All Perception is Fundamentally an Illusion

Most people who stare at the image below will believe the dark oval in the middle is growing larger. But, believe it or not, it is just an illusion – a static image.

According to a study published in the journal Frontiers in Human Neuroscience, this illusion has something to teach us about how our brains and eyes collaborate to see the world. Researchers tested the illusion on 50 men and women with normal vision and found that those participants who had eyes with the strongest pupil dilation response had the greatest response to the illusion; while those with poor dilation response could not see it.

The pupils in the human eye are designed to automatically adjust to the surrounding light, dilating when it is dark so they can capture more light, and constricting when it is bright to prevent overexposure. Even though the hole in this illusion is not darkening, the perception or expectation in our mind that it should be darkening is enough to make our pupils respond.

Bruno Laeng, a psychology professor at the University of Oslo and an author of the study, says: “There is no reason that the pupil should change [while looking at this image], because nothing is changing in the viewers world, but something clearly has changed inside the mind.”

The researchers hypothesize that the illusion is deceiving because the gradient on the central hole makes it look to the viewer as if they are entering a dark hole or tunnel, which prompts the participants’ pupils to dilate. Our brains are making assumptions about what it sees based on past experience and is trying to predict and prepare our senses for what it thinks will happen next.

It takes time for light to reach our sensory organs and send the image to our brain. The brain then takes more time to process the image, make sense of it, and decide what actions to take based on the collected information. By the time our brain catches up with the present, time has already moved forward, and the user’s environment has most likely changed.

To minimize this image collection and processing delay, the brain may be constantly trying to predict a little bit into the future so that it can better perceive the present. Being fooled by this expanding hole illusion is not a flaw of the human species, but a feature. It is most likely built up from evolutionary history to help humanity survive.

The information we get from our senses is spotty and incomplete, so the brain has evolved over time to try to guess what is happening in the uncertain and ever-changing world – and to make decisions based on what is most likely to happen next.

People who possessed brains with the best ability to adapt and predict what is happening at any given moment most likely had an advantage over those that lacked the capacity to adapt. When the illusion image is communicated to the brain, it anticipates that the body will soon be entering a dark place and it responds by telling the pupils to begin dilating (so the body will be able to react sooner in case there is danger lurking inside that black hole).

Researchers tell us that everything we perceive is inconsistent with the physical reality of the world. It is not just that the information taken in by our senses can be misunderstood, it is also that there is a universe of information available in the physical world that is imperceptible to the human senses.

Consider light itself. The light our human eyes can detect is only a sliver of the total amount of light that’s out there. The 0.0035% of the electromagnetic spectrum we can see is referred to as visible light, but the other 99.9% percent of the spectrum consisting of radio waves, microwaves, infrared radiation, ultraviolet rays, X-rays and gamma rays are all undetectable by our eyes.

Electromagnetic Light Spectrum

Humans have cone-shaped cells in our eyes that act as receivers specifically tuned to the wavelengths in the narrow visible light band of the spectrum. Other portions of the spectrum have wavelengths too large or too small and energetic for the biological limitations of our perception.

Evolution has not endowed us with the ability to see beyond the visible region of the electromagnetic spectrum; although it is possible to feel infrared radiation as heat and employ other parts of the electromagnetic spectrum for practical uses, such as X-Ray medical imaging.

But we carry on with our lives, oblivious to the huge spectrum of electromagnetic waves present all around us. Humans have managed to survive and reproduce despite our limited view. It’s a good thing that visible light was adequate to help our ancestors detect predators that would do them harm.

But imagine if our eyes were able to detect other parts of the electromagnetic spectrum — our universe would be unrecognizable. We could glean so much more visual information if we were able to see in the radio, infrared or even X-ray regions of the electromagnetic spectrum.

Bees and butterflies are examples of organisms that can detect Ultraviolet radiation. Some flowers have special markings that can only be seen in UV light. Bee and Butterfly eyes are able to view this electromagnetic radiation like lights on an airport runway, to find their way to the flower’s nectar. Snakes have special sensory organs on the front of their heads that let them ‘see’ infrared waves, which they put to use with particular effectiveness when hunting for warm-blooded prey.

Consider our sense of sound. Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz, though the upper limit in average adults is closer to 15–17 kHz (because humans lose some high-frequency sensitivity as they mature).

That range of sounds allows humans to hear many of the sounds produced in nature, but not all. Any frequency that is below the human range is known as infrasound. It is so low that it may be detected only by a creature with big ears, such as an Elephant or by specialized instruments designed by scientists to detect the low frequency sounds that precede avalanches and earthquakes. Any frequency that is above the human frequency range is known as ultrasound. Bats and Dolphins use ultrasound frequencies as high as 200,000 Hz to help them navigate via echolocation.

Most dogs can hear sound frequencies as high as 47,000 to 65,000 Hz which is far too high-pitched for humans to hear. That is why dogs can be trained to detect when their owner is about to experience a seizure. Dogs ears are also much more sensitive to loud sounds than ours, which is probably why fireworks, thunderstorms and vacuum cleaners send them scurrying for cover.

Consider our sense of smell. Humans have 396 olfactory receptors which are employed to help us pick up scents. Almost all animals, however, have a larger number of olfactory receptors than humans (rabbits have 768 olfactory receptors) which provides them with an excellent ability to smell. 

Among the animals with the greatest sense of smell are bears whose sense of smell is 300 times better than humans and is capable of detecting a deceased animal from up to 20 miles away; elephants who can smell water sources from up to 12 miles away; sharks who can smell the presence of a drop of blood in almost 100 liters of water; and bloodhounds whose sense of smell is 2,100 times better than that of a human’s and can detect trace amounts of drugs and explosives inside packages.

When you consider all these blind spots in our senses, it is obvious that humans live in a world in which many sights, sounds and smells exist that are beyond the ability of our limited senses to detect; and those that we can detect can be compromised by our overactive minds. It’s enough to make you think that all human perception is, fundamentally, just an illusion; or as Bob Dylan keenly observed “All the truth in the world adds up to one big lie“.

It could well be that we are each living in our own virtual reality world, bound by the limitations of our physical senses and the tricks employed by our minds. Dr Laeng believes we each do live in a virtual reality world. Much of what we see is an illusion, but we are not really being tricked – he believes the visual illusions help to reveal the mismatches between what our eyes see and what our mind’s eye thinks is happening.

So what lessons can we take away about how to live our lives knowing the limits of our senses and the tendency of our brains to trick us into seeing what it wants us to see.

One lesson is that we should remind ourselves that things are not always what they appear. It is possible for two people to witness the same event but still give contradictory descriptions of what they saw; even though they are certain their description of events are true. Knowing that our eyes are susceptible to being tricked should make the criminal justice system wary of judging guilt based solely on the testimony of eye-witnesses.

Another lesson is to be careful of letting our minds be swayed by our pre-conceived biases and political opinions. If we each live in our own virtual worlds then we need to be careful of falling into the trap of accepting information that matches our biases and opinions while discarding facts that don’t. If more people were careful to seek out an objective, agreed-upon, reality then maybe there would be less disagreement and discord in today’s society.

Finally, we should all be humbled and filled with wonder knowing that what our senses reveal to us is only a small portion of the great wide-world we live in. There is a whole universe out there beyond our human senses – a twilight zone if you will, a dimension not only of sight and sound but of the mind, one where there is so much more for us to discover.

The Eye is the Jewel of the Body

I have been battling a stubborn eye infection for the past 6 weeks. It started with symptoms of redness, swelling, weeping and tenderness in my left eye. Within two weeks my right eye also became infected – eventually becoming worse than my left eye.

To complicate matters, this infection happened to occur during the peak of the coranavirus pandemic – which made it very challenging to meet with doctors and schedule health care appointments.

I managed to book a remote tele-health appointment with my primary care physician, who guessed that I had some form of bacterial conjunctivitis. He prescribed a 7 day course of both oral and eye drop antibiotics that he believed would clear up the infection.

At the end of my seven day treatment, however, my eye infections were really no better. I scheduled a second tele-health visit with another physician who prescribed a different eye drop treatment that contained a more powerful antibiotic.

As soon as I began the new treatment my eye condition became dramatically worse . My eyes began to water constantly and the eyelids became so inflamed and swollen that I could barely open them. My eyes looked and felt as though they had been through a losing 15 round boxing match.

Panicking a little at this development, I began to put double doses of the eye drops in my eyes, hoping that the extra antibiotics would hasten my recovery from the infection. But this only seemed to make my condition worse.

At this point, my doctor recommended that I visit my nearest Urgent Care facility to have my eyes examined. The doctor there believed that my body was having an allergic reaction to the antibiotic eye drops which was causing my eyelids to swell and my eye ducts to become clogged. I was told to discontinue my current treatment immediately and see an eye specialist.

Fortunately, I was able to get an office appointment with an eye doctor who looked at my eyes under a microscope and swabbed them to determine what type of bacteria was the culprit. Based on the examination, I was prescribed a combined steroid/antibiotic treatment and instructed to regularly massage my eyes with hot compresses to help open up the clogged eye ducts.

It was a relief when my eyes began to slowly improve under the positive effects of this new treatment and I am thankful that my eyes have almost returned back to their normal condition.

The whole experience though has given me a greater appreciation of the role the eyes play in our daily life and how important they are to our overall well-being. As Shakespeare observed in Romeo & Juliet “He that is stricken blind can not forget the precious treasure of his eyesight lost“.

Picture Courtesy of Colin Maynard @invent

A number of emotions and concerns took root in my mind while I was battling the course of this malady:

Vanity – According to Henry David Thoreau “The eye is the jewel of the body” and the eyes are indeed the focal point of human relationships – and usually the first thing we notice when we encounter somebody new. It is considered a sign of respect and good manners in our society to look directly into a person’s eyes when you greet them.

So you can imagine that during my ailment I became very self-conscious of my appearance and was reluctant to be seen in public without covering my eyes with sunglasses. My own wife suddenly shrank from my embrace and jokingly began calling me lizard eye.

Because one of the symptoms of the Covid-19 virus happens to be inflamed eyes, the people I encountered seemed to become especially nervous around me. Believe me when I say that once people had a good look at my face they went out of their way to keep socially distant from me.

Fear – As my eye condition continued to deteriorate and stubbornly resisted all forms of treatment despite the use of powerful antibiotics, I began to experience feelings of fear and anxiety over the inability to use my eyes during my everyday routines. I started wondering if there were a real possibility that the illness might cause some kind of permanent damage to my eyesight.

My right eyelid became so swollen that I could only pull it open using my fingers and both eyes watered so much that my vision became very blurry. It became difficult and uncomfortable to do all the everyday ordinary things that requires functioning eyesight (like reading a book, watching a show, working on the computer or tying a fishing knot).

It forced me to consider in the back of my mind how different life would be and how my daily activities would need to change dramatically in order to live with diminished eyesight.

Magnification of other senses – Studies have shown that people who are blind tend to have enhanced abilities in their other senses. Detailed brain scans comparing the brains of people who are blind to the brains of people who are not blind show that individuals with impaired sight have heightened senses of hearing, smell and touch.

I’m not claiming that my other senses increased to superpower levels to compensate for the deterioration of my eyesight – my loss was too short term to re-wire my brain – but what I can say is that my malfunctioning sense of sight caused me to focus more on my other senses and to derive increased pleasure from them.

I closed my eyes and amused myself by listening to music and audio books, I delighted more in the smell of the pleasant scents wafting in the breezy Spring air and in the satisfying mix of flavors in my food, I relished the feel of soaking in the tub and submerging my tender eyes in the warm water.

Now that my eyes are on the mend I must remember that I am failing to appreciate the fullness of life when I let one or more of my senses dominate at the expense of the others.

Simultaneously employing all our senses in concert to their full capacity helps us to live our life in High Definition with Surround Sound quality rather than the limiting Black & White and Mono soundtrack experiences that are provided by the individual senses.

Compassion and Empathy – When we are in the bloom of health, it is human nature for us not to think about the difficulties that other people living with disabilities and impairments must face during the course of their daily life.

My brief encounter with sight impairment gave me a new appreciation for people who must live permanently with one or more disabilities that makes living inconvenient and challenging.

We are told it is a healthy practice to count our blessings and to have a grateful heart. Most people when they count their blessings only think about how grateful they are for the good things in their life. This experience has reminded me that it is equally important for me to be thankful for the afflictions that I have been spared.

When our lives are not burdened by birth defects, diseases, sicknesses, poverty or addictions we find it difficult to show compassion or relate to those who struggle with one or more of these issues every day.

It is good every now and then to put yourself in the shoes of those who are walking a hard road and to remind yourself how you would like to be treated if you were in their shoes – because someday you may be.

As unpleasant as my adventure with this eye infection has been, it has also been a positive learning experience because it has given me a new perspective about the vanity of vanity, forced me to confront and overcome my fears, reminded me to use all my senses to their full capacity and encouraged me to treat with compassion all those who are living with handicaps.

I know that my eyes will eventually fail me as I age, just like the rest of my body will, but I do believe the overall vision I gained from this experience will stay with me until the very end.