re so good at – pattern recognition – also accounts for stereotypical thinking, tribalism, premature judgements, etc.

Do our other sensory systems make up for these deficiencies? I’ll explore that next.

5 comments on “Our senses and “objective reality”: part 1 – vision

  1. Human vision is remarkable when considering the limitations of physics. Consider our relatively rare ability to focus at a very wide range of distances. Then consider the range of biological materials able to serve as a suitable lens material.

    Also consider the range of illumination our multi-focal eye can utilize. Not the widest range, to be sure, but remarkable given all the other things our eyes can simultaneously perform.

    The human eye also does excellent motion detection. In fact, our sight fails without motion, hence the need for saccades to keep our vision active when looking at still views. But even this facility can fail when viewing a flat field, such as snow (the failure being called snow-blindness). It’s almost like someone turned off the lights, despite all the brightness. Which, oddly enough, is precisely why we can sleep during the day: Our eyelids pass lots of light, but it is so featureless and diffuse that the brain simply stops seeing it!

    I was the engineer responsible for the color correction system for an ultra-high-speed digital video camera (100,000 fps). At full speed, each pixel is essentially counting photons, and the number of photons behind the red, green and blue Bayer filter elements can become indistinguishable. So when colors can’t be distinguished, a monochrome image was produced. Much like the human eye, though through different mechanisms.

    Given enough photons, full-color images could be produced. Which immediately yielded problems: The images that were mathematically best (minimum noise, maximum linearity, minimum adjacent pixel interference, and so on) turned out to look horrible to human observers. Washed out, bland. But the computer, and especially automated vision algorithms, loved the mathematically ideal images.

    My next task was to make images that would help sell our extraordinarily expensive cameras at trade shows. We needed images that “popped” and had a “wow factor” that placed us head-and-shoulders above the competition. Which began my deep dive into human visual perception.

    It turns out that humans “see” relatively little of the “real” world, a situation that degrades when it is a screen being viewed. Pixels are discrete, not continuous. Colors are discrete, not continuous. There are just three colors being emitted, instead of a full spectrum. The number of colors is limited, as are the steps/continuity between adjacent color values.

    Then there is the issue of frame rate. The human visual system basically operates at about 15 Hz, yet we can perceive motion happening at higher rates, and our color perception operates at lower rates. How can a screen with a digital signal ever “fool” (be convincing to) the human eye?

    The digital system must to lie to the human eye. But the lies must be “honest” lies, ones that distort the mathematically ideal sensor data in ways to help the equivalent impression be perceived by the human visual system. First, we “punch up” the colors by adding non-linear emphasis. Then we further increase contrast with another, separate, non-linear “correction”. We add a whiff of edge-enhancement to trigger the eye’s motion sensors. Then we do something paradoxical: We reduce the frame rate and add motion blur.

    There are additional “corrections” being done, but you get the idea: The human eye is not ideally suited to the digital domain, yet the systems can adapt well enough. Similar things apply to human hearing, where they are even more successful.

    Now let’s take our family and social capabilities, and expose them to social media. The adaptation is not nearly as effective. I’m not at all sure we even understand the perceptions and limitations involved.

    1. Thanks for such a perceptive and informative comment. Your final point about the effects of social media are especially appropriate. A couple of weeks ago, my wife and I watched the movie “The Social Dilemma” on Netflix. That complemented another book I read a year ago, Ten Arguments for Deleting Your Social Media Accounts Right Now. As you point out, this is a vast social experiment with long lasting consequences, but without any effective controls go gauge the value of its contribution to society.

      I’m going to give a presentation on all this at a local university when I’m done with it, and I hope you don’t mind if I use your comments here as additional material.

      1. Well, my closing thought on social media was intentionally there to tie into your larger theme.

        Were I to stay in the human visual perception domain, I’d segue to the recent deepfake phenomenon and how human psychology is nearly powerless in its presence. We need to learn whole new ways of seeing, feeling and thinking in this digital age, given the tendency of technologies developed by neutral researchers to be used by industry and governments in the most manipulative ways possible.

        But first we must better describe the problem, its causes and effects, before we can define, teach and apply whatever new human perception skills are needed.. For now, the best we can do is turn away from the worst aspects of social media and much of its content.

          1. Me too! I have just enough psychological awareness of the technologically-induced problems to perceive their massive scope on us all, but I have none of the tools needed to organize and analyze it.

            However, I have invested hundreds of hours as a volunteer STEM tutor/mentor for disadvantaged high school students, and I came to see how the next generation deals with our new environment in ways fundamentally different from me and my generation. I wish I could enumerate the differences, but my general impression was they were coping with it far better.

            I believe they may be the ideal place to start our search. If only we can get them to set aside their addiction to Fortnite and PUBG and talk with us…

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