Human and Animal Vision

April 18, 2014

It turns out that humans are highly anthropocentric in how we conceive of vision. The measures that we use tend to be areas where problems in human vision arise: focusing at distant and close range, seeing at night, depth perception, field of vision, and colorblindness. We don’t factor in things that most humans can do easily, such as recognize patterns, and we also don’t think about things we can’t do at all, such as recognize the source of diffuse light.

Here is a list of factors that vision entails (which may not be complete):

Ability to detect light (this is the core function of vision)

Ability to locate the source of diffuse light (polarization)

Ability to see in low light

Ability to see in bright light

Sensitivity to changes in contrast

Ability to see colors

Range of color vision

Ability to distinguish hues within a narrow band of color

Depth perception

Detection of movement

Ability to see stationary objects

Field of vision (including ability to see up and down as well as on a 360 degree plane)

Focusing ability (including speed of focus on near and far objects)

Ability to detect images at great distances

Clarity of vision at far and close range (accommodation)

Ability to detect shapes, both solid and outline

Ability to recognize patterns

Rapidity of image formation (analogous to frames per second in a camera)

Clarity of underwater vision

Ability to detect images below the surface of the water from above (and vice versa)

Ability to compensate for idiosyncrasies in refraction (closely related to the factor above)

Ability to compensate for movement (self locomotion as well as movement in the environment)

Formation of a single image versus split vision

Capacity for visual organs to withstand environmental challenges such as cold, pressure, and debris

I have not been able to find information comparing abilities to see and interpret auras.

So which animal has the best vision? I was a few chapters into this book before I realized what a silly question this is. Each animal has a type of vision perfectly adapted to its environmental niche. No eye or set of eyes can function in all areas extraordinarily well, because there are a few areas that are mutually exclusive and so it’s a choice between specialization or compromise. If I did have to pick the animal with the best vision, however, it would be any member of the ape family, including humans. No doubt many will not believe me and will dismiss this as more anthropocentricism. I say this because while there are animals who outperform us in every area of vision, except perhaps pattern recognition, our eyes function competently in a wide range of environments and circumstances. Our eyes do little that is spectacular but almost everything well. This is probably the main reason we have adapted to so many environments around the globe.


Sinclair, Sandra. How Animals See: Other Visions of Our World. New York: Facts on File, 1985.

Photo credits: Eagle–Vtornet; Chimpanzee–Thomas Lersch

How Animals See

April 11, 2014

Most of us intuitively understand that other animals do not see the world the way we humans do, and we like to imagine how things look from their point of view. It turns out that the ways of seeing are more intricate and varied than we realize.

I am returning this week to a favorite topic of mine: vision. Over the next several weeks I will be sharing insights gleaned from my perusal of an out-of-print book, How Animals See: Other Visions of Our World, by Sandra Sinclair. This book examines eyesight in a wide range of creatures, from insects to mammals, sea dwellers to migrating birds.

I did not realize when I picked up this book how unique it is, really one-of-a-kind. Since it was published in 1985 the other books on the subject have been children’s books, which is par for the course. Books on the really interesting topics seem to be written for kids, not grownups. Lack of interest may not be the primary factor here, however. The subject matter is difficult, so much so that biologists and others who study in this area use words and concepts that most people have only a fuzzy understanding of. Sinclair spent years researching her material under the mentorship of Dr. Dean Yeager of The State University of New York College of Optometry, and Dr. Yaeger writes in his foreword that even he was forced to read outside his areas of expertise in order to assist with the project. This seems to be the kind of book that only a very bright journalist with generous assistance from experts could make comprehensible to the lay reader. Even so, I do not think I would have been able to understand this material had I not already read some basic books about human eyesight such as Relearning to See by Thomas Quackenbush, which I wrote about last year.

I have tried unsuccessfully to find a more up to date version of Sinclair’s work. I have found only two books that are close: a 2012 book called How Animals See the World: Comparative Behavior, Biology, and Evolution of Vision by Olga F. Lazareva et al and Animal Eyes by Michael F. Land and Dan-Eric Nilsson. The blurb at Goodreads boasts that How Animals See the World “…contains 26 chapters written by world-leading experts” and calls it “An exhaustive work in range and depth, … a valuable resource for advanced students and researchers in areas of cognitive psychology, perception and cognitive neuroscience, as well as researchers in the visual sciences.” Animal Eyes is billed by the publisher as “…a comparative account of all known types of eye in the animal kingdom, outlining their structure and function with an emphasis on the nature of the optical systems and the physical principles involved in image formation.” Both rather dense sounding texts assume a solid knowledge base in the visual sciences, which makes me appreciate Sinclair’s work all the more. I have to say, however, that I found even this book a stretch.

Over the next few months, look forward to juicy bits of trivia about some very weird ways of seeing.


Sinclair, Sandra. How Anmals See: Other Visions of Our World. New York: Facts on File, 1985.

Re-Training Vision: The Three Principles

October 4, 2013

William H. Bates, the ophthamologist who developed the principles of natural vision.
William H. Bates, the ophthamologist who developed the principles of natural vision.

The three principles of natural vision are movement, centralization, and relaxation.

Relaxation is meant in a very broad sense. The more relaxed the mind, the more clear the vision. The student who develops nearsightedness or astigmatism under a heavy courseload is tired and stressed, not “reading too much.” It is fine to read or do close work like needlepoint for long periods of time, even in low light, as long as this does not produce eyestrain. Straining to see worsens the vision, both immediately and in the long term. Relaxation improves vision, and eyestrain is reduced over time by trusting that good eyesight is natural over a wide range of conditions.

We are not parakeets, who see only in daylight
We are not parakeets, who see only in daylight. Photo Dick Daniels.
Centralization is a very interesting principle. The human eye is developed to see sharply in color and to see in very low light, two activities that are non-congruent. In order to function well in both areas, the central portion of the iris is adapted to sharp color vision, while the peripheral portion is activated in low light. Peripheral vision can detect motion quite well at all times, but it is not the portion of the eye that sees most clearly in normal light. In order to see clearly, it is important to see with the part of the eye that sees clearly. Instead of utilizing the entire visual field to “see everything at once,” the person with good vision moves her eyes constantly, mapping the area in front of her by looking at one thing at a time. This principle really goes back to the idea of relaxation, since it is a type of hypervigilance that creates the compulsion to try to see too much at once.

The principle of centralization is obviously related to the principle of movement, but there are some implications to this principle that are not so obvious. Movement here is a broad term, related not only to eye movement but to blinking, moving the head, and changing the posture. It is unnatural for humans to sit stiffly or to stare without blinking, and this creates eyestrain and eventually fatigue. A relaxed posture contains movement.

We are not cats, who stay motionless for long periods
We are not cats, who stay motionless for long periods. Photo Horatiotorquez.
But proper eye movement also creates a condition that is anxiety provoking for some people: it creates the perception that objects known to be stationary are actually moving. Nearly everyone is unaware of this. People with normal vision need to have this demonstrated to them with special eye exercises. Interestingly, people with poor vision will usually compensate in order to not see the movement when doing the exercises. For these people, beginning to see “stationary” objects move while doing the exercises is a sign that they are relaxing into normal eye movement.

What are the implications for inner vision? I have found that these principles carry over into other areas. It is important to be relaxed in order to see on the inner plane. It is no accident that people tend to have more visions before drifting off to sleep or while doing ordinary activities such as taking a shower. It is important to let go of the compulsion to understand everything at once and allow the vision to naturally unfold. Trying to see everything at once inhibits the inner vision as well as the outer. It is most important to develop a frame of mind which allows perceptions to occur even when a part of the brain disagrees. The mind can draw its own conclusions, but it does not need to protect itself from the information it gathers.

Seeing More Clearly

September 20, 2013

Photo by Vtornet.
Photo by Vtornet.

Many people compare the eyesight of humans unfavorably to that of other animals, but actually we are quite visual animals with the excellent eyesight that reflects this. True, we cannot see small objects from great distances like the Peregrine Falcon, we do not have the huge visual field of the owl, we do not have the hair trigger motion detection of the cat, we cannot see in two directions like the deer, we do not have the excellent low light vision of the fox, and we cannot discern the wide color spectrum of the parrot. What we do have is highly acute adaptable vision suitable for a variety of purposes. We can see well at night in low levels of light, yet our diurnal vision can detect a variety of color. We excel at tasks requiring close vision, yet we can focus on objects miles away. Our ability to detect motion, while not rivaling that of the cat, is something we rely upon. It is instinctive and natural for us to have a clear visual mapping of our surroundings at all times. In short, though we can take no prizes in any particular aspect of vision, we are competent in a variety of areas, which is in itself remarkable.

The core belief of natural vision is that it is natural for humans to have good vision, and poor vision occurs not through the passage of time or any particular activity, but through disease and, especially, poor vision habits. Poor vision is usually an acquired trait that requires practice. Improving eyesight occurs through understanding and utilizing good vision habits – not, as commonly believed, by practicing “eye exercises” a certain number of minutes per day. As one vision teacher explained to me, “I expect my students to practice no more and no less than twenty-four hours a day.”

When I first began exploring natural vision, I was advised that “The most important thing you can do is to throw away your glasses.” I was horrified. The Department of Motor Vehicles had decreed that I needed glasses in order to drive legally, and I wondered how I could negotiate a long list of situations without sharp vision. “Throw away your glasses in order to throw away your glasses” – like so much of natural vision it seemed counterintuitive. I had expected my eyesight to gradually improve, and in the course of this improvement to gradually dispose of my lenses or gradually lower the strength of the prescription.

I was unable to stop wearing glasses entirely right away, but I did begin driving less and using my lenses only in situations where they were essential (which turned out to be less frequently than I expected). I did nothing else at first to correct my vision, and I would estimate that it improved 80% over the course of a year or two through this step alone. In hindsight I understand that this was not entirely due to my eyes readjusting to focusing on their own. There were deeper psychological changes occurring that were also changing my perception. We see with our mind as well as our eyes. For one thing, I let go of the idea that my glasses were an essential part of me. I also became comfortable with the fact that vision is not static: it is clearer some days and foggier others. I let go of the idea that I must have sharp vision at all times, and paradoxically letting go of that need sharpened my vision. Most importantly, I stopped expecting my vision to naturally deteriorate with time and began trusting my eyes to continue serving me.

In future posts on this topic I will describe some key insights of good visual habits and how they apply to divination and inner vision. In the meantime, consider the implications of the idea that letting go of the need to see sharpens the vision.